Research Articles (Biotechnology)

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Heteroleptic bis(benzazole) ruthenium complexes: structural characterization, DNA/BSA binding, and anticancer studies
(Taylor and Francis Ltd., 2026) Tsaulwayo, Nokwanda; Moabelo, Koena; Meyer, Mervin
The reactions of 2,6-bis(benzimidazol-2-yl)pyridine (HL1) and 2,6-bis(benzothiazol-2-yl)pyridine (HL2) with RuCl3.3H2O afforded complexes [Ru(L1)Cl3] (Ru1) and [Ru(L2)Cl3] (Ru2), respectively. Subsequent treatment of complex Ru1 with DMSO led to the generation of the cationic heteroleptic Ru(II) complex [Ru(L1)(DMSO)2(Cl)] (Ru3). Separately, reactions of complexes Ru1 or Ru2 with 2,2′-bipyridine (bpy) and 1,10-phenanthroline (phen) co-ligands led to the isolation of the heteroleptic Ru(II) complexes [Ru(L1)(bpy)(Cl)] (Ru4), [Ru(L2)(bpy)(Cl)]Cl (Ru5), and [Ru(L2)(phen)(Cl)]Cl (Ru6) in moderate yields. Solid structure of complex Ru3 established a tridentate coordination mode of L1, in which two DMSO and one chloro co-ligands complete the octahedral geometry. DNA binding studies of complexes Ru1 and Ru3–Ru6 indicated groove-binding interactions accompanied by partial intercalation, with complexes Ru4 and Ru6 showing the highest binding affinities. The bovine serum albumin (BSA) protein interaction occurred via a static quenching mechanism, as evidenced from the quenching constants (Kq) in the order of 1011 M−1. The biological potency of the ruthenium complexes was studied using Caco-2 and MCF-7 cancer cell lines and normal cell lines HeK293 and KMST-6. Complex Ru1 demonstrated moderate cytotoxicity and selectivity against MCF-7 cancer cell line (IC50 of 12.30 μM and SI of 4.74), while the heteroleptic ruthenium complexes Ru3 - Ru6 displayed very low biological activities.
Ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry metabolomic profiling reveals harvest age dependent changes in the roots of Pelargonium sidoides DC
(Springer, 2026-08) Takalani Mulaudzi; Kundani Khameli; Muinat Nike Lewu
Introduction: Cultivation of medicinal plants provides an opportunity for economic gain and health care accessibility. Ensuring consistent quality plant material is important for plants such as Pelargonium sidoides DC used for production of phytomedicines that are available in local and international markets. There is limited research on how agronomic factors affects phytochemicals in P. sidoides roots. Objective: To evaluate the effect of different irrigation regimes and harvesting age on metabolite accumulation in dried roots of P. sidoides. Methodology: Irrigation was applied at 75%, 50% and 25% plant available water (PAW) corresponding to well- watered, moderate water deficit and severe water deficit respectively. P. sidoides, which were harvested at 6, 12 and 18 months after imposing the different water deficit treatments, roots dried and subjected to ultra-performance liquid chromatography -quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS) coupled with multivariate statistical analysis. Results: Unsupervised multivariate analysis showed that irrigation did not affect the obtained metabolic features. Orthogonal partial least squares discriminant analysis (OPLS-DA) showed statistically significance difference between 6 versus 12- and 18- months harvest ages. Compounds such as umckalin, epigallocatechin dimer, and gallic acid were increased in 12 and 18 months compared to the 6 months harvest. Sucrose/trehalose was increased by 0.2431- and 0.560- fold in 6 months compared to 12- and 18-months harvest ages respectively. On quantification, umckalin increased from 260.40 mg/kg DW at 6 months to 431.61 mg/kg DW at 12 months, while epigallocatechin rose from 342.98 mg/kg DW to 505.58 mg/kg DW over the same period. Umckalin sulphate was highest at 6 months under 25% PAW (7110.32 mg/kg DW) and decreased at 12 months harvest under the same irrigation level (4522.05 mg/kg DW). Conclusion: The results indicated that younger plants accumulated more primary metabolites and modified secondary metabolites, whereas older plants accumulate more secondary metabolites. Moreover, cultivation of P. sidoides in limited water is plausible.
