Theses and dissertations (Applied Sciences)

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Characterisation of gluten-free dough mixes from traditional food crops with reduced starch digestibility for baking applications
(2025) Govender, Samantha; Amonsou, Eric
Gluten-free (GF) baking is challenging because gluten, which is absent, gives wheat-based doughs their elasticity, structure, and ability to retain gas. Developing gluten-free dough mixes requires a strategic selection of substitute ingredients that can mimic gluten's functional properties. This calls for the use of various starches, flours, hydrocolloids, and proteins to achieve desirable dough rheology and final product characteristics. The challenge lies in optimizing the interactions between these ingredients to create a cohesive and elastic dough structure that can withstand processing and deliver acceptable sensory attributes. The choice of suitable ingredients and their proportions is crucial for achieving a balance between dough stability, gas retention, and crumb structure. Therefore, food scientists and technologists find it challenging to create baked foods that are gluten-free. For glutenfree products to be more widely accepted by consumers, these ingredients must ensure that they resemble typical bakery goods as much as possible. Amadumbe, millet, and psyllium offer unique properties that can be harnessed to create gluten-free dough mixes. Amadumbe, a starchy root crop rich in resistant starch, can reduce the glycemic load of baked goods. Millet is a gluten-free grain with high nutritional value, providing vital amino acids, minerals, and antioxidants. Psyllium, a soluble fibre, has been shown to improve dough handling, increase viscosity, and improve the textural properties of gluten-free baked goods. The combination of these ingredients can address the textural and nutritional deficiencies often associated with gluten free products. The focus of this research was the characterization of gluten-free dough mixes with reduced starch digestibility for baking applications. This was done by A; investigating the effect of hydrothermal treatments: annealing (ANN) and heat-moisture treatment (HMT) combined with 3% psyllium husk fibre (PHF), on the structural, rheological, pasting, and digestibility properties of maize starch with varying amylose content. B; evaluation of the functional and digestibility profiles of a gluten-free (GF) premix blend made from amadumbe and millet, supplemented with psyllium fibre, and C; the optimized gluten-free flour blend was tested for its dough-forming ability and baking quality. Hydrothermal treatments: annealing (ANN) and heat-moisture treatment (HMT), combined with 3% psyllium fibre supplementation, significantly (p < 0.05) enhanced the rheological, pasting, and starch digestibility profiles. However, hydrothermal treatment alone caused minimal to no change in these functional properties. The results demonstrated that fibre supplementation of both HMT- and ANNtreated starches increased peak viscosity, trough viscosity, final viscosity, and setback viscosity, with ANN exhibiting significantly higher values. ANN fibre-supplemented normal maize starch showed the largest increase in storage modulus (G'), according to rheological analysis. Profiling of starch digestibility revealed that fibre-supplemented high amylose maize starch produced the greatest levels of resistant starch (RS). These findings highlight the importance of developing healthier starches that promote well-being by reducing digestibility and increasing resistance to enzymatic breakdown. This will support the creation of low-glycemic, fibre-rich products. The results of the investigation proved useful in establishing the criteria for the amadumbe-millet and psyllium flours used to produce glutenfree composite blends. The evaluation of processed gluten-free (GF) flour blends made from amadumbe, millet, and psyllium flours revealed that the inclusion of psyllium fibre significantly improved the pasting properties (PV, FV, BV) two-fold. The rheological properties showed enhanced viscoelasticity of the dough, as indicated by the storage modulus (G') consistently being greater than the loss modulus (G") across the frequency range. Starch structural analysis using X-ray diffraction (XRD) indicated that all blends exhibited a typical A-type crystalline structure. The analysis of starch digestibility showed a significant increase in resistant starch (RS) and a decrease in rapidly digestible starch (RDS) due to the presence of psyllium fibre. Results obtained from this study suggest that fibre-supplemented gluten-free flours have great potential for baking, owing to their improved functional properties and reduced digestibility profile. The optimized gluten-free blend of amadumbe, millet, and psyllium (in a ratio of 70-30-3) was further evaluated for its dough-forming properties by examining water absorption capacity (WAC), oil absorption capacity (OAC), rheological properties, and textural properties. All the tests performed showed improvement with the inclusion of fibre. To assess the baking quality of the bread, textural analysis and sensory evaluation were conducted. Sensory evaluation assessed the amadumbe-milletpsyllium bread (AMP1) with a commercially available gluten-free bread. The results for overall acceptance indicated comparable findings (6.62±1.86) for AMP1 bread and (6.91±1.63) for the commercial gluten-free bread. However, starch digestibility results showed a reduction in resistant starch (RS) content, which was attributed to the increased baking temperature and time. This research contributes to the advancement of gluten-free bread with enhanced nutrition, texture and shelf life, meeting the growing demands of health-conscious consumers and gluten-intolerant individuals. Therefore, this study furnishes valuable insights for food scientists, bakers, and ingredient manufacturers, guiding the preparation of novel gluten-free products with enhanced nutritional and sensory attributes.
