Theses and dissertations (Applied Sciences)

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Antioxidant and antihypertensive activities of bioactive peptides derived from fish collagen and milk lactoferrin
(2025-05) Elisha, Cherise; Pillai, Santhosh Kumar Kuttan; Bhagwat, Prashant
Bioactive peptides (BPs) are short sequences of amino acids known for their physiological benefits, including antioxidant, antimicrobial, antihypertensive, and antidiabetic properties. BPs can be derived from various food proteins; from plant, meat, milk, and marine sources, through methods such as microbial fermentation or enzymatic hydrolysis. This study explored the potential of BPs derived from milk lactoferrin (LF) and fish collagen using in silico and in vitro analyses. The inhibitory potential of BPs derived from LF, a multifunctional milk glycoprotein found in bovine and human milk, against angiotensin-converting enzyme (ACE) and dipeptidyl peptidase-IV (DPP-IV) enzyme were analysed. Initially, in silico digested bovine and human milk-derived-LF sequences were screened for potential ACE and DPP-IV inhibitory activity using AHTpin and StackDPPIV, respectively. Molecular docking results revealed that bovine LF peptides ‘EPYF’ (−10.1 kcal/mol) and ‘WQWR’ (−9.3 kcal/mol) had significantly lower binding energies with ACE and DPP-IV, respectively. In addition, in vitro analysis of bovine LF hydrolysates demonstrated IC50 values of 0.48 ± 0.01 mg/ml (ACE) and 0.93 ± 0.02 mg/ml (DPP-IV). Liquid chromatography-mass spectrometry (LC-MS/MS) analysis identified the peptides ‘EPYF’ and ‘WQWR’ which are potential inhibitors of ACE and DPP-IV, respectively, present within the parent peptide sequences of the bovine LF hydrolysates. These findings suggested that bovine LF peptides, due to their bioactive potential and functional similarities to human LF, may serve as a viable alternative to human LF. Subsequently, the research evaluated the inhibitory potential of BPs derived from fish collagen. The first step involved extracting collagen from the pretreated snapper salmon skin using an acid-solubilisation technique, followed by characterisation through biophysical analyses, such as SDS-PAGE and CD spectroscopy. Thereafter, the extracted collagen was hydrolysed using a pre-digestive approach. Papain was used as the pre-digestive enzyme due to its broad specificity, which effectively breaks down collagen and releases a range of BPs. Pepsin and trypsin were also key enzymes utilised in the in vitro digestion process to mimic human gastrointestinal conditions, since they are present in the stomach and small intestine, respectively. In this regard, snapper salmon skin collagen was hydrolysed using two approaches: pre-digestion followed by pepsin-trypsin digestion (PDPTD) and pepsin-trypsin digestion alone (PTD). This yielded fish collagen hydrolysates (FCH), and the peptides were fractionated using various cut-off membranes (<3 kDa, 3–10 kDa, and >10 kDa). xv The FCH that did not undergo pre-digestion exhibited IC50 values of 0.54 ± 0.03 mg/ml (ACE inhibition), 2.25 ± 0.02 mg/ml (DPP-IV inhibition), and 0.04 ± 0.01 mg/ml (ABTS antioxidant activity). In contrast, pre-digested FCH showed lower IC50 values of 0.33 ± 0.06 mg/ml, 1.67 ± 0.08 mg/ml, 2.38 ± 0.31 mg/ml, and 0.03 ± 0.00 mg/ml for ACE inhibition, DPP-IV inhibition, DPPH antioxidant activity, and ABTS antioxidant activity, respectively. FCH (from both PDPTD and PTD methods) were subjected to peptide identification and the identified peptides underwent in silico analyses to assess their physicochemical properties and potential bioactivities. Molecular docking analysis of pre-digested FCH peptides identified the peptide, IGFPGFPG, with significant ACE and DPP-IV inhibitory activities, exhibiting low binding energies to ACE (−11.2 kcal/mol) and DPP-IV (−9.1 kcal/mol). The study concluded that pre digested collagen peptides demonstrated improved bioactive potential, as reflected by their lower IC50 values and docking score. Overall, the study concluded that BPs derived from bovine milk LF and fish collagen have potential as antioxidants and inhibitors of ACE and DPP-IV. These findings underscore their potential for use in developing dietary supplements and functional foods, which could offer a myriad of health-promoting properties.
Exploring phenolics against penicillin-binding proteins as druggable targets in antibacterial therapy : a structure-activity relationship study
(2025-09) Aribisala, Jamiu Olaseni; Sabiu, Saheed; Makhanya, Talent Raymond
Alterations in penicillin binding proteins (PBPs) coupled with inactivation of beta-lactam scaffold by beta-lactamase remain the major basis for the broad clinical resistance to beta– lactam antibiotics. While enzyme modification is most common with Gram-negative bacteria, alteration in key PBPs is prevalent in Gram-positive organisms and increasingly being reported in Gram-negative bacteria. Modification of PBPs ensures that the interaction with beta-lactams occurs at a considerably higher antibiotic doses than with PBPs from susceptible strains, thus substantially reducing biological activity. Consequently, developing potent therapeutics with a different scaffold against PBP druggable targets represents a viable alternative strategy against resistance to beta-lactams. Phenolics, aside having a different scaffold from conventional betalactams, have been reported to be effective against various multidrug-resistant Gram-negative and Gram-positive bacteria. The characteristic hydroxyl group of phenolics are implicated in strong PBPs binding while having the capability to auto-oxidize in the presence of transition metals to generating reactive oxygen species (ROS) which have been implicated in the lethality of most conventional antibiotics, including beta-lactams. These intriguing characteristics of phenolics position them as a viable source of drug candidates that can be developed as alternative beta-lactams. Hence, this study employed a multifaceted in silico and in vitro approach in bioprespection for phenolics as modulators of PBPs and ROS in an effort to manage resistance to beta-lactams due to PBP modifications. Using a structure-based drug design (SBDD) approach involving the use of pharmacophore screening and molecular docking, the over 10,000 currently known phenolics were screened at the active site of key PBPs of common and clinically important Gram-positive (Staphylococcus aureus and Streptococcus pneumoniae) and Gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacteria. The identified top-20 phenolics against each of the investigated key PBPs (PBP2a of S. aureus, PBP2x of S. pneumoniae, PBP3 of P. aeruginosa and PBP3 and 5 of E. coli) had higher negative docking scores relative to the four beta-lactams (amoxicillin, cefotaxime, aztreonam and doripenem) reference standards suggesting effectiveness of the adopted SBDD approach. Subsequent filtering of the top-20 leads in each case based on their physicochemical, pharmacokinetic and toxicological profiles afforded topfive phenolics that are chemically diverse, orally bioavailable and with good synthetic feasibility scores (<5) appropriate for drug development. The profiled top-five compounds against the key PBPs in each case were further subjected to 120-ns molecular dynamic (MD) simulations using the in-house HEAL1361 programme with Amber 18 package of the CHPC (Centre for High Performance Computing), South Africa. The identified lead phenolics with the highest negative binding free energy (ΔGbind) in each case of the essential PBPs, which include silicristin (PBP2a active site: −25.61 kcal/mol and PBP2x allosteric site: -50.54 kcal/mol), epicatechin gallate (PBP2a allosteric site: −47.65 kcal/mol), lysidicichin ( PBP3 of E. coli: −41.66 kcal/mol), epigallocatechin 4-benzylthioether (PBP5 of E. coli −38.97 kcal/mol), catechin 3-rhamside (PBP3 of P. aeruginosa: -28.99 kcal/mol), and epicatechin 3- O-(3-O-methylgallate (PBP2x active site: -42.18 Kcal/mol), all had higher negative binding free energy than the reference standards. Except for silicristin with lesser stability [higher root means square deviation (RMSD)] against three of the essential PBPs [PBP2a (5.65 Å) of S. aureus, PBP3 (3.97 Å) of E. coli and PBP2x (4.90 Å), of S. pneumoniae], all the lead phenolics had better stability (< 3 Å), compactness and flexibility relative to the referenced standards and other top-five phenolics in each case of the investigated PBPs. However, silicrsitin remain the only lead phenolics with broad spectrum ΔGbind for all the essential PBPs, suggesting that the lesser stability of the compound with three of the essential PBPs could be improved to enhance stability. Moreso, as the focus of this study is to identify lead phenolic with wide spectrum activity against the investigated bacteria. Thus, for subsequent analysis, silicristin was selected for structural optimization against the essential PBPs for the possibility of yielding novel drug candidates with improved antibacterial efficiency, higher stability, reduced toxicity and favorable pharmacokinetic properties relative to silicristin. Improved thermodynamic stability has been demonstrated to be critical in affinity/potency of a drug for a target and its subsequent efficacy in vitro and in vivo. This study employed hybridization of pharmacophore and structural simplification techniques in the enhancement of thermodynamic stability of silicristin against the key PBPs of the investigated bacteria. The knowledge of the interactions of silicristin with the key PBPs of the organisms was employed in designing 25 novel derivatives of chalcone bis-coumarin from easily synthesizable starting materials of coumarin moieties. Following molecular docking, pharmacokinetic screening, MD simulation and energy refinement of the 25 derivatives, RD2c (PBP3 of E. coli: -46.26 kcal/mol), RD1c (PBP3 of P. aeruginosa: -39.42 kcal/mol and PBP2x active site: -42.90 kcal/mol), RD1a (PBP2a active site: -37.56 kcal/mol), D1a (PBP5 of E. coli: -37.19 kcal/mol), D1h (allosteric site of PBP2a: -53.09 kcal/mol and PBP2x of S. pneumoniae:-38.53 kcal/mol), were identified as best derivatives with enhanced ΔGbind, stability, and pharmacokinetics properties relative to silicristin. Quantum calculations using DFT B3LYP/6-31G+ (dp) techniques further showed that these derivatives are more reactive and with higher ability to form hydrogen bonds due to their higher electrostatic potential compared to silicristin. Except for PBP2x, this observation is consistent with the bond analysis of each complex post-MD simulation as the best derivative in each case of the PBP formed higher number of hydrogen bonds compared to silicristin. The exploration of catechol, resorcinol, and hydroquinone either alone or in combination with each other at either end of the derivatives promotes good pharmacological properties, while the presence of a pyrogallol and/or a benzene ring with more than two hydroxy group at one or both ends of the derivatives caused reduced oral bioavailability relative to silicristin. The synthetic accessibility of the derivatives was exploited by synthesizing the parent compound of the best derivative using Knoevenagel condensation, Vilsmeiers Haack, and Aldol condensation reactions. The successfully synthesized parent compound was subjected to nuclear magnetic resonance (NMR) for structural elucidation and was further validated using the gauge independent atomic orbital (GIAO) method. Expectedly, significant improvement in binding capacity and pharmacokinetic properties was observed with the best derivatives relative to silicristin; an observation that could translate to enhanced potency in vitro and in vivo. Silicristin is one of the bioactive compounds of silymarin, a standardized extract from the dried seeds of milk thistle which has been shown for its PBP modulatory properties in silico. Thus, to understand the mechanism of action of silicristin in vitro, this study investigates the antibacterial properties of silicristin and the synthesized parent compounds of the best derivatives of chalcone bis coumarin (PSCB) derived from silicristin against sensitive and resistant strains of Gram-positive (S. aureus and S. pneumoniae) and Gram-negative bacteria (E. coli and P. aeruginosa). Also, the possible involvement of ROS in the lethality of silicristin, PSCB and reference beta-lactams (amoxicillin against Gram-positive organisms and cefotaxime against Gram-negative bacteria) was also investigated. The minimum inhibitory concentration (MIC) assessment showed that silicristin, PSCB and reference beta-lactams had higher MIC values against the resistant strains [cefotaxime (2 – 16 µg/mL), amoxicillin (4 – 32 µg/mL, silicristin (8 – 64 µg/mL) and PSCB (16 – 128 µg/mL)]. The highest MIC for silicristin, PSCB and reference beta-lactams was observed against the resistant and sensitive strains of P. aeruginosa [sensitive strains (8 – 64 µg/mL), resistant strains (16 – 128 µg/mL)], while the lowest MIC was found in S. pneumoniae [sensitive strains (0.5 – 8 µg/mL), resistant strains (2 – 16 µg/mL)]. Compared to silicristin (4 – 64 µg/mL), PSCB (8 – 128 µg/mL) exhibited higher MIC values against all the test strains and the antibacterial activities were observed to occur in a concentration- and time-dependent manner. Except against the sensitive and resistant strains of E. coli where silicristin had a comparable killing effect as cefotaxime, silicristin had a better killing rate than PSCB and reference standards against all the test organisms with the best effect observed between 8 – 14 h after treatment. Except for the exploration of silicristin and amoxicillin against the resistant strain of E. coli, which was found to be addictive, the combinatorial therapy showed that silicristin had a synergistic effect with both amoxicillin and cefotaxime against all test organisms. This could mean that silicristin had other mechanism of antibacterial effect different from beta-lactams. In contrast, PSCB with cefotaxime and amoxicillin had only synergistic effects against resistant strains of Grampositive organisms suggestive of a similar mechanism of action for PSCB and the test betalactams. A further probe into the ROS generating potential of the antibacterial agents using ROS-specific dyes, showed that while PSCB and reference beta-lactams caused significant (P < 0.05) higher generation of superoxide ion (O2 •−), silicristin conversely enhanced higher (P < 0.05) generation of the most toxic ROS form, the hydroxy radicals ( •OH), which is often produced via the Fenton reaction. This observation with silicristin suggests its enhanced modulatory effect on Fenton reaction relative to PSCB and the standards and further facilitated increased NAD/NADH ratio, ADP/ATP ratio, lipid peroxidation, carbonyl content, propidium iodide (PI) uptake, and depletion of reduced glutathione as observed with silicristin-treated cells. This observation points to the enhanced involvement of oxidative stress in the modulatory effect of silicristin against all the test organisms compared to PSCB and the reference standards. This enhanced oxidative stress in silicristin-treated cells was substantiated with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) micrographs with cell walls with more blisters, eruptions, and sores compared to the observed effects with other treatments and the untreated cells. Oxidative stress was also noted to facilitate SOS (Save Our Souls) response in upregulating SordA and SoxR, with the most prominent effect observed with silicristin in a manner that is more evident in the sensitive strains relative to the resistant strains. Taken together, these observations points to the enhanced redox effect of silicristin on the sensitive and resistant strains of both Gram-positive and Gram-negative organisms relative to PSCB and reference beta-lactams and could be explored to develop novel alternative therapeutics to beta-lactams in the treatment of infections caused by the test organisms. Additionally, since the best derivative in each case of the essential PBPs had a similar synthetic route as PSCB, it is recommended that the synthetic route be adopted in the synthesis of the best derivatives to enable the investigation of their in vitro and in vivo antibacterial activities for the possibility of subsequent development as beta-lactams.