Engineering natural Saccharomyces cerevisiae isolates for enhanced one-step cellulosic ethanol production
(Springer Science and Business Media Deutschland GmbH, 2026) Minnaar, Letitia Sabina; den Haan, Riaan; Inokuma, Kentaro
Engineering yeast strains for use as chassis organisms in second-generation (2G) bioethanol is a promising strategy to improve process economics. Natural isolates of Saccharomyces cerevisiae offer strain backgrounds with greater genetic diversity and enhanced robustness, with the potential for improved heterologous protein production capabilities. In this study, heterologous cellulase production using different expression strategies was evaluated in various process-relevant conditions. Enhanced cellulolytic activity was clearly demonstrated in a cell-tethered enzyme system, compared to a free enzyme system, across identical strain backgrounds. Superior secretory capacity was obtained for YI59_V2 for all individual enzymes across all process-relevant conditions tested. In addition, this strain exhibited improved hydrolysis efficiency and ethanol production from crystalline cellulose, achieving ~10 g/L after 96 h (~88% of the maximum theoretical yield) without the need for exogenous cellulase supplementation. Interestingly, enhanced strain robustness against process-relevant, secretion, and cell wall stresses was also observed in transformants with cell-tethered cellulase systems compared to those with free enzyme systems. This study highlights that the expression design strategy for cellulase-encoding genes in this natural isolate was pivotal for increasing protein titres and for influencing strain robustness. Strains exhibiting elevated cellulase activity and increased robustness represent a key step toward the industrial deployment of consolidated bioprocessing (CBP). Key points: • Cell-tethered expression greatly boosted cellulase activity and cellulose breakdown. • YI59_V2 yielded ~ 10 g/L ethanol from crystalline cellulose without added enzymes. • Tethered enzymes reshaped cell walls and altered stress tolerance
Transcriptome profiling of leaves and roots from rooibos (aspalathus linearis) using oxford nanopore sequencing
(Multidisciplinary Digital Publishing Institute (MDPI), 2026) Beckett, Tanweer; Hesse, Uljana
Rooibos (Aspalathus linearis) is one of the few endemic South African plants that has achieved economic importance and international acclaim, mostly as a herbal tea. Plant production, limited to a small mountainous region in South Africa, is at risk as commercial rooibos longevity is in decline, mostly due to low stress tolerance. Transcriptome data can serve to identify molecular markers for improved stress response, which would speed up selection and facilitate the establishment of breeding programmes. Previously, rooibos leaf transcriptomes have been sequenced using Illumina, which yields short reads, hampering correct reassembly of full-length transcripts. Here, we established Oxford Nanopore-based, long-read transcriptome analysis for leaf and root samples from rooibos. We report on potential pitfalls in data pre-processing (PolyA tail trimming and rRNA removal), and compare two assemblers (RATTLE and RNA-Bloom2) and two clustering algorithms (VSEARCH and CD-HIT). The best assembly comprising 169,122 transcripts was generated using RNA-Bloom2 with short-read polishing, followed by CD-HIT clustering. Of the 95,054 predicted proteins, only 67% were also present in the Illumina dataset. The remainder comprised substantially shorter, mostly full-length sequences from a wide range of primary and secondary biosynthesis pathways. Functional annotation indicated that this transcriptome represents a high-quality, comprehensive resource for data mining.
Integration of enzyme immobilization and multi-enzyme hydrolysis to enhance saccharification efficiency and ethanol yield in sorghum fermentation systems
(Springer, 2026) Adeyanju, Muinat M.; Ademakinwa, Adedeji N.; Alli, Kazeem O.; Adefuye, Adefemi O.; Omirin, Emmanuel Sunday; Olalekan, Samuel O.