Seasonal consumption and contribution of indigenous leafy vegetables to household food security and daily recommended intakes in a rural community in Ndwedwe, KwaZulu-Natal
(2025) Hlekwane, Ayanda; Grobbelaar, Heleen; Napier, Carin E.
Food insecurity remains a significant challenge in sub-Saharan Africa. Improving food security in rural South Africa can be achieved by assisting smallholder farmers, offering agricultural loans, providing competent agricultural services, and promoting the consumption of indigenous leafy vegetables (ILVs). Studies indicate that ILVs can alleviate food and nutrition insecurity while enhancing dietary diversity, particularly among rural families. However, ILVs are still underutilised. This study investigated the seasonal patterns of ILV consumption and their role in household food security and daily nutrient intake recommendations in Mangangeni village, Ndwedwe, KwaZulu-Natal. A group of 118 participants (aged 18 and older) was selected through snowball sampling. Various questionnaires were employed, including those for demographic information, food frequency, 24-hour food recall, and food coping strategies. The data were analysed using the Statistical Package for the Social Sciences (SPSS) version 27, utilising descriptive statistics and one-way ANOVA for comparative analysis. The findings revealed that women (62.7%) primarily handled food preparation. Many participants were unemployed and relied on family members for essential needs. ILVs such as Bidens pilosa, blackjack, black nightshade, and amaranth were mainly foraged from the wild, household gardens, or farms. Households regularly consumed approximately six ILVs, with most participants eating them at least once or twice a week. All participants perceived ILVs as healthy, cheaper than other vegetables, tasty, beneficial for preventing and regulating illnesses, high in nutrients, quick to cook, and energy-giving. Seasonal shifts in ILV consumption were noted, with higher levels in summer and spring and a decrease in autumn and winter due to limited availability. Nutrient intake assessments revealed high carbohydrate consumption and imbalances in micronutrients. The most common strategy for coping with food insecurity involved choosing less expensive foods, while the least common strategy was consuming seed stocks intended for planting. While ILV consumption is influenced by seasonal availability, the results indicate that ILVs are crucial for mitigating food insecurity in rural South Africa. Enhancing access to ILVs year-round and promoting a balanced diet could improve dietary intake and diversity.