Evaluation of anti-ageing potential of lemongrass tea and its mechanisms of action
(2025-09) Kazeem, Mutiu Idowu; Sabiu, Saheed; Mellem, John Jason
Ageing is a complex process that involves the loss of physiological integrity and negatively impacts the well-being of an organism. It is associated with various diseases such as hypertension, cardiovascular and neurodegenerative diseases. However, the proportion of geriatrics is increasing globally, and they are susceptible to these diseases. Regrettably, there is no known medication for managing ageing and its associated complications. One of the plants that is widely consumed as tea is lemongrass (Cymbopogon citratus) due to its aroma and refreshing taste. Several studies have reported the pharmacological properties of lemongrass, but there is no information on its effect on ageing. Therefore, this study investigated the anti-ageing properties of Cymbopogon citratus (lemongrass) tea using in vitro, in silico and in vivo techniques. Fresh and dry lemongrass infusions were subjected to proximate, mineral, amino acid, and phytochemical analysis using Inductively Coupled Plasma Mass Spectrometry (ICP-MS), high-performance liquid chromatography (HPLC), and Liquid Chromatography – Mass Spectrometer (LC-MS). This was followed by the determination of the antioxidant, anti-ageing and neuroprotective potentials of the lemongrass infusion using in vitro methods. Computational techniques, including molecular docking, molecular dynamics simulation and pharmacokinetic profiling, were employed to probe the possible mechanism of anti-ageing effects of the lemongrass teas. The in vivo anti-ageing property of the lemongrass teas was evaluated by including different concentrations of the teas in the diet of D-galactose-induced ageing in Drosophila melanogaster for 14 days, followed by determination of both biochemical and molecular parameters. The results showed that both fresh and dry lemongrass teas are rich in nutrients and phytochemicals. While both lemongrass infusions have similar neuroprotective effects in vitro, the dry lemongrass infusion exhibited better antioxidant activities (with lower EC50 values for DPPH, hydroxyl and superoxide radicals), and these are comparable to the reference standard, gallic acid. It also displayed better anti-ageing properties (with lower IC50 values for inhibition of collagenase, elastase, hyaluronidase and tyrosinase) similar to the standard, oleanolic acid. In the in-silico studies, kaempferitrin had the lowest binding energy for collagenase (-41.57 kcal/mol) and hyaluronidase (-52.09 kcal/mol), while lonicerin and isovitexin-2”-O-arabinoside possessed the lowest binding energies for elastase (-35.55 kcal/mol) and tyrosinase (-53.09 kcal/mol), respectively. Kaempferitrin displayed the highest number of stable interactions with collagenase and hyaluronidase, while limocitrin-7-(6”- acetylglucoside) and isovitexin-2”-O-arabinoside interacted more with elastase and tyrosinase, respectively. The resulting complexes formed with chamaemeloside (-66.59 kcal/mol), isocarlinoside (-65.79 kcal/mol), neocuscutoside C (-41.09 kcal/mol), and aspulvinone H (-72.28 kcal/mol) against acetylcholinesterase, butyrylcholinesterase, β-secretase and monoamine oxidase, respectively, had the lowest binding free energy values compared to the respective standards. However, benzyl alcohol β-D-rutinoside, kaempferitrin, neocuscutoside C and aspulvinone H possessed the most stable interactions with acetylcholinesterase, butyrylcholinesterase, β-secretase and monoamine oxidase, respectively. The D-galactose-treated flies experienced significant distortion (p ˂ 0.05) in their antioxidant status and enzymes (catalase, superoxide dismutase and glutathione peroxidase). However, the inclusion of dry lemongrass infusion in the diet restored all the alterations witnessed in the D-galactose flies. The dry lemongrass infusion also upregulated the SOD1, CAT and dFOXO genes while downregulating the DILP2 gene. It can be concluded that both fresh and dry lemongrass infusions are rich in nutrients and phytochemicals, with the dry infusion displaying better antioxidant and anti-ageing properties in vitro. This is confirmed by the in vivo studies where the dry lemongrass infusion was more effective in ameliorating ageing-related complications in Drosophila melanogaster. Though the phytochemicals present in both teas are similar, they are more abundant in the dry tea, which may account for its more potent activities. These phytochemicals include lonicerin, chamaemeloside, kaempferitrin and neocuscutoside C. Consequent upon the outcome of this study, a ready-to-drink beverage may be developed from the dry lemongrass while its bioactive compounds are isolated for future drug development.
Synthesis and characterization of amine functionalized cellulose-silica composites for heavy metal adsorption from contaminated water
(2025-09) Mazibuko, Mayenzeke Trueman; Mokhothu, Thabang Hendrica; Mdluli, Phumlane Selby; Paul, Vimla
The pressing challenge of heavy metal pollution in water sources demands innovative and sustainable solutions. This project explored recent advancements in heavy metal remediation techniques, focusing on the utilization of cellulose–silica composites and tailored surface modification techniques. The synthesis strategies and properties of cellulose–silica adsorbents highlight their enhanced adsorption capacities and structural robustness for removing heavy metal pollutants from aqueous environments. The study investigated various surface modification approaches, including thiol functionalization, amino acid grafting, and silane coupling agents, for optimizing the surface chemistry and morphology of cellulose–silica composites. Mechanistic insights into the adsorption processes and kinetics of modified adsorbents were studied, along with considerations for optimizing adsorption performance under different environmental conditions. The adsorption method for hexavalent chromium (Cr (VI) removal from domestic and industrial wastewater is widely desirable due to public health concerns about the heavy metal. The study aimed to investigate the adsorption of Cr (VI) using a novel adsorbent: an amine-functionalized cellulose-silica composite derived from banana pseudo-stem. The in-situ sol-gel method was used to create cellulose-silica silane functionalized composites and analyzed them through different characterization techniques such as attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), Brunauer–Emmett–Teller (BET), Scanning Electron Microscopy (SEM), and transmission electron microscopy (TEM) techniques. ATR-FTIR depicted key organic constituents in raw banana pseudo-stem fibers (BF) and the formation of Si–O bonds in Bleached Cellulose-Silica (BC–SiO2) composite and further enhanced by the grafting of N-[3- (trimethoxysilyl)propyl]ethylenediamine (DAPTMS) onto the BC-SiO2 surface in BC-SiO2- DAPTMS. Functionalization with varying DAPTMS concentrations (2, 4, and 10%) was employed to enhance the composites' adsorption capacity, binding affinity, and thermal stability. Comprehensive characterization using ATR-FTIR, XRD, TGA, BET, SEM, and TEM revealed structural and thermal modifications, with higher DAPTMS concentrations improving adsorption performance. The modifications of BC with SiO2 followed by DAPTMS result in the BC-SiO2-DAPTMS composite, which has reduced crystallinity as shown by XRD and enhanced thermal stability as demonstrated by TGA, while BET analysis showed altered surface area and pore characteristics in BC-SiO2-DAPTMS (2%). The SEM and TEM imaging provided visual evidence of structural modifications and improved dispersion in BC-SiO2-DAPTMS composites. The effects of initial Cr (VI) concentration, adsorbent weight dosage, contact time, and pH on the removal efficiency of Cr (VI) using amine-functionalized cellulose–silica composites were also investigated. The results highlighted significant differences in adsorption performance based on the composite formulation and operating conditions. The initial Cr (VI) concentration effect revealed that BCSiO₂-DAPTMS (4%) consistently achieved the highest removal efficiencies, peaking at 97.14% at 0.3 mg/L. BC-SiO₂-DAPTMS (10%) followed closely, with efficiency stabilizing around 95.53% at higher concentrations. BC-SiO₂-DAPTMS (2%) exhibited lower but improving performance with increasing concentrations. Adsorbent weight dosage experiments demonstrated that increasing weight enhanced removal efficiency, with BC-SiO₂-DAPTMS (10%) achieving optimal performance (95.46%) at 1 g, though benefits plateaued beyond this weight. The impact of contact time showed BC-SiO₂-DAPTMS (10%) achieving equilibrium after 50 minutes, with a maximum removal efficiency of 91.29%. BC-SiO₂-DAPTMS (4%) exhibited a similar trend, but with a slightly lower maximum efficiency of 84.30%. The pH study indicated that acidic conditions (pH 1–4) were most favourable for Cr (VI) removal, with BC-SiO₂- DAPTMS (10%) reaching the highest removal efficiency (89.27% at pH 3) and maintaining superior performance across all pH levels. Overall, BC-SiO₂-DAPTMS (10%) demonstrated the best performance across all conditions, followed by BC-SiO₂-DAPTMS (4%), underscoring the importance of higher DAPTMS functionalization for enhanced Cr (VI) adsorption. These findings offer valuable insights into optimizing composite design and operational parameters for effective Cr(VI) remediation in contaminated water systems. The kinetic modelling followed the pseudosecond order (PSO) model, while the Freundlich and Langmuir isotherms provided insights into the adsorption mechanisms. The overall results demonstrated that the BC-SiO₂-DAPTMS composites, particularly at 4% and 10% DAPTMS concentrations, are effective, scalable, and sustainable adsorbents for Cr (VI) remediation, offering significant potential for practical water treatment applications. The study offered valuable insights into the development of effective adsorbent materials for sustainable heavy metal remediation applications.