The suboptimal ethanol yield in “Burukutu,” a traditional sorghum-based alcoholic beverage, stems from the recalcitrance of the grain’s starch–protein matrix to enzymatic hydrolysis. This study compared the performance of free and alginate-entrapped (2% w/v) α-amylase, glucoamylase, and protease, applied in various combinations, to optimize saccharification kinetics and bioethanol productivity in red and white sorghum cultivars. Results indicated that the triple-enzyme cocktail (α-amylase + glucoamylase + protease) was significantly superior to individual or dual-enzyme systems (F = 3740.50, p < 0.001), emphasizing the critical role of protease in deconstructing the protein barrier to enhance starch accessibility. Red sorghum exhibited significantly higher saccharification depth and ethanol titers than the white cultivar (p < 0.001), likely due to cultivar-specific differences in grain architecture. Peak ethanol concentrations reached 35.3 ± 0.2% v/v in red sorghum using the free triple-enzyme system, while the immobilized system achieved 29.70 ± 0.36% v/v at 72 h. Notably, the immobilized biocatalysts demonstrated robust operational stability, maintaining high sugar utilization efficiencies (> 85%) through six consecutive fermentation cycles. While a gradual decline in efficiency was observed (F = 151.95, p < 0.001), the immobilized multi-enzyme framework retained substantial activity, particularly in the red sorghum matrix. These findings demonstrate that synergistic multi-enzyme immobilization substantially improves starch-to-ethanol conversion and process sustainability, offering a scalable model for intensifying sorghum-based bioethanol production.
Production of depolymerised xylooligosaccharides via steam explosion and enzymatic hydrolysis of brewers’ spent grain
(Springer Science and Business Media B.V., 2026) Arries, Chelsey B.; den Haan, Riaan; Bosman, Catharine E.
Purpose: Brewers’ spent grain (BSG) is a major processing residue from the beer brewing industry, often applied for low-value animal feed or, process energy, or otherwise disposed. The processing of BSG into xylooligosaccharides (XOS), a proven prebiotic with application in the food, beverage and health industries, can be achieved through selective solubilisation/hydrolysis of its hemicellulose content. Methods: In this study, the sequential processing of BSG to maximise the yield of XOS was achieved by screw-pressing to remove a protein-rich press liquid fraction, followed by steam explosion pretreatment prior to enzymatic hydrolysis of the remaining hemicellulose in the feedstock. Results: A combined XOS yield of 37% (kg XOS/kg hemicellulose) was achieved from the steam explosion liquor (two-thirds) and the enzymatic hydrolysis of pretreated solids (one-third). The crude, longer-chain XOS products were subsequently depolymerised through an additional enzymatic hydrolysis step, to achieve the desired XOS molecules with degrees of polymerisation between 2 and 3, resulting in an overall XOS yield of 16%. Conclusion: The overall XOS yield was increased by adding enzymatic hydrolysis of the solids fraction to the XOS production process, however, the findings of the study presented a potential trade-off between the increase in XOS yield and the cost of the increased enzyme requirements.