A smartphone-based application for the colorimetric detection of lead in wastewater using gold nanoparticles
(2025) Kubheka, Penuel Nkanyezi; Mokhothu, Thabang Hendrica; Shange, Sindisiwe Fortunate; Mdluli, Phumlani Selby
This study was conducted to develop and validate a straightforward, selective, and efficient colorimetric optical sensor that relies on gold nanoparticles for the detection and quantification of Pb(II) in wastewater systems. Gold nanoparticles were synthesized by chemical reduction of gold(III) chloride trihydrate, with trisodium citrate as a stabilizing agent to prevent aggregation. The synthesized AuNPs were characterized by ultraviolet-visible (UV-Vis) spectroscopy and transmission electron microscopy (TEM), confirming a spherical morphology with an average diameter of approximately 20 nm and a characteristic surface plasmon resonance (SPR) peak at 520 nm. The detection mechanism was based on Pb(II)-induced nanoparticle aggregation, resulting in a visible color change from red to blue. Quantitative analysis was conducted using both UVVis spectroscopy and digital image processing in ImageJ. The method was further validated using spiked river and tap water samples across a concentration range of 0.1–20 mg/L. Selectivity was assessed in the presence of potential interfering ions, while colorimetric response was analysed using the CIE Lab* color space. The presence of Pb(II) resulted in a red shift in the UV-Vis spectra, with the identification of two distinct SPR peaks at 520 nm and 680 nm, confirming nanoparticle aggregation. The colorimetric sensor demonstrated a strong linear response over the concentration range of 0.0520.0 mg/L (R² = 0.9901), with a detection limit of 0.01 mg/L. The recovery studies yielded values of 93%-99% for the ImageJ method and 88%-98% for the UV-Vis method. The Analysis of wastewater samples revealed Pb(II) concentrations ranging from 0.0 to 0.0379 mg/L. Then, minimal interference from other metal ions (Cr, Cu, Fe, Ni, Zn, Mn) was observed, indicating high selectivity. Colour analysis showed a systematic transition from red to green in the CIE Lab* space, with increasing Pb(II) concentration strongly correlating with measurable colour variation. The colorimetric sensor based on AuNPs developed provides a swift, cost-efficient, and exceptionally selective means for detecting Pb(II) in wastewater. The robust alignment between ImageJ and UV-Vis results indicates that smartphone image analysis can serve as a reliable alternative to standard spectrophotometric techniques. This strategy holds significant potential for on-site environmental assessments and in settings with limited resources.
Metagenomic fingerprinting of waterborne enteric viruses and their inhibition using phyto-nanomaterials
(2025) Lanrewaju, Adedayo Ayodeji; Swalaha, Feroz Mahomed; Folami, Abimbola Motunrayo; Sabiu, Saheed
Waterborne enteric viruses are major causes of diseases including gastroenteritis, hepatitis, encephalitis, meningitis, conjunctivitis, and respiratory disorders. Transmission occurs primarily through the faecal-oral channel via contaminated water or food, constituting significant public health risks. These viruses have been reported in South Africa following exposure to contaminated surface waters, dams, and wastewater. Nevertheless, limited data exist on their prevalence, diversity and abundance, especially in wastewater treatment plants (WWTPs) in eThekwini Municipality, Durban, KwaZulu-Natal, South Africa, necessitating metagenomic surveillance. In addition, the development of resistance to conventional drugs and high treatment costs necessitates the development of novel approaches to identify inexpensive and efficient antiviral medications. Interestingly, Spondias mombin and Macaranga barteri extracts have exhibited antiviral activity against several enteric viruses while Dicerocaryum eriocarpum with reported antibacterial activity remain unexplored as a reservoir of antiviral drug candidates. Accordingly, for the first time, this study profile the prevalence and diversity of viral families, including human and plant pathogenic viruses at the selected WWTPs and receiving rivers in eThekwini, Durban, Kwazulu-Natal, South Africa, using metagenomics next-generation sequencing (mNGS) approach and evaluates metabolites from S. mombin, M. barteri and D. eriocarpum against severe acute respiratory syndromecoronavirus-2 (SARS-CoV-2) and rotavirus A (RVA) using in silico techniques. The mNGS viral surveillance investigation identified viral families with a wide range of hosts including vertebrates (19.46%), plant (6.89%), insect (1.90%), fungal (0.13%), unclassified (7.25%) and phages (64.37%). Altogether, 30 viral families encompassing 26 different human pathogenic viral species were identified including enteroviruses, hepatovirus A, rotavirus A, norovirus, and astrovirus A. Conversely, plant viruses accounted for eight families dominated by the Virgaviridae. Most phytopathogenic reads belonged to the Tobamovirus genus, with additional representation from the family Bromoviridae detected across all sampling sites except RIVER4. These findings highlight the significance of wastewater surveillance in tracking known infections and unveiling possible emerging viral threats. RVA, one of the commonest waterborne enteric viruses detected in this study and SARS-CoV-2, although not detected in this study, probably due to low circulation within the communities at the time of sampling, were selected due to their clinical relevance and therapeutic limitations for in silico drug discovery from selected antiviral plants (S. mombin, M. barteri and D. eriocarpum). Molecular docking identified top-ranked compounds with higher negative docking scores against SARS-CoV-2 and RVA targets from the 77 pooled metabolites identified from the three selected medicinal plants against each of the investigated targets [main protease and RNAdependent RNA polymerase (RdRp)] of SARS-CoV-2 and RVA [capsid protein (VP7A, VP7C, VP7D), RdRp (VP1), spike protein (VP5*, VP8*)]. A minimum of three top-ranked compounds were subsequently identified owing to their physicochemical, pharmacokinetic and toxicological profiles suitable for drug development. The profiled top ranked compounds against the selected druggable targets of SARS-CoV-2 and RVA were subsequently subjected to 120-ns molecular dynamics (MD) simulations using the in-house HEAL1361 program with the Amber 18 package of the Centre for High Performance Computing (CHPC), South Africa. At least three of the top-ranked compounds exhibited higher negative binding free energy across the evaluated targets, suggesting structural and thermodynamic compatibility of the ligands at the binding domain of the targets and their suitability for drug development thereby validating the antiviral potential of the selected medicinal plants. However, against SCMP, only quercetin 3-O-rhamnoside had a higher negative binding free energy, suggesting the need for optimization of other metabolites. Notably, chrysoeriol7-glucuronide and spiraeoside demonstrated broad-spectrum affinity for RdRp of SARS-CoV-2 and RVA. Furthermore, (2S)- 6-(gamma,gamma-dimethylallyl)-3’,4’-dimethoxy-6’’,6’’- dimethylpyran[2’’,3’’:7,8]flavanone (2SG) and sericetin had better broad-spectrum affinities for both RVA VP5* and VP8*, while 2SG, apigenin-4 ′-glucoside and gnetin L exhibited better broad-spectrum affinities for RVA VP7A, VP7C and VP7D, suggesting their potential as multitarget antiviral candidates. However, some compounds induce higher thermodynamic entropy within the proteins relative to the standard. For instance, against VP5*, 2SG (-20.98 kcal/mol, 1.88 Å), sericetin (-20.46 kcal/mol, 1.93 Å) and sacranoside (-16.96 kcal/mol, 1.50 Å), though having higher negative binding free energies, exhibited higher RMSD values compared to the standard (1.30 Å) and unbound VP5* (1.45 Å). A partly similar trend was illustrated against VP8*, where sericetin (-18.31 kcal/mol, 1.27 Å) and 2SG (-20.98 kcal/mol, 1.18 Å) exhibited higher negative binding free energies yet had higher RMSD and RMSF values respectively, compared to the standard (1.19 Å, 1.01 Å). This observation highlights the need for optimizing these leads to improve their thermodynamic stability while boosting their affinity for the target proteins. Thus, due to their critical role in viral entry and infection, silver complexation optimization was limited to VP5* and VP8* of RVA to block the first and most vulnerable stage of infection. Accordingly, the silver complexation approach was employed to model possible silver nanoparticle conjugates for each lead compound, treating the compound as the reducing and capping agent. Thereafter, the effect of the complexation was evaluated whether complexation of the lead compound with silver enhances their binding affinity in silico. Improved binding affinity enhances drug activity through silver complexation which help mitigate drug resistance, broaden activity spectrum and enhance potency in vitro and in vivo. Thus, the study adopted silver complexation approach by conjugating silver with identified lead compounds against VP5* and VP8* via in