Impact of pollution sources of microplastics and associated microbial populations in surface water
(2025-09) Malambule, Nomalihle Ladyfair; Pillai, Sheena Kumari Kuttan; Amoah, Isaac Dennis
Microplastics (MPs) are ubiquitous environmental pollutants of global concern, presenting a major threat to aquatic ecosystems. The study examined the effects of potential pollution sources of MPs and associated microbial communities in riverine environments, including wastewater treatment plants (WWTPs), agricultural areas (AA), urban areas (UA), and industrial discharge (IA). The study sites were selected along the uMsunduzi River in KwaZulu-Natal, and the sampling was conducted in two seasons (summer and winter). Morphological and chemical characterization of MPs was performed using microscopy, ATRFTIR, and Pyro-GC/MS analysis. Shotgun metagenomics was used to analyze the microbial community. The potential health risks associated with selected pathogens in the biofilm were also assessed using Quantitative Microbial Risk Assessment (QMRA). Microplastics were detected in abundance from all four sites with concentrations in the IA being the highest (69 particles/L), followed by the WWTP (51 particles/L), the UA (49 particles/L), and the AA (39 particles/L). Additionally, sediment samples showed higher MP particles compared to the surface water. The most common types of MP detected were fibers, followed by pellets and fragments for both surface water and sediment samples. Furthermore, the key polymers detected via chemical characterization were polyethylene (PE), Polyethylene terephthalate (PET), polypropylene (PP), polystyrene (PS), and Polyvinyl Alcohol (PVA) across all sites with varying dominance. The PS, PET, and PE were predominant at the UA, while the WWTP and IA exhibited a variety of polymers, including PE, PP, PET, and PS. The AA site showed the presence of PE, PP, PS, PET, and PVA. Metagenomic data demonstrated a significant microbial diversity (p = 0.0012) and composition (PERMANOVA F = 16.386; R2 = 0.15, p < 0.001) in different sites (UA, WWTP, AA, and IA), and habitat (surface water and plastisphere). The plastisphere harbored a distinct microbial community compared to surface water. At the phylum level, Bacteroidetes were significantly higher in surface water, whereas α- and β-Proteobacteria dominated on the plastic surface (p < 0.05). In regard to the different sites, WWTP had the most different taxa (5), followed by UA (3), with AA and IA each having only 1 unique taxon. The distance decay model showed that microbial communities in the plastisphere and surrounding environments are significantly positively associated with the sources of pollution (UA: R² = 0.83, p = 0.015; WWTP: R² = 0.88, p = 0.0072; AA: R² = 0.85, p = 0.0075; IA: R² = 0.95, p = 0.0011). The study also revealed the presence of various antimicrobial resistant genes (ARGs) in both surrounding surface water and plastisphere, with MP surfaces showing higher ARGs than surrounding surface water. For instance, the plastisphere harbored 19 ARGs compared to 9 in surface water. The WWTP showed diverse ARGs, including the widely reported ARGs conferring resistance to tetracycline, fluoroquinolone, and aminoglycoside. The study also identified 17 pathogenic microbial species across different sites, with Acinetobacter baumannii being the most dominant. Furthermore, common pathogens such as Escherichia coli, Pseudomonas aeruginosa, Acinetobacter baumannii, and Klebsiella pneumoniae were detected across all sites, seasons, and habitats. The microbial risk assessment based on two dominant pathogens (Pseudomonas aeruginosa and Salmonella enterica) revealed that the risk of infection varied across different pollution sources and seasons. Notably, the highest infection risk associated with selected pathogens was found in IA and WWTP-impacted sites which is in accordance with the total number of MPs detected indicating and increase in MPs will have a significant impact on the associated health risks. Results of this study indicate that different pollution sources significantly influence MP abundance and types, as well as the structure of microbial communities, which may ultimately pose a threat to human health.
Remediation of efavirenz using a magnetic molecularly imprinted titania nanocomposite
(2025-09) Sibali, Asenathi; Ncube, S.; Mokhothu, Thabang H.
In the current study, remediation of efavirenz as a model antiretroviral drug in wastewater effluents was investigated using a hybrid photodegrader based on titania embed on a magnetic molecularly imprinted polymer (MMIP). Initially, a MMIP was synthesized to specifically recognize and remove efavirenz from wastewater effluents. The magnetic smart polymer was synthesized via a bulk polymerization technique with efavirenz as the template, and p-vinyl benzoic acid the functional monomer in the presence of magnetite nanoparticles. The MMIP was characterized using Fourier transform infrared spectroscopy and thermogravimetric analysis. The performance of MMIP was optimized using a central composite design. The optimum conditions for effective adsorption of efavirenz were pH 6.5, MMIP mass of 15 mg, 1 mg L-1 efavirenz concentration and contact time of 40 min. The optimal binding capacity achieved after 40 min of contact time and neutral conditions was 44.9 µg g-1 . Batch studies revealed that pseudo-second order and the Langmuir isotherm were the models that explained the kinetics and mechanism of adsorption of efavirenz onto the MMIP. This suggested that the interaction between the MMIP and the efavirenz was through chemisorption and that once efavirenz binding reaches a maximum limit, no more binding occurs. The MMIP was finally applied in the removal of efavirenz from real wastewater effluents polluted with 3.99 ng mL-1 of efavirenz. The polymeric sorbent could achieve 44.8% removal efficiencies. Reusability studies showed less than 4% average loss in the binding capacity with every reuse cycle, while there was no loss in binding capabilities when the polymer was utilized at about half its binding capacity. Finally, photocatalytic degradation of efavirenz was investigated as a potential remedial tool for efavirenz in wastewater effluents. Titania was imbedded onto the MMIP to form a hybrid MMIP/TiO2 nanocomposite with the ability to trap efavirenz from wastewater followed by its vii photodegradation. Its performance was also investigated using factorial design involving initial concentration of efavirenz (20 - 60 µg L-1 ), mass of the MMIP/TiO2 (5 -15 mg) and the time of irradiation (20 - 40 min). The results were also observed in a form of contour plots. Up to 99% photodegradation of efavirenz was achieved within 15 min. However, it was observed that the photodegrader performed better under higher concentrations of efavirenz concentrations. In general, the synthesis and optimization of a hybrid molecularly imprinted titania nanocomposite for photodegradation of efavirenz in wastewater effluents was successful. Its performance has proven that it can be a viable tool for remediation of efavirenz in wastewater effluents. Efavirenz cannot be removed by conventional wastewater treatment processes and advanced technologies such as the MMIP/TiO2 nanocomposite synthesized in the current study could help minimize the release of efavirenz into surface water systems. This work has yielded three manuscripts; a review article and two research papers. The review has been published, one manuscript is under review and the final one has been drafted.
Thermodynamic properties of deep eutectic solvents and organic solutes at different temperatures for separation of close boiling mixtures
(2025-09) Gasa, Rosemary Balungile; Deenadayalu, Nirmala; Kabane, Bakusele
The environmental impact of volatile organic compounds coupled with its cost, stability, performance, turnability and versatility of conventional solvents and its effectiveness in the separation of close boiling point mixtures led to the growing interest in separation studies of deep eutectic solvents (DESs). DES have advantages over conventional solvents because of its distinctive properties such as thermal stability, easy and inexpensive methods to synthesise, low toxicity levels and biodegradability. DESs are recognized as possible alternatives to ionic liquids for diverse applications in the chemical industry for example in product development. The understanding of physical properties and intermolecular interactions is crucial for researchers and engineers to design more efficient and environmentally friendly processes for the separation of complex mixtures containing volatile organic solvents. This study focuses on the thermophysical and thermodynamic properties of deep eutectic solvents, categorized as type (III), for extraction or separation purposes. Conventional organic solvents, which are currently utilized in industrial processes for extraction or separation purposes are not environmentally friendly. The DESs were synthesized at 1:3 mole ratio of hydrogen bond acceptor (HBA) and hydrogen bond donor (HBD). The classified type (III) deep eutectic solvents under this study were: • DES1: 1-butyl-3-methylimidazolium chloride + ethylene glycol [BMIM]Cl: EG]. • DES2: 1-butyl-2,3-dimethylimidazolium chloride + ethylene glycol [BDMIM]Cl: EG]. The physical properties namely: densities, 𝜌, speed of sound, 𝑢, and refractive indices, 𝑛𝐷, for the binary mixtures [BMIM]Cl: EG + methanol or ethanol, and [BDMIM]Cl: DEG + acetic acid or propanoic acid were experimentally measured over the entire range of mole fraction, 𝑥𝐷𝐸𝑆 = (0-1) at 𝑇 = (293.15, 298.15, 303.15, 308.15, and 313.15) K and at atmospheric pressure. The measurements were conducted using an Anton Paar DSA 5000M and Anton Paar Abbermat 3200 refractometer. From the experimental data, excess thermophysical properties including excess molar volumes, vii 𝑉𝑚 E , isentropic compressibilities, 𝑘𝑠 , change in isentropic compressibilities, ∆𝑘𝑠 , intermolecular free length, 𝐿𝑓, and change in refractive indices, ∆𝑛𝐷, were calculated from the densities, speed of sound and refractive indices, respectively. The investigated properties of the deep eutectic solvent binary mixtures gave an insight into the types of molecular interactions in 1-butylmethylimidazolium chloride + ethylene glycol with methanol or ethanol or 1-butyl-2,3-dimethyl imidazolium chloride + ethylene glycol with acetic acid or propanoic acid at different experimental temperatures. The excess molar volumes, densities and refractive indices data was correlated with the application of the Lorentz-Lorenz equation. Density functional theory (DFT) was used to simulate the intermolecular interaction of deep eutectic [BDMIM]Cl: EG] + acetic acid or propanoic acid as well as [BMIM]Cl: EG] + methanol or ethanol binary mixtures. DFT calculations were employed to ascertain some physiochemical descriptors such as chemical potential (𝜇), electronegativity (𝜒), hardness (𝜂), the global electrophilicity index (𝜔) and softness (𝑆). The activity coefficients at infinite dilution (𝛾13 ∞) of the selected deep eutectic solvents with volatile organic solutes were also determined at different temperatures. The deep eutectic solvents used for the determination of the 𝛾13 ∞ were: • DES3: Tetrabutylammonium acetate with ethylene glycol, [TBN]AcO: EG]. • DES4: Tetrabutylammonium acetate with diethylene glycol [TBN] AcO: DEG] . The activity coefficients at infinite dilution was used as a pre-screening tool for the selection of possible entrainers and was calculated from retention data obtained from gas liquid chromatography (GLC) data. The GLC was operated at the temperature range of 𝑇 = (313.15 – 353.15) K and at 10 K interval. Thermodynamic properties such as excess enthalpies at infinite dilution, ∆𝐻1 E,∞, excess Gibbs free energies at infinite dilution, ∆𝐺1 E,∞, and excess entropy at infinite dilution, ∆𝑆1 E,∞, were computed from the activity coefficient at infinite dilution to further explain the types of intermolecular interactions between the solutes and the investigated DESs. Selectivity at infinite dilution (𝑆𝑖𝑗 ∞), and capacity at infinite dilution (𝑘𝑖𝑗 ∞) values were determined to evaluate the separation potential of the DESs. The data obtained from the spectroscopic techniques Fourier transform infrared (FTIR spectroscopy and nuclear magnetic resonance spectroscopy (NMR) were used to validate the formation of DESs and the types of interactions arising between the HBD and HBA. Furthermore, evaluation of thermal stability for the prepared deep eutectic solvents was determined using differential scanning calorimetry (DSC)/ thermogravimetric analysis (TGA)
Development of electrochemical immunosensors for detection of insulin antibodies using Indolepyrazole nanoparticles
(2025-09) Majola, Senzekile; Sabela, Myalowenkosi Innocent; Makhanya, Talent Raymond; Gengan, Robert Moonsamy