Green-synthesized bimetallic zinc ferrite (franklinite) nanoparticles prevent drought-induced growth reduction and oxidative stress in sorghum bicolor through improved nutrient content and the antioxidant defense
(Elsevier B.V., 2026) Ndou, Nzumbululo; Gavhi, Pfunzo; Nkuna, Mulisa; Ikebudu, Vivian Chigozie; Faro, Andrew; Ngece-Ajayi, Rachel Fanelwa; Mulaudzi-Masuku, Takalani
Sorghum bicolor (L.) Moench is a cereal crop renowned for its ability to moderately tolerate drought stress, however prolonged and severe droughts can affect its growth and yield. This study reports on the dual role of green-synthesized bimetallic Zinc-Iron Oxide (ZnFe2O4 NPs) nanoparticles (NPs), which are to enhance sorghum growth and mitigate oxidative damage under drought stress. The 34 nm ZnFe2O4 NPs synthesized from rooibos, were confirmed by an absorbance peak at 296 nm, a Fourier-Transform-Infrared Spectroscopy peak at 547 cm−1, and characterized by a crystallized face-centered-franklinite nature. Sorghum seedlings germinated from seeds primed with different ZnFe2O4 NPs concentrations of 5 mg/L, 10 mg/L, and 15 mg/L, were established for 14 days, followed by withholding water for 7 days to induce drought stress. Drought led to a decrease in shoot length (SL), fresh weight (FW), dry weight (DW), and total chlorophyll (Chlt) content by 43.6 %, 58.0 %, 63.9 % and 45.0 % respectively. These decreases correlated with the alteration of vascular bundle tissues causing nutrient imbalances, overaccumulation of reactive oxygen species, and lipid peroxidation thus inducing oxidative damage in sorghum seedlings. However, priming with NPs particularly, 15 mg/L ZnFe2O4 NPs, increased SL (138 %), FW (251.23 %), DW (251 %), and Chlt (104 %), and effectively reduced oxidative stress, through the improved antioxidant activity. The results suggest that ZnFe2O4 NPs can be employed as a strategy to prevent the harmful effects of drought stress, while improving crop growth.
Peptide-functionalized gold nanoparticles lowered diet-induced obesity in rats by reducing white adipose tissue mass
(Institute of Physics, 2026) Modise, Keletso; Sibuyi, Nicole Remaliah Samantha; Madiehe, Madimabe Abram; Meyer, Mervin; Meyer, Samantha; Fadaka, Adewale Oluwaseun; Gabuza, Kwazi B
Anti-obesity drugs are limited in their application due to poor drug specificity, efficacy, and bystander side effects. The study reports on the use of bi-functionalized gold nanoparticles (AuNPs) to improve the selectivity and efficacy of therapeutic agents in obese male Wistar rats. Citrate-capped AuNPs (cAuNPs) were functionalized with Adipose Homing Peptide (AHP) and with or without a D(KLAKLAK)2 peptide (KLA); i.e., AuNP-AHP-KLA and AuNP-AHP, respectively. The rats were grouped into lean (low fat, LF), obesity-resistant (high fat, HF1), and three groups (HF2, HF3 and HF4) from obesity-prone rats. Rats were intravenously injected every third day for four weeks with their respective treatments; phosphate buffered saline (LF and HF2), AuNP-AHP-KLA (HF1 and HF4), and AuNP-AHP (HF3). Urinalysis was performed during the first and the fourth week of treatments. Oral Glucose Tolerance Test (OGTT) was performed after the third week of treatment. AuNPs distribution in white adipose tissues (WATs) and the liver of rats on HF1, HF3 and HF4 groups was analyzed by inductively coupled plasma mass spectrometry (ICP-MS). Treatment with AuNP-AHP-KLA (HF4) reduced the body weight and adipose tissue mass of the obese rats in HF4, and improved their glucose tolerance. Urinalysis showed that the AuNPs conjugates did not cause any toxicity to the rats after four weeks of treatment. High content of gold (Au) was detected in the WATs of HF3 group treated with AuNP-AHP, and negligible amount of Au was found in the HF1 and HF4 groups treated with AuNP-AHP-KLA. The preliminary data confirmed that bifunctionalized-AuNPs can potentially be effective theranostic tools for obesity treatment. Further studies are underway to determine the histological and molecular effects of this targeted nanotherapy.