silico modelling to achieve improved activity, reduced toxicity and maintain favorable pharmacokinetic profiles. To comprehend the effect of the complexation, quantum chemical calculations (density functional theory) were used to compare the molecular features of the silver-complexed leads against the lead compounds alongside assessment of drug-likeness and toxicity profiles. Thereafter, 12 and 19 silvercomplexed leads were docked against VP5* and VP8* respectively, followed by comparative interaction analysis between lead and silver-complexed compounds. Notably, the silvercomplexed leads exhibited enhanced molecular properties, suggesting better reactivity than their corresponding lead compounds without significantly altering their pharmacokinetic properties and toxicity profiles; hence, they remain suitable for drug development. Remarkably, higher negative docking scores were observed in all silver-complexed leads docked against VP5* compared to their corresponding lead compounds, except in the sacranoside A series. Conversely, lower negative docking scores were reported in the apigenin-4'-glucoside series, gnetin L A-E, and sericetin B relative to their lead compounds, while the remaining silvercomplexed leads exhibited improved binding affinity. Comparative interaction analysis identified 2SGC (-6.59 kcal/mol) and 2SGA (-6.77 kcal/mol) against VP5* and 2SGC (-8.06 kcal/mol) and SERA (-7.26 kcal/mol) against VP8* as promising candidates. Further computational investigation, including MD simulation, is recommended to elucidate the thermodynamics profile of the resulting protein and silver-complexed leads. Summarily, the observed enhanced binding capability of the silver-complexed leads could be attributed to their higher reactivity and increased interactions with essential amino acids at the binding pocket of the targets investigated. To validate the therapeutic potential of the profiled silver-complexed leads in combating viral infections, complementary in vitro and in vivo studies are strongly recommended.
Production of mycosporine-like amino acids from Euhalothece sp. for use as a photoprotectant
(2025) Mahmud, Uwais; Rawat, Ismail; Mogany, Trisha; Bux, Faizal
Protecting skin from harmful UV radiation is a well-recognized health imperative. Given that UV exposure is a primary cause of sunburn, premature skin aging, and significantly increases the risk of skin cancers including melanoma, the use of sunscreens has become a vital tool in public health strategies, leading to their widespread use. Whilst effective, there are concerns about the longterm effects of synthetic sunscreen ingredients that are driving the search for natural alternatives. Cyanobacteria are constantly exposed to short-wave ultraviolet (UV) radiation as they require solar energy to perform processes such as photosynthesis and nitrogen fixation. These microorganisms have developed multiple UV defence mechanisms to protect themselves from the higher amounts of UV radiation in the environment. Some of these strategies include mat formation, active repair mechanisms, accumulation of detoxifying enzymes and antioxidants, and synthesis of photo-protectants such as mycosporine-like amino acids (MAAs) (Rastogi et al., 2014). Mycosporine-like amino acids have gained a lot of interest in cosmetics and pharmaceutical industries since they act as natural photoprotectants and have shown to aid in overcoming rashes, pigmentation, aging as well as possess anticancer properties. Mycosporine-like amino acids are secondary metabolites produced by cyanobacteria in response to environmental stress such as salinity, temperature, high light irradiance and UV wavelengths. Cyanobacteria are a good source of MAAs, can be easily cultivated and requires a very short generation time, making them an environmentally friendly source of alternate photoprotectants. This study focuses on elucidating factors affecting MAA production using indigenous halophilic cyanobacteria Euhalothece sp. Light, salinity, and nitrogen concentration were optimised using response surface methodology to maximise MAA production. UV light irradiance was used to further induce expression of the protein. DNA was extracted and purified for gene expression analysis targeting the mys gene cluster. Purified MAAs were tested for their antioxidant activity and their stability under a range of temperatures, pH and UV irradiance to assess their potential for commercial use. Preliminary experiments confirmed the individual influence of abiotic factors, with light and salinity significantly impacting MAA production (p = 0,0395 and p = 0,0009 respectively). Using response surface methodology (RSM), the effects of light irradiance, salinity, nitrogen concentration, and UV exposure were optimized. A significant model (p = 0,0099) was developed, predicting optimal MAA production under 92 hours of UV exposure, nitrogen deficiency, and high salinity (90 or 120 g/L). Using 90 g/L salt was more cost-effective, requiring 28% less salt for a 5,36% reduction in MAA production. Molecular analysis through PCR confirmed the presence of the MAA biosynthetic gene cluster utilizing the OMT and DHQS and demonstrated its upregulation in response to UV exposure through qPCR. The UV-exposed culture showed amplification around cycle 14 while the control showed amplification around cycle 26. Purified MAAs demonstrated antioxidant activity and high stability across varying conditions over 48 hours. This included room temperature and neutral pH (p = 0,02), 4°C (p = 0,046), 40°C (p = 0,041) and UV irradiance (p = 0,04). These compounds showed excellent stability across various conditions, effectively maintaining their protective abilities. While their antioxidant capacity was measured (50,15%), it was clear that the main strength of MAAs lies in their strong UV protecting ability, making them highly suitable as active ingredients. This study demonstrates the potential of MAAs from Euhalothece sp. as a highly stable, effective, naturally derived, and industrially viable product. The optimized culture conditions, validated by molecular techniques, coupled with the high stability and additional beneficial properties of MAAs, position them as a compelling natural resource. Mycosporine-like amino acids can significantly advance photoprotection strategies and offer several other valuable applications in the cosmetic and pharmaceutical industries.
Characterisation and antiproliferative effect of okra seed protein isolate on human cancer cell lines
(2025) Maistry, Letisha; Mellem, John Jason; Gerrano, Abe Shegro
The increasing interest in plant-derived bioactive compounds has led to significant focus on okra seed protein isolate (OSPI) due to its notable nutritional and therapeutic properties. This research explores the structural and molecular characteristics of OSPI, aiming to assess its potential application as a nutraceutical in cancer therapy. A comprehensive amino acid profile showed that OSPI is rich in glutamic acid (14.46 g/100g), aspartic acid (7.56 g/100g), and arginine (9.42 g/100g), with a high proportion of hydrophobic (31.39 g/100g), and branched-chain amino acids (14.24 g/100g), known to support immune modulation and antitumour activity. Solubility analysis demonstrated peak protein solubility (91.86%) at pH 9, which is a critical factor affecting its functional efficacy. Molecular weight profiling indicated the presence of 7S and 11S globulin polypeptides, which are associated with encapsulation efficiency in nutraceutical development. Spectroscopic analysis, including FTIR and XRD, established the presence of α-helices and β-sheet structures, further supporting the protein’s conformational stability and amorphous nature, promoting bioavailability in pharmaceutical formulations. Particle size denoted monomodal distributions with the smallest size depicted at 0.144±0.10 µm, highlighting its suitability in drug delivery systems. The cytotoxic and antiproliferative effect of OSPI was evaluated using human cancer cell lines. In lung carcinoma cells (A549), OSPI reduced viability to 37.73% at 15 µg/mL and demonstrated a lower IC50 (21.80 µg/mL) than the standard chemotherapeutic agent camptothecin (524.85 µg/mL). Defatted okra flour (DOF) and OSPI significantly upregulated p53 levels with apoptotic induction against A549, as presented by Annexin V-binding. In hepatocellular carcinoma cells (Hep-G2), OSPI activated caspase-3/7, -8, and -9 at levels comparable to camptothecin, suggesting the initiation of both intrinsic and extrinsic apoptotic pathways. Furthermore, okra flour (OF) promoted reactive oxygen species (ROS) generation more effectively than camptothecin in A549 and Hep-G2 cells, reinforcing its potential oxidative stress-mediated apoptotic effects. These findings collectively underscore OSPI as a potential candidate for pharmaceutical and nutraceutical applications, particularly in cancer therapy. Its structural stability, solubility, and bioactive profile support its utilisation in the development of plant-based therapeutic interventions.
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.

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