Insulin antibodies have shown to be a strong predictor of diabetes development in genetically susceptible individuals and the development of type 1 diabetes is strongly associated to the presence of antibodies that attack beta cells (islet cells), such as insulin. The development of a sensitive, selective, efficient, and economical insulin detection system is crucial for the diagnosis and management of diabetes. The existing methods can produce results that are very specific, highly sensitive, and dependable. They include notable disadvantages, including high costs, extensive time requirements, the necessity for substantial sample preparation, and the emission of hazardous radiation. Electrochemical assays, characterised by their high sensitivity and selectivity, rapid reaction time, straightforward automation, dependable results, and relatively low cost, can address the drawbacks of conventional approaches. Furthermore, electrochemical sensors utilising biosensor technology provide the most efficacious approach for the detection of antibodies to antigens. Electrochemical immunosensors have emerged as powerful tools for the rapid and sensitive detection of biomarkers. The detection of insulin antibodies is critical for the management of autoimmune responses in diabetic patients. This study aimed to develop and optimise an electrochemical immunosensors for the detection of insulin antibodies using indole-pyrazole capped cobalt or gold nanoparticles. Nanoparticles (cobalt or gold) capped with novel indole-pyrazole derivatives (bis indole-pyrazole or chromone indole-pyrazole) were synthesised and immobilised onto the surface of a bare platinum electrode. Indole-pyrazole derivatives were selected due to their electron-rich, conjugated structures and potential to enhance charge transfer and sensor sensitivity. This modification enhanced the specific surface area and stability of the sensor platform. Insulin antigen was then introduced to promote antibody binding, followed by blocking with bovine serum albumin (BSA) to prevent non-specific binding and improve the accuracy, sensitivity, and reliability of the immunosensor. Each metal nanoparticle had two sensors: one capped with bis indole-pyrazole and the other with chromone-indole-pyrazole. All sensors demonstrated high detection ability for insulin antibodies, with a low detection limit, good selectivity, sufficient stability, and excellent recovery rates. This demonstrates the potential of the developed immunosensors for quantifying insulin antibodies. However, sensors incorporating the chromone-indole-pyrazole derivative outperformed those with the bis indole-pyrazole derivative, exhibiting lower limits of detection (LODs) and higher recovery rates for both metals. The green synthesis of cobalt and gold nanoparticles (CoNPs and AuNPs) using lemon peel extract was successfully achieved, with indole-pyrazole derivatives (BIP and CIP) acting as additional capping agents. Phytochemical screening was conducted to identify the compounds in the lemon peel extract, such as phenols, flavonoids, tannins, and alkaloids, which played a role in nanoparticle stabilisation and reduction. Characterisation techniques such as UV-Vis, FTIR, SEM, and EDS confirmed the successful formation of CoNPs and AuNPs with well-defined morphological and elemental properties. The UV-Vis spectra displayed characteristic surface plasmon resonance peaks, indicating nanoparticle formation. SEM analysis showed that the nanoparticles were predominantly spherical, with some aggregation due to phytochemical interactions. EDS data further confirmed the elemental composition, demonstrating the presence of cobalt and gold within the nanoparticles The fused indole-pyrazole derivatives viz bis indole-pyrazole 4a (BIP) and chromone indole-pyrazole 4b (CIP) were synthesised by reacting aldehyde derivatives, thiosemicarbizide and an indole through a one-pot synthesis via 2+3 annulation. Then, characterised using fourier transform infrared (FTIR), nuclear magnetic resonance (NMR), and time-of-flight mass spectrometry (TOF-MS). To better understand their properties since they are newly synthesised compounds, biological evaluations were performed. Initially, a mutagenicity test was performed, and the compounds showed no significant increase in revertant colonies against S. typhimurium TA 98 and TA 100 strains. In the MTT assay for cytotoxicity against two human cancer cell lines, A549 and HepG-2; and one normal, HEK 293. Compound 4b showed high potency against the cancer cell lines, with IC50 values of 18.70 and 50.07 μg/mL, respectively. Whilst, both compounds showed low inhibition level against HEK 293 at 100 μg/mL. The in vitro inhibition of α-amylase and α-glucosidase, compound 4a demonstrated excellent in vitro inhibition of α-amylase and α-glucosidase, with the IC50 values of 3.9 μg/mL and 12.1 μg/mL, respectively. Compound 4a exhibited strong inhibitory activity against α-amylase and α-glucosidase, for the anticancer activity only compound 4b showed promising results.
Development of high surface area attrition-resistant spray-dried iron catalysts for Fischer-Tropsch Synthesis
(2025-09) Buthelezi, Amanda Samora; Ntola, P; Herees, H J; Tucker, C L
Iron is used as catalyst in the industrial process Fischer-Tropsch Synthesis (F-TS), which is a catalytic chemical reaction that transforms synthesis gas (CO + H2) to create paraffins and olefins for fuels and chemicals. This study aimed to design iron catalysts with a high surface area and attrition resistance for F-TS. The following catalysts: α-Fe2O3, K/Cu/Fe and 0.367 M K/Cu/Fe spray-dried at 200 °C were prepared using the co-precipitation, impregnation and spray-drying methods. The catalysts were then characterized using various characterization techniques including thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) analysis, scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray fluorescence (XRF). Attrition resistance comprised physical tests with the accredited standard method of testing materials (ASTM). The results showed that the 0.367 M K/Cu/Fe spray-dried at 200 °C catalyst has a large surface area of 39 m2 /g and this could be attributed to the small particle size and the catalyst being obtained in a powder form. The α- Fe2O3 catalyst was found to have more physical attrition resistance with a value of 2.2 wt%/h. This was attributed to the small fines produced during the physical attrition test, meaning that the catalyst has a high mechanical strength as compared to other catalysts. The α-Fe2O3 catalyst was also found to have more chemical attrition resistance. This was attributed to the minimum phase change that occurred during the reduction or activation with CO as compared to other catalysts. All the catalysts including α-Fe2O3, K/Cu/Fe and 0.367 M K/Cu/Fe spray-dried at 200 °C demonstrated good selectivity characteristics (low methane and high C5+) hydrocarbons.This was ascribed to the iron carbide (χ‐Fe5C2) active phase or site, which increased the chain growth and favoured the production of C5+ hydrocarbons while decreasing methane selectivity. The α-Fe2O3 catalyst showed high activity and stability, as there was minimal loss of catalytic activity as compared to other catalysts. This was as a result of less CO2 selectivity produced by the catalyst, meaning that there was low water-gas shift activity (WGS) and the active sites were less affected by the presence of water, which causes high loss of catalytic activity. The activity and selectivity of the catalysts need to be improved before the industrial application.
Profiling of selected filamentous actinomycetes isolated from activated sludge plants
(2025-09) Marrengane, Zinhle Gugulethu; Bux, Faizal; Pillai, Sheena Kumari Kuttan; Awolusi, Oluyemi Olatunji
The formation of stable foams on the surface of aeration tanks has been observed worldwide in activated sludge systems. As a result of foam formation, wastewater treatment works face operational difficulties since foam seeps into effluent, adversely affecting the concentration of suspended solids, which reduces disinfection efficiency. Several efforts have been channeled towards a better comprehension of the microbial ecology of foaming. High abundance of Candidatus Microthrix parvicella and branched filaments of mycolic acid-containing actinomycetes have been reported frequently in foaming samples. The proliferation of these microorganisms has been reported from domestic to industrial treatment plants with different process configurations and throughout the different seasons. For process optimisation and troubleshooting, a greater comprehension of the structure and function of microbial community within a wastewater treatment plant is a prerequisite. Excessive growth of filamentous bacteria is promoted by the presence of a variety of physicochemical factors, and changes in process conditions. Though various factors can induce foaming, it is imperative to identify and quantify the indigenous organisms implicated in foaming to pre-empt forthcoming episodes. To date, no metagenomics data have been generated specifically from foaming samples in South African wastewater treatment works. Additionally, the fastidious nature of filamentous bacteria has limited our knowledge of pure culture studies, globally. Almost all of the available literature on pure culture studies in South Africa is more than a decade old and used conventional methods for isolation and purification. Therefore, this study aimed to profile microbial communities that are prevalent in foam samples in selected wastewater treatment works in KwaZulu Natal using a metagenomics approach. Additionally, the study explored the use of micromanipulation techniques for the isolation and cultivation of selected actinomycetes (Gordonia spp.) from foam samples. Two wastewater treatment works treating domestic and industrial wastewater were selected for the study. Microscopic examination of foam samples using wet mount technique indicated the prevalence of right-angled branched filamentous actinomycetes in both wastewater treatment works. The branched filamentous bacteria were selectively isolated using the micromanipulation technique from pre-treated mixed liquor and foam samples. Among the filamentous morphotypes that predominated in mixed liquor were Eikelboom Type 0041, Thiothrix, Gordonia spp., Eikelboom Type 021N and Eikelboom Type 0092 dominated in wastewater treatment works A and in wastewater treatment works B, Eikelboom Type 0041, Eikelboom Type 021N and Gordonia spp. dominated throughout the sampling period while Eikelboom Type 1851 and Thiothrix spp. were identified as transients. A total of forty-four isolates were obtained from the two wastewater treatment works using the micromanipulation technique. Out of these, nine isolates were further selected for physiological and molecular characterisation. The media that supported most isolates was Reasoner’s 2A agar and casitone glucose yeast agar during initial isolation stage. Upon continuous subculturing during preservation, filamentous morphology was permanently lost as the isolate from wastewater treatment works B shifted to single-celled morphology. The selected isolates were further grown in different media containing various carbon substrates such as cholesterol, benzoic acid, glucose, galactose and glycerol and were grown both aerobically and anaerobically. Aerodynamism varied amongst isolates, some displayed no growth under anaerobic conditions whilst only one isolate from wastewater treatment works B utilised all substrates aerobically and anaerobically. Isolates grew optimally at 30o C. Isolates from wastewater treatment works A mixed liquor and foam were fastidious and did not survive the process of isolation and profiling. Phylogenetic analysis of the 16S rRNA sequences indicated that the isolates were close relatives of Gordonia spp. However, the similarity index was lower than 97% indicating that the isolates may be novel or represent divergent variants to existing Gordonia spp. Additionally, quantitative polymerase chain reaction was performed to assess the dominance of selected actinomycetes in foaming samples. Gordonia spp. were successfully quantified and their abundance was related to selected plant operation parameters to establish trends that induce Gordonia spp. proliferation. The ambient temperature of the two respective plants, wastewater treatment works A and B was (24.8 ±5.5 and 28.0o C ± 5.1 respectively) observed to favour the growth of mycolic acid containing actinomycetes. The amount of Gordonia spp. in foams was significantly higher in foam samples than mixed liquor in both the plants investigated. It was also observed that Gordonia copy numbers of 3.7 X 109 ± 0.1 copies/ng were sufficient to induce foaming in these plants. Furthermore, the application of next generation sequencing provided further insight into the role of other actinomycetes in foam formation in this study. Three mixed liquor samples and three foam samples were subjected to next generation sequencing from each wastewater treatment works. Based on the next generation sequencing approach, the microbial community did not vary significantly in mixed liquor and foam, however, abundance changed significantly amongst mycolic acid containing Actinobacteria. An average increase of 17% was observed from Nocardiaceae, Mycobacteriaceae and Gordoniaceae in foams than in mixed liquor. The dominant foam formers in both the wastewater treatment were Gordonia spp., Rhodococcus spp. and Mycobacterium spp. irrespective of the influent characteristics. Gordonia amarae which has been implicated and greatly studied as a foam inducer were not found to be predominant in these wastewater treatment works highlighting the contribution of other potential Gordonia spp. (Gordonia alkanivorans, Gordonia insulae, Gordonia phthalatica, Gordonia polyisoprenivorans, Gordonia rubripertincta) in foaming. Mycobacterium doricum and Rhodococcus coprophilus were also detected from foam samples. The abundance of Mycobacterium intracellulare, Mycobacterium africanum and Mycobacterium avium in wastewater treatment works A and B raises serious health implications. M. intracellulare has been implicated in human pulmonary infections even in immunocompetent individuals. The detection of Mycobacterium tuberculosis in foams also raises health concerns considering the prevalence of HIV in South Africa and tuberculosis co-infections that emanate from immunosuppression. The prevalence of mycobacterial pathogens in foams necessitates deeper interrogation to circumvent occupational hazards. By contributing to the current knowledge base, this study has made a significant contribution towards understanding the organisms responsible for foam formation and stabilization in the subtropical region of KwaZulu-Natal.