Forensic inference in Africa: Evaluating population structure, databases, and regional assignment accuracy
(Elsevier Ireland Ltd, 2026) Kasu, Mohaimin; Morrow, Jessica Caroline Anne; Lesaoana, Mpasi; Brydon, Humphrey; D’Amato, Maria Eugenia
This study reports novel 21 aSTR (autosomal Short Tandem Repeats) allele frequencies from 538 individuals, as well as 11 triallelic profiles, representing seven Bantu-speaking groups in Southern Africa (Ndebele, Pedi, Phuthi, Tsonga, Sotho, Swati, and Xhosa). These data contributed to a comprehensive representation of the Southern Bantu (SB). The defined SB reference database was evaluated for various forensic uses and applications: extant diversity, population structure, adequacy of alternative reference databases, and continental biogeographical ancestry prediction.Different analytical methods—including summary statistics, multivariate analyses (Multidimensional Scaling, MDS; Discriminant Analysis of Principal Components, DAPC), and Bayesian clustering—detected continental structure, identifying four major clusters: Southern, Eastern, Western, and Horn of Africa.This observation motivated the evaluation of two practical applications of this information: one methodological (alternative reference frequency database) and one predictive (biogeographic assignment). The adequacy of alternative reference databases for representing SB populations—STRidER South Africa, STRidER Africa, African American, and global datasets—was assessed by comparing reciprocal allelic coverage and shifts in random match probabilities (RMPs). Of the databases tested, the STRidER Africa database provided the closest representation of the SB. Population-level analyses evidenced the need for a stratification correction (θ = 0.005 or 0.01) for SB populations.Intracontinental biogeographic prediction was assessed using an XGBoost machine learning classification model across four major African regions. The model’s predictive balanced accuracy ranged from 80 % to 94 % across African regions (94 % for the Horn of Africa, 87 % for Southern Africa, 84 % for Western Africa, and 80 % for Eastern Africa).The accuracy and limitations of this practice are discussed, along with its ethical implications. The assessment of reference databases can be extended to more general applications across Africa.
AlphaMissense pathogenicity scores predict response to immunotherapy and enhances the predictive capability of tumor mutation burden
(Neoplasia Press, Inc., 2026) Fadaka, Adewale Oluwaseun; Sibuyi, Nicole Remaliah Samantha; Meyer, Mervin
Tumor Mutational Burden (TMB) is a widely used biomarker for selecting cancer patients for immune checkpoint inhibitor (ICI) therapy. However, TMB alone has limited predictive power, as it fails to account for the functional impact of mutations. We introduce AlphaTMB, a composite biomarker that integrates the quantity of mutations (TMB) with the qualitative assessment of their pathogenicity using AlphaMissense, a deep learning model that predicts the deleteriousness of missense variants. Using a pan-cancer cohort of 1,662 patients from the MSK-IMPACT study who received ICI therapy, we computed three scores per patient: TMB, Alpha (sum of AlphaMissense scores), and AlphaTMB (product of TMB and Alpha). Patients were stratified using both cancer-specific and pan-cancer quantiles. Survival outcomes were evaluated using Kaplan-Meier and multivariate Cox proportional hazards models, controlling for cancer type, age, and ICI regimen. AlphaTMB showed strong correlation with TMB (Spearman ρ = 0.866, p < 0.001), but offered improved prognostic accuracy. Patients in the bottom 80% AlphaTMB group had significantly poorer survival than those in the top 10% (HR < 2.51, p < 0.001), outperforming TMB and Alpha alone. AlphaTMB reclassified borderline cases, identifying subsets with low TMB but high deleterious mutation load, and vice versa. Gene mutation heatmaps and co-occurrence analysis confirmed that to 10% AlphaTMB-high tumors were enriched in mismatch repair and POLE mutations, reflecting a neoantigen-rich, immunotherapy-responsive phenotype. AlphaTMB improves survival prediction beyond TMB alone, better captures immunogenic tumor profiles, and reflects more accurate patient stratification. This AI derived somatic mutations pathogenicity scoring represents a step toward personalized immuno-oncology and merits further validation in prospective studies.
In situ green synthesis of red wine silver nanoparticles on cotton fabrics and investigation of their antibacterial effects
(Mdpi, 2026) Erasmus , Alexandria; Sibuyi, Nicole; Meyer, Mervin
Antimicrobial resistance (AMR) is a major global health concern, which complicates treatment of microbial infections and wounds. Conventional therapies are no longer effective against drug resistant microbes; hence, novel antimicrobial approaches are urgently required. Silver nanoparticles (AgNPs) offer stronger antimicrobial activity, and in situ synthesis improves stability, uniformity, cost efficiency, and bioactivity while minimising contamination. These features make AgNPs well-suited for incorporation into textiles and wound dressings. Red wine extract (RW-E), rich in antioxidant and anti-inflammatory compounds was used to hydrothermally synthesise RW-AgNPs and RW-AgNPs-loaded on cotton (RWALC) by optimising pH and RW-E concentration. Characterisation was performed using UV–Vis spectroscopy, dynamic light scattering (DLS), and High Resolution and Scanning electron microscopy (HR-TEM and SEM). Antibacterial activities were evaluated against human pathogens through agar disc diffusion assay for RWALC and microdilution assay for RW-AgNPs. RWALC showed higher potency against both Gram-negative and Gram-positive bacteria, with inhibition zones of 12.33 ± 1.15 to 23.5 ± 5.15 mm, that surpassed those of ciprofloxacin (10 ± 3 to 19.17 ± 1.39 mm at 10 μg/mL). RW-AgNPs exhibited low minimum inhibitory concentrations (MIC: 0.195–3.125 μg/mL) and minimum bactericidal concentrations (MBC: 0.78–6.25 μg/mL). Preincubation with β-mercaptoethanol (β-ME) inhibited the antibacterial activity of RWALC, suggesting that thiolated molecules are involved in AgNPs-mediated effects. This study demonstrated that green-synthesised RW-AgNPs, incorporated in situ into cotton, conferred strong antibacterial properties, warranting further investigation into their mechanisms of action.
Drought Tolerance Mechanisms in Grain and Vegetable Amaranthus Species: Physiological, Biochemical and Molecular Insights
(Multidisciplinary Digital Publishing Institute (MDPI), 2025) Nkuna, Mulisa; Gavhi, Pfunzo; Kanyerere, Alice Mwanjiwa; Ikebudu, Vivian Chigozie; Ikebudu, Vivian Chigozie; Ndou, Nzumbululo; Faro, Andrew
Drought limits plant growth, development and productivity, leading to more than 50% crop loss globally. Drought-induced oxidative stress disturbs the plant’s metabolism; however, plants activate signaling pathways to respond and adapt to drought stress. Although drought response mechanisms are well reported in several crops, these mechanisms are poorly understood in Amaranthus. As a highly nutritious crop, rich in antioxidants with the ability to survive in extreme agro-climatic environments, Amaranthus has the potential to serve as a climate-smart future crop. This review provides evidence of some drought response traits in grain and vegetable Amaranthus species. Grain amaranths are the most tolerant species, mainly through improved osmoregulation, antioxidant capacity, and gene expression. While biomass partitioning, efficient water use, and membrane stability have been reported in both grain and vegetable amaranth, the molecular response of vegetable amaranth remains limited. Thus, future research must focus on integrated biochemical, molecular, and multi-omics applications to screen and identify resilient Amaranthus genotypes under drought for sustainable agriculture.
Advancing a circular bioeconomy: unlocking the potential of banana pseudostem for microbially-derived value-added products
(Elsevier B.V., 2025) Sewsynker-Sukai Y.; David, Anthea Naomi; Laltha, Milesh
Bananas have been touted as a vital food crop, that is typically cultivated under tropical climates and generates high volumes of wastes. Of particular interest, banana pseudostem (BP) is a lignocellulosic waste that is renewable, abundant and may serve as a low-cost carbon source for generating a spectrum of high-value bio-based products. However, high production costs have restricted its mainstream adoption. This review explores the suitability of BP as a bioprocessing substrate, assessing advances in pretreatment strategies for enhanced sugar recovery towards efficient downstream microbial conversion into value-added products. Additionally, comparative analysis of reported studies identifies the gaps encountered in bioprocess development and optimization, and highlights the opportunities for process integration and waste valorization. Beyond the bioprocessing stage, logistical constraints surrounding BP characteristics, decentralized availability, and transportation inefficiencies were summarized. Potential mitigation strategies such as localized biorefinery hubs, preprocessing, and integrated supply chain networks were critically discussed as pathways to improve substrate availability and process economics. Finally, the review outlines future prospects to integrate BP-based systems into circular bioeconomy models by coupling waste-based pretreatment optimization with value-added product recovery and sustainable logistics planning.