Potential probiotic properties of lactic acid bacteria isolated from gastrointestinal tracts of broiler chickens
(2025-05) Kokwe, Nwabisa Happiness; Swalaha , Feroz Mahomed; Tshabuse, Freedom
In poultry farming, antibiotics have been widely utilized as growth enhancers to promote intestinal health and reduce mortality in livestock from pathogenic microorganisms. Many countries have implemented bans on the excessive use of antibiotics because of increasing concerns regarding the resistance of bacteria to antibiotics and the presence of antibiotic residues in poultry products. To counteract this problem, probiotics could be used as adjuncts or as substitutes for preserving a diverse and balanced microflora to prevent the colonization and multiplication of pathogenic bacteria in the gastrointestinal (GI) tract, while also improving poultry performance. The functional properties of lactic acid bacteria (LAB) and their potential as poultry probiotics have been extensively recorded. Hence, this study aimed to assess the potential probiotic properties of LAB for the development of poultry probiotics by isolating lactic acid bacteria from the digestive tracts of broiler chickens. To achieve this aim, a total of 66 LAB isolates were isolated from the crops and small intestines of broiler chickens, which were screened and evaluated for their probiotic properties, among which 11 strains exhibited excellent probiotic traits and were identified by 16S rDNA sequencing as Enterococcus faecalis strain ATCC 19433 (isolates C4 and C5), Pediococcus pentosaceus strain DSM 20336 (isolates C7, C13 C24, SI23 and SI38), Streptococcus salivarius strain ATCC 7073 (isolate SI4) and Levilactobacillus brevis ATCC 14869 (isolates SI6, SI8 and SI9). The selected strains inhibited tested pathogenic bacterial growth Listeria monocytogenes (ATCC 7644), Salmonella enterica (ATCC 13314), Pseudomonas aeruginosa (ATCC 27853) and Staphylococcus aureus (ATCC 29213) with zones of inhibition ranging from 9.00 ±5.66 to 30.00 ±0 mm and survived in simulated gastric juice with a cell viability count greater than 7.0 CFU/ml. Furthermore, the isolates demonstrated remarkable auto aggregation and coaggregation capabilities, along with α-glucosidase inhibitory activity ranging from 25.84 ± 3.08% to 61.77 ± 6.16%. Principal component analysis results indicated that L. brevis NKFS9, P. pentosaceus NKFS3, P. pentosaceus NKFS11 and E. faecalis NKFS1 are the most promising LAB candidates that can be utilized for the development of a multi probiotic strain for broiler chickens. In conclusion, the lactic acid bacteria (LAB) strains isolated from the crops and small intestines of broiler chickens present a valuable prospect for the development of effective probiotics. These probiotics can be utilized as a supplementary inclusion in poultry feed, reducing or obviating the need for antibiotics as growth promoters. Nevertheless, additional in vivo studies are essential to closely monitor and assess the beneficial effects of probiotics on the GI tract of chickens.
Nutritional quality of amadumbe (Colocasia esculenta L. Schott) and development of an efficient tissue culture propagation protocol
(2025-05) Beato, Zwelonke; Amonsou, Eric Oscar; Gitonga, Lucy; Reddy, Viloshanie
Colocasia esculenta (L.) Schott commonly known as amadumbe in South Africa is a conventional underutilised crop. Nutritionally, amadumbe leaves and corms contain nutritionally rich micro- and macro minerals. Amadumbe also contains high fibre, carbohydrates, and protein reserves. Amadumbe can be used as a dual-purpose crop to satisfy undernourished individuals and to alleviate global food insecurity. This research aimed to investigate the quality of amadumbe for use as a green leafy vegetable and to optimize a decontamination procedure to eliminate surface and endogenous contaminants in explants for plant tissue culture. Two sites Umbumbulu (South) and Snembe (North) of KwaZulu-Natal, South Africa were sampled and studied. The two sites are located on opposite ends of the province experiencing varied weather patterns viz. temperature and precipitation. Umbumbulu experiences temperatures of 26.2±20.6°C with annual precipitation of 573 mm compared to Snembe with temperatures of 26.5±20.2°C and annual precipitation of 597 mm. Specifically, the (young and mature) leaves and corms were harvested and processed for the quantification of the nutritional (micro and macro nutrients), proximate composition (organic molecules), antinutritional (oxalate concentrations) and optimisation of plant tissue culture decontamination procedure. Furthermore, soil samples were collected from both sites for determination of the soil mineral composition. Potassium was the dominant macro element ranging from (2.0 – 5.1 g/100 g), calcium (0.08 – 1.5 g/100 g), magnesium (0.14 – 0.48 g/100 g), and phosphorus (0.14 – 0.43 g/100 g) in plant tissues. Furthermore, higher levels of micro nutrients were observed with iron (13.4 -88 mg/100 g) and manganese (2.2 – 64 mg/100 g) dominating. Amadumbe leaves also showed to be abundant in moisture, protein, ash, NDF, and ADF. The soil mineral concentrations were significantly different (p<0.05) between locations with soil:plant organ interaction. The effect of [Control, PPMTM, PPMTM (P), NaDCC, and NaDCC (P)] in eliminating contaminants was insignificant (p>0.05), and further optimization approaches need to be investigated. Benlate, alcohol, and TWEEN 20 did not provide any effective outcome to remove possible endogenous and surface contaminants. Bacterial (BC), fungal (FC), and aseptic (ACS) cultures were lost at 120 d due to obstinate microorganisms.
Survival of waterborne enteric viruses in the Msunduzi River in Pietermaritzburg
(2025-05) Moodley, Justine Olivia; Swalaha, Feroz Mahomed; Pillai, Sheena Kumari Kuttan
Waterborne enteric viruses are ubiquitous in a riverine environment. However, there has been no direct correlation between bacterial faecal indicators and viral contamination in water. Therefore, a viral indicator or combination of bacterial and viral indicators may be necessary to determine contamination in environmental waters and their sources. Enteric viruses are detected in water using various methods including qPCR, RT-PCR, cell culture and sequencing. In this study, adenovirus, norovirus GI and GII, rotavirus A and hepatitis A were detected in all samples collected from the Msunduzi River in Pietermaritzburg using a digital PCR method. Results obtained indicated that environmental factors, including ammonia, temperature, pH, phosphates, rainfall, suspended solids, turbidity and TOC, were found to affect enteric virus survival in a riverine environment. It was further observed that anthropogenic activities such as the Dusi Canoe Marathon impacted the distribution of enteric viruses throughout the Msunduzi River. Adenovirus 40 and 41 and all serotypes were detected together with other enteric viruses and bacterial indicators proving to be a possible indicator for viral pathogens. Little to no correlation was found between enteric viral pathogens and enteric microbial loads in this river. Future work should include the investigation of other possible viral indicators and forming an indicator complex that includes both bacterial and viral indicators for water quality based microbial risk assessment framework.