Sustainability assessment of succinic acid production using the biochar-mediated anaerobic fermentation
(Elsevier, 2025) den Haan Riaan; Chen Minjiao; Xiao Wenlong
Succinic acid is a bulk compound, which has been widely used in various areas. The anaerobic production of succinic acid by Escherichia coli suffers from the insufficient supply of reducing power, leading to the low titer and yield. This work adopted modified biochar to enhance bio-succinic acid production by E. coli Suc260. The integration of anaerobic fermentation with supplementation of cost-effective biochar in medium resulted in the highest succinic acid titer of 72.84 g/L along with reduced by-product, representing a remarkable yield of 93.03 %. Furthermore, results from Fourier transform infrared spectroscopy and scanning electron microscopy revealed the successful microbial attachment and growth within the biochar matrix. Notably, the addition of biochar enhanced the intracellular electron transport chain and maintained the intracellular metabolic balance, directing more metabolic flux towards the succinic acid synthesis. The energy and life-cycle assessment indicated that the energy consumption of the biochar-mediated fermentative succinic acid production process was 8.76 MJ/kgSA, and this process achieved a net negative carbon footprint of −0.651 kgCO2e/kgSA. This research highlights the great potential to leverage biochar for improving succinic acid biosynthesis through anaerobic fermentation. [Display omitted] •Biochar addition reduced acetic and formic acid by-product accumulation.•Fruitwood biochar most effectively promoted succinic acid production.•Biochar enhanced cell immobilization, pH buffering, and electron transfer.•The biochar-mediated process achieved net negative carbon emissions.
Identifying promoters to enhance heterologous gene expression in recombinant saccharomyces cerevisiae strains cultivated on non-native substrates
(Springer Science and Business Media Deutschland GmbH, 2025) Fortuin, Jordan; den Haan, Riaan
Abstract: Efficient bioconversion of lignocellulosic biomass (LCB) to ethanol by Saccharomyces cerevisiae requires its engineering to express heterologous enzymes at titres high enough to make significant impacts on industrial consolidated bioprocessing (CBP). Promoters are required for this purpose, but are reportedly influenced by various environmental factors as well as the protein specific nature of expression, warranting the need for assessment under the conditions for which they are intended. Heterologous xylosidase- and xylanase-encoding genes (xln43_SED1 and xyn2) were individually cloned under transcriptional control of the SED1P and TDH3P promoters, and DIT1T terminator, and integrated into the genome of an a S. cerevisiae strain engineered for xylose utilization. Enzymatic assays were used to quantify the performance of the promoters when strains were cultivated on glucose (aerobically and micro-aerobically) and xylose. Additional strains containing both xln43_SED1 and xyn2 under different promoter combinations were then used to allow direct fermentation of beechwood xylan to ethanol in a CBP. The SED1P/DIT1T and TDH3P/DIT1T combinations significantly outperformed the benchmark ENO1P/T under all of the tested cultivation conditions, as well as with regard to growth trials on non-native substrates (xylo-oligosaccharides/XOS and beechwood xylan) and fermentations of beechwood xylan to ethanol. Overall, TDH3P was the best-performing promoter. This study demonstrates that heterologous metabolic pathways and CBP can be significantly enhanced by employing carefully selected promoters tailored to specific conditions.