Cheminformatics bioprospection and experimental validation of corn silk for interventive type 2 diabetes therapeutics
(2025-05) Akoonjee, Ayesha; Sabiu, Saheed
Diabetes mellitus (DM) is one of the oldest known human diseases, with type 2 diabetes mellitus (T2DM) being the most prevalent form. Type 2 diabetes mellitus (T2DM) is characterized by elevated blood glucose levels due to defective insulin production and/or resistance to insulin. If left untreated, it can lead to severe complications affecting various body systems. While synthetic medications are commonly used to treat T2DM, their associated drawbacks, such as high cost, inaccessibility and side effects, mitigate their application in managing T2DM. Consequently, there has been a growing interest in natural products with antidiabetic potential. Natural products, including medicinal plants and plantderived products, have been used for centuries, and their active compounds continue to be explored for therapeutic applications. For example, corn silk (CS), a waste material of corn cultivation, possesses several therapeutic properties, including antidiabetic potential. Although, studies reporting the promising hypoglycaemic potentials of CS exist, its exact mechanism of action remains incompletely elucidated, a research gap that was fulfilled in this study through metabolomics, cheminformatics bioprospection and in vitro experimental validation. To identify the constituents in CS, ultra-performance liquid chromatography-mass spectrometry analysis and principal component analysis was performed on its three extracts (aqueous, hydro-ethanolic and ethanolic) at two developmental growth stages (premature and mature). A library consisting of 128 metabolites was generated from all the samples of CS with qualitative and quantitative variations observed between the two growth stages of CS and the type of solvent used for extraction. Specifically, the mature CS had a higher abundance of most metabolites, with the hydro-ethanolic extract of CS being the most metabolites-rich compared to the aqueous and ethanolic extracts of CS. These metabolites were thereafter subjected to bioprospection against the therapeutic targets, such as enzymes and genes implicated in the pathogenesis of T2DM using computational techniques. The modulatory role of CS metabolites on six enzymes implicated in the pathogenesis of T2DM and its secondary complication, particularly alpha-amylase (AA), alpha-glucosidase (AG), aldose reductase (AR), dipeptidyl peptidase-4 (DPP-4), protein tyrosine phosphatase 1B (PTP1B) and sorbitol dehydrogenase (SDH), was analysed using molecular docking complemented with molecular dynamics (MD) simulation. Molecular docking analysis identified aesculin (-8.1 kcal/mol), austricin (-7.8 kcal/mol), (6E)-1-(4-hydroxyphenyl)-7- phenylhepta-4,6-dien-3-one (-9.9 kcal/mol), (-)-11-hydroxy-9,10-dihydrojasmonic acid 11-beta-D-glucoside (-8.6 kcal/mol), phaseic acid (-6.0 kcal/mol), and erythronolide B (- 9.2 kcal/mol) as compounds with the most negative scores against AA, AG, AR, DPP-4, PTP1B and SDH, respectively. However, a further insight into the binding free energy (ΔGbind) calculations of the putative leads against each enzyme over a 150-ns simulation period revealed that R-7-butyl-6,8-dihydroxy-3-[(3e)-pent-3-en-1-yl]-3,4- dihydroisochromen-1-one (BHP), 1-O-vanilloyl-beta-D-glucose (VBJ), (-)-11-hydroxy9,10-dihydrojasmonic acid 11-beta-D-glucoside (HDJ), p-coumaroyl malic acid (CMA), 2- hydroxydecanedioic acid (HDA), and (-)-11-hydroxy-9,10-dihydrojasmonic acid 11-beta-D-glucoside (HDJ) hold remarkable therapeutic promise as modulators of AA, AG, AR, DPP-4, PTP1B, and SDH, respectively. The post-MD dynamic simulation analysis and interaction plots in each case revealed the formation of thermodynamically stable complexes suggestive of the putative leads as potential modulators of the respective investigated enzymes and their possible applications in the management of T2DM and its secondary complications. Density functional theory (DFT) analysis was used to determine the molecular characteristics of the top ranked CS metabolites identified to modulate the investigated enzyme targets. Although the lower energy gaps, higher softness and lower chemical hardness of the metabolites did not correlate with their high negative binding free energy (potentially due to the observed relative residue fluctuations and increased surface area of the targets upon ligand binding), their electrophilicity indices which were above 1.5 electron volt (eV) alluded to their strong electrophilic potential. This highlights their ability to interact with amino acids with nucleophilic side chains of the target enzymes that is indicative of enhanced specificity and binding to the enzymes. Subsequently, a network pharmacology study was conducted to elucidate the relationship between CS constituents and signaling pathways implicated in T2DM. The analysis identified the cAMP pathway as the central signaling pathway, with adenosine receptor A1 (ADORA1), hydroxycarboxylic acid receptor 2 (HCAR2) and gamma-aminobutyric acid type B subunit 1 (GABBR1) as key therapeutic targets. Gallicynoic acid (-48.74 kcal/mol), dodecanedioc acid (-34.53 kcal/mol), and tetradecanedioc acid (-36.80 kcal/mol) interacted effectively with ADORA1, HCAR2, and GABBR1, respectively, relative to the reference standards (metformin and resveratrol) and formed thermodynamically stable complexes, as indicated by post-MD analysis results. These findings suggest the compounds as potential drug candidates for T2DM through modulation of cAMP pathway genes. The cAMP pathway is implicated in the pathogenesis of T2DM through various levels including glucagon and epinephrine-stimulated cAMP production, increased glucose release from the liver, modulation of insulin signaling, insulin resistance and the regulation of gut hormone secretion, including glucagon-like peptide-1. To complement and validate the results obtained through network pharmacology as a further way of elucidating the mechanism of antidiabetic action of CS, experimental validation employing the use of HepG2 cells was performed. The effect of different CS formulations on HepG2 cells was firstly assessed using the 3-(4,5-dimethylthiazol-2-yl)- 2,5-diphenyltetrazolium bromide (MTT) viability and glucose consumption assays, followed by real-time polymerase chain reaction (RT-qPCR) to understand the effect of CS on the expression of ADORA1 and GABBR1, the top two target genes modulated by the CS metabolites as identified by the network pharmacology study. For the MTT assay, CS extracts at concentrations 75 – 100 µg/mL promoted viability of HepG2 cells, with the ethanolic extract of the mature CS being the most viable relative to the controls (insulinand metformin-treated) and the untreated cells. Generally, higher HepG2 cell viability and glucose uptake were observed following treatment with mature CS extracts compared to premature CS. Specifically, the most significant and enhanced glucose uptake level was observed with both normal and insulin-resistant HepG2 cells following treatment with the aqueous extracts of mature CS extract compared to the controls. Furthermore, compared to the untreated cells, as well as insulin- and metformin-administered cells, treatment with CS extracts remarkably inhibited the expression of ADORA1 and GABBR1 in insulin-resistant HepG2 cells with the most prominent effect observed with the aqueous extract of premature CS. These observation with the CS aqueous extracts may be attributed to their relatively higher abundance of the profiled metabolites such as gallicynoic acid B and tetradecanedioc acid, which were more than 40% each by composition in both the mature and premature extracts. These findings regarding the high concentrations of gallicynoic acid B and tetradecanedioc acid in CS aqueous extracts are not only significant in modulating the expression of ADORA1 and GABBR1, resulting in increased glucose uptake in the treated cells but consistent with the results of MD simulation that profiled the two compounds as putative leads against the two most significant therapeutic targets in the cAMP signalling pathway associated with T2DM. Overall, the findings from this study have contributed to the elucidation of the mechanisms of antidiabetic action of CS metabolites which would be vital in the development of CS as a therapeutic agent for the management of T2DM and its associated secondary complications.
Development of a microalgae-based consortium for the bioremediation of sugar mill effluent
(2025-05) Sibisi, Siphelele; Rawat, Ismail; Bux, Faizal; Mogany, Trisha
Industrial and agricultural activities have increased exponentially to meet the rising demands for food. The sugar production process is water-intensive and requires high volumes of freshwater that are subsequently discharged as effluent. An average of 1000 L of wastewater is produced per ton of sugarcane processed. The sugarcane industry wastewater is characterized by high chemical oxygen demand (COD: 1752 - 8339 mg L-1), and biochemical oxygen demand (BOD:1052 - 4641 mg L-1) but remains low in nutrients and other minerals. Discharging untreated wastewater into the environment might have negative consequences, thus reusing and treating wastewater is essential. Conventional physiochemical treatment methods including sedimentation, filtration, and coagulation-flocculation have shown limited efficacy. The sugar industry wastewater exhibits high biodegradability, thus biological treatment techniques are preferred due to environmental friendliness and sustainability. In recent years, the co-culturing approach has gained interest as a strategy to improve the biotechnological productivity of microalgae in wastewater treatment. This study aims to develop stable microalgae-based consortia using native, microalgal, bacterial and yeast strains. The steps adopted for achieving the above-stated aim were: (1) isolation, identification, and characterization of indigenous microorganisms from wastewater, and (2) assembling microbial consortia to identify the most effective and compatible strains. Indigenous microalgal, bacterial, and yeast strains were isolated and screened for growth in synthetic wastewater. The strains exhibiting significant growth were further characterized in real wastewater from the sugar industry to evaluate their performance efficiency based on COD removal efficiencies. To attain higher wastewater treatment efficiencies, different primary and secondary combinations of consortia were constructed from the pool of previously screened and selected microbial strains guided by the bottom-up approach. The microalgal, bacterial, and yeast microbial strains present in the final consortia were identified using polymerase chain reaction and sequencing. The final microalgal-based consortia were characterised in real effluent to assess wastewater treatment efficiency and elucidate their basic interactions for better application. Two microalgal, seven bacterial, and four yeast strains were isolated from the sugar industry wastewater. In the primary screening procedure in synthetic wastewater, two microalgal strains (A7 and C12), and four bacterial (B003, B009, B010, and B013) strains were found to grow substantially and thus selected for further studies and subsequent microalgae-consortia development. The two microalgal strains showed high removal efficiency for NO3--N (98–100%), NH4+-N (62-65%), and PO43--P (75-80%), however, the removal rate for COD was mainly observed in bacterial strains ranging between 1–73%. Also, the yeast strain (Y2) reduced COD from 22660 to 11690 mg L-1 (48% removal rate) within 168 h of cultivation. The co-culturing of microalgae with bacteria and yeast could improve the treatment of high-strength wastewater. In this regard, four primary, and three secondary consortia were considered. In all the primary consortia (B009A7, B010A7, B013A7, and Y2A7), improvement in removal efficiency for Total Nitrogen (TN) and Total phosphorus (TP) was recorded in ranges between 75-80% and 84-94%, respectively. However, a significantly lower removal rate (4-7%) was observed for COD. Furthermore, three secondary (B009B010A7, B009B013A7, and B010B013A7) and one tertiary consortia (B009B010B013A7) were considered. All secondary consortia exhibited a prolonged lag phase with reduced COD removal efficiency. In contrast, the tertiary consortia showed improved COD, TN, and TP removal efficiency corresponding to 26%, 85% & 73% (respectively) in synthetic wastewater. The microalgal, bacterial, and yeast strains in the final consortia were identified as Chlorella sorokiniana A7, Rhodococcus sp B009, Bacillus sp B010, Bacillus sp B013, and Saccharomyces cerevisiae Y2. The wastewater treatment efficiency of the consortia (MBC and MYC) was further evaluated in real sugar industry wastewater. The COD removal efficiency was found to be 86% and 71% after 4 days of cultivation for MBC and MYC, respectively. In addition, the co-culture with S. cerevisiae Y2 markedly increased chlorophyll-a content, photosynthesis, and respiration in microalgae. The microalgal-based consortia exhibited physical and biochemical interactions, with improved yield parameters and metabolite production between microalgae, bacteria, and yeast. The co-cultivation of Chlorella sorokiniana A7 and Saccharomyces cerevisiae Y2 was observed to have the highest COD removal efficiency from wastewater (100% within 4 d of cultivation). Microalgae and yeast mutually benefited from each other in the MYC system with synergistic cross-feeding between specific parameters such as CO2/O2, and organic acids. In addition, indole-3-acetic acid (IAA) was selected as a marker for evaluating the plant growth-promoting effects of co-cultured partners and determining the communication intensity. All co-cultured strains were found to produce and secrete indole acetic acid (IAA), suggesting plant growth-promoting effects. All the co-culture partners produced different concentrations of IAA under tryptophan ranging between 2 to 129 mg L-1. Meanwhile, IAA production was highest within 24 hr of cultivation in the MBC system, while the MYC exhibited a steady increase in IAA production, with the highest production observed after 72 h. The IAA signals are suggested to facilitate the establishment of mutualistic associations between microalgae and yeast/bacteria under varying environmental conditions. This indicates that yeast/bacteria may promote the growth of the co-existing microalgae through secretion of IAA, and microalgae would selectively enhance IAA secretion, thus, shaping the physiology and ecology of the partners in the microbial consortia. The study demonstrated the efficacy of microalgae-based consortia that have potential use in treating high-strength COD wastewater. The results could help improve the performance of the current treatment methods by introducing low-cost and sustainable biological technologies. The study demonstrated that microalgal-based co-cltivation is a promising bioremediation tool for high-strength biodegradable wastewater and presents environmental value in the design of low-energy, small-scale biological treatment systems. An insight into mechanisms of interactions between microalgae and co-cultured microbes still requires further study through integrated omics, studying the ecology and diversity of microbial communities could improve their application in environmental monitoring and bioremediation.
Metabolomic profiling, computational and experimental validation of sunflower seeds as therapeutics against type-2diabetes mellitus
(2025-05) Rampadarath, Athika; Sabiu, Saheed; Makunga, Nokwanda
Type 2 diabetes mellitus (T2DM) is a chronic metabolic disorder characterized by impaired glucose metabolism due to insufficient insulin secretion or insulin resistance. This global health crisis is projected to affect an estimated 7079 individuals per 100,000 by 2030. While medications like metformin are effective, accessibility and affordability are issues consistent with low-income populations alongside potential side effects like hypoglycaemia, nausea and gastrointestinal issues that have limited their use in clinical practice. More importantly, uncontrolled T2DM can lead to serious complications like retinopathy, nephropathy, neuropathy, and delayed wound healing. Therefore, this prompts the search for alternative management options that are safer, easily accessible, affordable and with minimal side effects. Plants and their products are becoming increasingly important due to their relative ease of accessibility, affordability and potential health benefits. Sunflower seed, a popular dietary snack, has rich nutritional profile and has found significant health benefits as an antiinflammatory, antioxidant, anticancer, antimicrobial, and antidiabetic agent. While the antidiabetic potential of sunflower seeds has been explored, there remains a lack of understanding on its mechanism of action. This study addressed this knowledge gap by establishing the comprehensive metabolite profiles and investigating the antidiabetic efficacy of sunflower seed extracts through a two-pronged approach: targeted enzyme inhibition and network pharmacology analyses complemented with experimental validation in vitro. Metabolomic profiling of six cultivars of sunflower seeds commonly consumed in South Africa, namely, AGSUN 8251, 5270, 5101 CLP, 5103 CLP, 5106 CLP and 5108 CLP was performed using Liquid chromatography – mass spectrometry (LC-MS) and Gas chromatography – mass spectrometry (GC-MS) techniques. A total of 94 metabolites were identified, with LC-MS analysis revealing 44 phenolic compounds across the six cultivars with a minor variance of 39.7%, while GC-MS analysis revealed the presence of volatile compounds such as organic acids, alkanes, alcohols, terpenes, heterocyclic compounds and hydrocarbons in all the cultivars in similar abundance. Noteworthily, 84 of the 94 metabolites profiled passed Lipinski’s rule of five and were selected for further analysis. For the enzyme inhibition study, molecular docking analysis was initially used to screen the profiled metabolites against the key enzymes [α-amylase (AAMY), α-glucosidase (AGLU), aldose reductase (AR), sorbitol dehydrogenase (SDH), dipeptidyl peptidase 4 (DPP-4) and protein tyrosine phosphatase 1B (PTP1B)] implicated in T2DM pathogenesis and its secondary complications. The top-ranked metabolites against each enzyme were further subjected to molecular dynamics (MD) simulation to identify putative leads with the strongest binding affinity, and unperturbed structural integrity through evaluation of their stability, compactness and intermolecular interactions. This aspect of the study identified sonchuside I (SON I) - AAMY (–47.26 kcal/mol), sacranoside A (SAC A) - α-glucosidase (–40.10 kcal/mol), pelatoside A (PLT) - AR (–58.84 kcal/mol), sacranoside A (SAC A) - SDH (–48.03 kcal/mol), 4α,6S,7α)-6α-[6-O-(4-Hydroxybenzoyl)-β-D-glucopyranosyloxy]-7βmethyloctahydrocyclopenta[c]pyran-1-one) (PYR) -DPP-4 (–37.93 kcal/mol) and chlorogenic acid (CGA)-PTP1B (–24.32 kcal/mol) as potential lead inhibitors of the respective enzyme relative to their respective reference standards. This was further supported by their improved thermodynamic properties and favourable post-dynamic simulation parameters such as improved stability and compactness of their resulting complexes. These observations are suggestive of multiple mechanisms by which sunflower seed may exert its antidiabetic effects such as anti-hyperglycaemia (α-amylase and α-glucosidase), prevention and management of diabetic complications (AR and SDH), increasing insulin signalling (DPP-4) and sensitivity (PTP1B) by the respective putative leads. For network pharmacology analysis, the filtered sunflower seed metabolites were used to create a gene-compound library that was subsequently used to identify genes commonly associated with both the metabolites and T2DM. Thereafter, Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathway enrichment analysis was performed to identify the most significantly enriched pathways with key target genes for molecular docking and MD simulations to identify lead metabolites. Finally, the antidiabetic activity of sunflower seed extracts and the findings from the network pharmacology analysis were validated using insulin-resistant HepG2 cells where glucose consumption assay and gene expression analysis were performed. The network pharmacology analysis revealed a total of 87 genes common to sunflower seeds metabolites and T2DM, whereas KEGG enrichment analysis highlighted 35 signalling pathways potentially influenced by the metabolites. Of these, the Peroxisome proliferator-activated receptor (PPAR) signalling pathway and its hub receptors, Matrix metalloproteinase-1(MMPI) and peroxisome proliferator-activated receptor alpha (PPAR) were selected as the most significant. These receptors interacted mostly with the identified metabolites, with CGA (– 43.74 kcal/mol), GPA (–41.62 kcal/mol), and CFG (–45.36 kcal/mol) having lower binding free energy than both reference standards, rosiglitazone (ROS) and metformin (MET) against MMP1 after 100 000 ps MD simulation. In contrast, ROS (–46.98 kcal/mol) had better affinity against PPARA compared to the top-hits derived from sunflower seeds. However, against both genes, the top-hits had significant thermodynamic stability, flexibility, and compactness, which are attributable to their bond interactions and molecular orbital properties. These findings are suggestive of the essential role of the top-hits in the antidiabetic potential of sunflower seeds through activation of the PPAR signalling pathway and most especially MMP1. In this regard, the modulation of MMP1 and PPARA genes by the identified metabolites of sunflower seeds may enhance insulin sensitivity and glucose homeostasis in the management of T2DM. Finally, the in vitro validation using insulin-resistant HepG2 cells revealed cultivar-specific effects on cell viability, with each cultivar having a unique optimal concentration. Overall, all cultivars demonstrated the ability to stimulate glucose consumption, suggesting their potential antihyperglycemic activity. Among the cultivars, AGSUN 5103 CLP (14.4 mmol/L), 8251 (14.6 mmol/L), and 5101 CLP (13.7 mmol/L) exhibited the most pronounced glucose lowering action compared to the untreated cells (23.3 mmol/L) after 24 h, highlighting their promising antidiabetic effects. These three cultivars also modulate the PPAR signalling pathway, as evidenced by the upregulation of MMP1 and PPARA expression. Specifically, AGSUN 5101 CLP emerged as a particularly promising candidate based on its superior glucose lowering potential and higher fold increase expression of MMP1 (1.88) and PPARA (4.59) compared to the effect observed with the untreated cells (1.00). In conclusion, this study provides compelling evidence for the antidiabetic potential of sunflower seeds. The observed effects on enzyme inhibition, activation of the PPAR signalling pathway, and stimulation of glucose uptake in HepG2 cells suggest a multifaceted approach by the seeds in regulating blood sugar levels. The identification of cultivar-specific effects and promising lead compounds warrants further investigation to explore the therapeutic potential of sunflower seeds in managing T2DM.
Application of cold plasma for inactivation of waterborne pathogens
(2025-05) Rampersad, Amelia; Swalaha, Feroz Mahomed; Reddy, Kevin P.
The inactivation of harmful pathogenic microorganisms during water treatment is essential for ensuring safe and clean water for human consumption. Current treatment technologies exhibit limitations in effectively eliminating pathogenic contaminants, necessitating the exploration of advanced disinfection technologies. This study investigates the application of atmospheric cold plasma (ACP) as a novel disinfection method for water contaminated with various pathogens, optimising key treatment parameters such as electrode distance and gas type (oxygen, argon and air) at voltages of 9.56 kV- 13.53 kV over treatment durations of 0.5-2.5 minutes. The study assessed ACP’s efficacy against chlorine-resistant and non-chlorineresistant bacteria, examining direct ACP treatment and effects after 24 h storage post-treatment. Bacterial suspensions at initial concentrations of 1 x 107 CFU/mL were exposed to varying treatment conditions, with bacterial inactivation analysed via colony counts and statistical analyses (two-way ANOVA with Tukey’s post-hoc). The results indicated significant log reductions in bacterial populations, with ACP achieving up to 4-log reductions, particularly against chlorine-resistant, Gram-negative bacteria. Among the gases tested, argon plasma had the highest bacterial inactivation rates, outperforming oxygen and air plasma, particularly against chlorine–resistant bacteria. Environmental water samples treated with ACP showed 90-100% bacterial inactivation, corresponding to log reductions of 3-5 logs, consistent across both direct and 24 h storage post-treatment samples. Argon and oxygen plasma showed high efficacy, with oxygen plasma having the highest inactivation in the uMhlanga Lagoon sample. The sustained antibacterial effect of ACP after 24 h storage post-treatment was attributed to its disruption of bacterial cellular functions, effectively inhibiting regrowth and ensuring long-term water safety. These findings confirm the potential of ACP as a highly effective and adaptable disinfection technology for water purification, particularly in targeting bacteria with carrying resistance profiles. While this study highlights the efficacy of ACP in inactivating pathogenic bacteria, further research is needed to ensure the safety of treated water for human consumption and to evaluate its effectiveness in removing chemical contaminants. This study demonstrates that ACP is a highly effective disinfection technology for water treatment, with consistent success in inactivating a wide range of pathogenic bacteria.
Multicomponent synthesis, characterization and antimicrobial evaluation of pyrazole derivatives
(2025-05) Mntambo, Bahle Luyanda Dave-Junior; Makhanya, Talent Raymond; Gengan, Robert Moonsamy
People have been ailing regularly nowadays and conventional antibiotics have become less potent due to drug resistance. The molecular architecture of the antibiotics issued to patients has only marginally changed since their discovery, thus this has caused microorganisms to adapt or survive the repeated administration of the same drugs over time, causing medication to be less effective, and people becoming sicker because the lack of new, different and potent antibiotic structures has enabled bacteria to mutate. This presented the pressing need to develop pyrazole compounds because they suit the category of being structurally different and have been reported to exhibit excellent antibacterial activities. To obtain pyrazole derivatives, Microwave-Assisted Organic Synthesis (MAOS) was utilized to synthesize ten novel compounds of (4Z)-4-arylidene-4,5-dihydro-3-methyl-5-oxopyrazole-1-carbothioamide derivatives (4a-4j) by a one-pot multicomponent reaction (MCR) methodology that is ecofriendly and adhering to green chemistry principles, occurring by catalyst-free in a waterethanol solvent system. The methodology to access novel pyrazoles (4a-4j) in this study is superior to conventional pyrazole synthesis because it requires harsh reaction conditions and expensive catalysts, which deviates from green chemistry. All synthesized compounds (4a-4j) were fully characterized and confirmed by 1H NMR, 13C NMR, 2D NMR, FTIR and TOF-MS. Antimicrobial study was performed against two Gram-negative and two Gram-positive strains viz. Escherichia Coli (E.Coli), Pseudomonas aeruginosa (P. aeruginosa), Staphylococcus Aureus (S. Aureus), and Streptococcus pneumoniae (S. pneumoniae), respectively, and amoxicillin was used as the reference drug. It was found that only 4c and 4j exhibited activity against E. coli and their Minimum Inhibitory Concentration ( MIC) values were 1.38 and 2.50 mg/mL, respectively. In contrast, Amoxicillin displayed a lower MIC value of 0.0306 mg/mL, thereby suggesting that amoxicillin is more effective than the synthesized pyrazoles against E. coli. Pyrazoles 4a, 4d, and 4g showed no antibacterial activity against P. aeruginosa. Compounds 4b, 4c, 4e, 4f, 4h, 4i, and 4j displayed varying MIC values ranging from 0.212 to 0.625 mg/mL against S. aureus, 4i being 0.212 mg/mL the lowest MIC value. Amoxicillin displayed a lower MIC value than all the pyrazoles against P. aeruginosa. Against S. pneumoniae, 4j demonstrated an excellent antibacterial potential with a lower MIC value of 0.0156 mg/mL compared to that of amoxicillin (0.0306 mg/mL). The other pyrazoles displayed marginally higher MIC values than amoxicillin; 4g showed no activity for S. aureus. However, 4i displayed the lowest MIC value, suggesting its potential as an antibacterial agent. It was percieved that the unsubstituted phenyl ring in 4i contributed to its enhanced potency against test bacteria. Molecular docking studies were performed to predict the binding sites and affinities of the pyrazoles, revealing that they primarily target Penicillin Binding Proteins (PBPs) in the test bacteria. Docking scores for E. coli ranged from -6.7 to -7.9 kcal/mol and compound 4f exclusively exhibited the best docking score of -8.1 kcal/mol against E. coli better than amoxicillin’s docked score of -7.0 kcal/mol. Docking scores for P. aeruginosa ranged from - 6.8 to -7.7 kcal/mol. Compounds 4g and 4j displayed the highest negative docking scores of - 7.7 kcal/mol, outperforming amoxicillin thereby suggesting their potential as inhibitors, however 4b and 4f were comparable. Furthermore, in silico simulation, Molecular Dynamics (MD) studies were conducted for 4g and 4j. Docking scores for S. pneumoniae range from - 7.2 to -8.1 kcal/mol. Compound 4j displayed the highest negative docking score. Agreement between docking and in vitro results reinforces 4j as a potential inhibitor. The pyrazoles exhibited docking scores between -5.5 and -6.6 kcal/mol for S. aureus with 4j showing potential as an inhibitor. While lower than other PBPs, some pyrazoles are comparable to amoxicillin. Furthermor, the pyrazoles exhibited LogP (Lipophilicity) values oscillating between 1 and 2.5, indicating better bioavailability. Amoxicillin, partitioned close to an aqueous phase, showed by a negative LogP value of -0.29. Amoxicillin’s LD50 (lethal dose for killing 50% of the bacteria) is 15 g/kg, suggesting non-toxicity orally. Among pyrazoles, only compound 4c shares this safety profile as amoxicillin, qualifying 4c to be an orally administered antibacterial agent. Other pyrazoles fall into toxicity class 4, necessitating alternative administration routes, such as IV (Intravenous) or IM (Intramuscular). All studied compounds showed no affinity for BBB (Blood-Brain Barrier) permeability or P-glycoprotein binding, indicating they can traverse the system without hindrance from nonspecific enzymes or tissues. Compound 4d does not inhibit any CYP (Cytochrome P450) isoenzymes, similar to amoxicillin. Compound 4e selectively inhibits CYP 3A4, relevant for drug metabolism.
Production, characterisation, and application of Beauveria bassiana SAN01 β-glucosidase
(2025-05) Magwaza, Buka Welcome; Pillai, Santhosh Kumar Kuttan; Amobonye, Ayodeji
Beauveria bassiana is a popular entomopathogenic fungal endophyte that is used industrially as a biocontrol agent. It has been noted to be non-pathogenic to humans, animals and plants and their ability to utilise various agro-residues for its metabolism has been exploited for the production of some lignocellulosic enzymes. Previous studies have mostly focused on the production of key lignocellullose hydrolysing enzymes, however, little is known about the ability of B. bassiana to produce accessory enzymes such as β-glucosidase which also aid in lignocellullose breakdown. Hence, this study was aimed at investigating the production, the biochemical characteristics, and the potential application of a β-glucosidase from the strain designated as Beauveria bassiana SAN01. For these aims to be achieved, the production parameters of β-glucosidase were optimised using a statistical approach. Furthermore, to enhance the evaluation of the biochemical properties and potential industrial application of the enzyme, it was purified to homogeneity using salt precipitation, and chromatography. The preliminary screening of seven agricultural residues showed that the haulm of Bambara an underutilised African legume- supported the highest β-glucosidase production, hence, statistical optimisation of enzyme production was performed using this biomass as the sole carbon source. The three-level statistical optimisation experiments resulted in a ~5.36-fold increase in β-glucosidase production from the unoptimised level of 132.71 U/mL to 711 U/mL, under optimal conditions (Bambara - 57 g/L, KCl - 302 mg/L, NaCl -154 mg/L, agitation -150 rpm, and incubation time - 223 h). Ammonium sulphate precipitation followed by dialysis and gel filtration chromatography were used to purify β-glucosidase produced by B. bassiana SAN01 to homogeneity. The purified β-glucosidase was demonstrated to have a specific activity of 496 U/mg and a molecular mass of ~116 kDa by SDS-PAGE; its activity pattern was also confirmed via in-gel zymography using 4-methylumbelliferyl-β-D-glucopyranoside as the substrate. The enzyme activity was recorded to be optimal at pH 5.0 and 60°C and the enzyme also displayed significant thermal stability from temperatures 30-50°C, retaining almost 60% of its activity at 50°C after 4 h of incubation. Subsequently, the potential of B. bassiana SAN01 β-glucosidase as an accessory enzyme in lignocellulose saccharification was demonstrated by its effectiveness in the hydrolysis of cellobiose converting more than 90% of the substrate to glucose. Finally, some structural insights were gained into the enzyme using a computational approach. The in silico prediction of the enzyme revealed that it has an isoelectric point of 5.59, that it was hydrophilic and thermostable. The modelled 3D structure of B. bassiana β-glucosidase confirmed that it belongs to the GH 1 family and the model was validated by the presence of ~ 96% of its amino acid residues in the favoured region of the Ramachandran plot. The docking of the enzyme with cellobiose and 4-nitrophenol β-D glucopyranoside demonstrated the significant affinity of both substrates to the enzyme while revealing its most probable active site. Results from this study demonstrate B. bassiana as a hyper-producer of β-glucosidase as the production level in this study is one of the highest ever recorded for an entomopathogenic fungi; thus the study highlights the immense potential of B. bassiana in the processing of lignocellulosic biomass to biofuels.
Synthesis, assessment, and application of two-dimensional ferromagnetic nanocomposites for the removal of microplastics from drinking water and wastewater effluent
(2025-05) Indhur, Riona; Kumari, Sheena; Kumar, Arvind; Bux, Faizal
The increase in microplastics (MPs) concentration in water matrices continues to pose a serious threat to aquatic ecosystems, and subsequently human health as a result of bioaccumulation within these aquatic organisms. Significant number of MPs have been detected from different water matrices including surface water and wastewater treatment effluent, globally. Recent reports from South Africa have also indicated their presence in tap water in low concentrations. Water treatment plants globally, are not optimised or designed for the removal of MPs. Therefore, technological innovations are required to alleviate the limitations embedded in these treatment systems. Nanotechnology has emerged as a pivotal technology to address a wide range of environmental challenges through performance enhancement. Therefore, this study investigated the removal of MPs from aquatic environments using magnetic nanocomposites (MNCs). This is the first study to the best of our knowledge that explicitly evaluates the performance of MNCs g-C3N4@Fe3O4 and BNNS@Fe3O4 for the removal of MPs. Herein, the application of each MNC is assessed for their removal efficiency of individual and multitudinous combinations of polystyrene (PS) and polyethylene (PE) MPs, including different size ranges. Additionally, these MNCs are applied in drinking water and real domestic wastewater effluent to determine their effectiveness against a combination of PS and PE MPs. Furthermore, a phytotoxicity study was also conducted to assess the toxicity of g-C3N4@Fe3O4 and BNNS@Fe3O4 on various common agricultural crops (Hordeum vulgare L. (barley wheat), Cicer arietinum (black chickpea) and Vigna radiatus L. (moong)). The recyclability study was performed for five successive rounds of reuse and each of the MNCs magnetic stability was assessed via VSM. Finally, a cost assessment analysis for MPs removal with the best performing MNC (g-C3N4@Fe3O4) was also conducted as well as the mechanistic insights of the interactions between PE/PS MPs and the MNC was postulated. The MNCs (g-C3N4@Fe3O4, BNNS@Fe3O4) were synthesized by conventional co precipitation. Synthesized MNCs were characterised by various analytical techniques such as, XRD, TGA, FTIR, BET, XPS, SEM-EDX, TEM, VSM, and Zeta potential. The optimization of various parameters (pH, time, MNC dose, MP dose) were done through gradient experiments. Optimised parameters were applied in batch experiments to investigate g C3N4@Fe3O4 and BNNS@Fe3O4 for the removal of different types and sizes of MPs (PE (125 µM), PS (25-180 µM), PE+PS combo (PE=125 and 25-180 µM) and PS (180-500 µM) from Milli-Q water, wastewater effluent and drinking water. The maximum removal of PE (96.16%, size 125 µM), PS (92.5% , size 25-180 µM), PE+PS combo (94.89%, size PE=125 and 25-180 µM) and PS (45.62%, size 180-500 µM) were noticed with MNC g-C3N4@Fe3O4 under optimum operating conditions ([pH]= 4; time= 5 h; [MNC]= 1.2 g/L; [MP]= 0.5 g/L) from Milli-Q water. The maximum removal efficiency of PE (94.44%, size 125 µM), PS (85.96%, size 25-180 µM), PE+PS combo (88.28%, size PE=125 and 25-180 µM) and PS (38.77%, size 180-500 µM) were observed with MNC BNNS@Fe3O4 under optimum operating conditions ([pH] = 3; time= 12 h; [MNC]= 0.9 g/L; [MP] = 0.5 g/L) from Milli-Q water. A direct correlation was observed between the removal rate and the size of the MPs. The investigation of MNC removal efficiency in different water matrices yielded 93.7 and 86.56% from drinking water via g-C3N4@Fe3O4 and BNNS@Fe3O4, respectively. A removal rate of 91.91 and 83.78% was observed from domestic wastewater effluent filtered with a 0.22 µM filter for g-C3N4@Fe3O4 and BNNS@Fe3O4, respectively, whilst a removal rate of 90.28 and 82.23% was observed from the same domestic wastewater effluent (unfiltered) for g-C3N4@Fe3O4 and BNNS@Fe3O4, respectively. The results for filtered and unfiltered wastewater effluent are similar indicating that filtering plays no significant role in improving the removal efficiency. The reusability study revealed that both MNCs retained a removal efficiency of more than 50% after 5 cycles whilst g-C3N4@Fe3O4 retained a removal efficiency of almost 80% after 3 cycles. The VSM results exhibited that both MNCs possess superparamagnetic behaviour which indicates that both BNNS@Fe3O4 and g-C3N4@Fe3O4 have excellent magnetic properties, enabling their application in practical settings. This was further confirmed by the after-treatment results wherein both MNCs retained their superparamagnetic properties after adsorption of the MPs, allowing for effective magnetic separation. MNCs' phytotoxicity on common agricultural crops was assessed to investigate any potential ecotoxic effects on the crops. The phytotoxicity of domestic raw wastewater influent, final treated effluent, g-C3N4@Fe3O4, BNNS@Fe3O4, g-C3N4@Fe3O4 filtrate and BNNS@Fe3O4 filtrate were assessed through seed germination indices (G.I.%). The MNC filtrate of g C3N4@Fe3O4 and BNNS@Fe3O4 revealed mild toxicity (approaching non-toxic) and no toxicity, respectively. The operating cost of g-C3N4@Fe3O4 for MPs removal from domestic wastewater effluent was approximately 41.09$/m3 . This makes it is a cost-effective treatment when compared to literature. The four main potential interactions postulated to occur between the PS/PE MPs and g-C3N4@Fe3O4 and BNNS@Fe3O4 MNCs are: electrostatic interaction, π π interaction, Van Der Waals forces and hydrogen bonding. In conclusion, this thesis demonstrates the promising potential of MNCs (g-C3N4@Fe3O4 and BNNS@Fe3O4) for the efficient removal of MPs from various water matrices, including drinking water and final treated wastewater effluent. The remarkable removal efficiency and superparamagnetic properties of these materials, coupled with their low environmental toxicity and cost-effectiveness, highlight their feasibility for practical applications. This thesis further confers the understanding of g-C3N4@Fe3O4 and BNNS@Fe3O4 MNCs recyclability, therein promoting a circular economy and a sustainable approach for wastewater treatment. These findings contribute to advancing sustainable wastewater treatment solutions and address the global challenge of MP pollution

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