Characterization of Zalaria obscura Y1223 hydrolases: implications for lignocellulose conversion
(Springer Science and Business Media Deutschland GmbH, 2025) Boonzaier, Jeremy J.; den Haan, Riaan; Hart, Rodney S.
Overconsumption of fossil fuel reserves and its adverse effects has sparked interest in the production of second-generation biofuels due to the abundance of lignocellulosic waste and potential energy crops. However, processing costs associated with depolymerization of the cellulose crystalline structure have stalled advancement in cellulosic ethanol production. Current investigations range from identification of novel enzymes for lignocellulose hydrolysis to consolidation of enzyme production into a singular alcohol producing microorganism to potentially reduce cost for commercial processing. In this study, a total of 828 non-Saccharomyces and black yeasts were screened for cellulolytic and xylanolytic enzyme activities, whereby 60 isolates were identified that exhibited activity for at least one of the enzymes tested. In doing so, a novel Zalaria obscura strain (Z. obscura Y1223) was identified and assessed for enzyme activity in multiple growth media. Semi-quantitative assays showed that Z. obscura Y1223 produced cellulases optimally in media containing yeast extract, peptone and oat bran, with a pH range between pH 5 and 6 and at 30 °C. Maximum xylanase activity (20.5 U/L/OD600) was attained using synthetic complete media supplemented with xylo-oligosaccharides and maximum cellulase activity (7.51 U/L/OD600 endoglucanase, 1.302 U/L/OD600 β-glucosidase) was attained when grown in media containing yeast extract, peptone and oat bran. To our knowledge, this is the first study to quantify the cellulolytic and xylanolytic enzyme activities of a Zalaria spp., which provides key insight into the availability of unexplored cellulolytic enzymes that could inform the design of organisms engineered for consolidated bioprocessing.
Ferrocene-based hybrid drugs as potential anticancer and antibacterial therapeutic agents for incorporation into nanocarriers: in silico, in vitro, molecular docking evaluations
(MDPI AG, 2025) Oselusi Samson; Peter Sijongesonke; Morifi Eric; Nwamadi Mutshinyalo
Cancer and bacterial cases are increasing. Hence, new drugs to treat these diseases are paramount. Ferrocene-based hybrid compounds were synthesizedas potential cancer and bacteria therapeutics. The synthesized compounds were characterized via FTIR, NMR, and LC-MS and evaluated against different cancer cells and bacterial strains. Moreover, computational studies of these compounds were conducted using several silico tools. Among the synthesized compounds, hybrid 10 was the most promising compound, displaying promising anticancer activity with IC50 values between 42.42 and 45.37 and 50.64 and 73.37 µg/mL against HeLa and CHO cancer cells, respectively, with a selective index greater than one on HeLa cancer cells. Compounds 22–26 displayed promising antibacterial activity with a MIC value of 7.8125 µg/mL against most bacterial strains in vitro. The in silico results revealed that this compound has strong binding affinities for 4qtb, 3eqm, and 2w3l cervical cancer proteins, exhibiting binding energies of −7.3, −8.7, and 7.4 kcal/mol, respectively. Furthermore, hybrid 10 showed promising pharmacokinetics and drug-like properties, including high GI absorption, moderate water solubility, favoring the oral administration route, nontoxicity, and is a P-gp substrate. The findings obtained in this study illustrate that hybrid compounds are potential therapeutics that need to be explored. The compounds also contained functionalities relevant for incorporating into nanocarriers to improve their biological activities further. Therefore, further studies are recommended for the most effective compounds to reinforce these findings.
Phytochemical characterization and cytotoxicity effects of Hyptis suaveolens collected in Nigeria
(Elsevier B.V., 2025) Pearce, Keenau; Benjeddou, Mongi; Azeez, Olatunji G
Hyptis suaveleons (L.) Poit. belongs to the Laminaceae family. This weed, native to tropical America, has become widespread in tropical regions worldwide. In folk medicine, plant extracts are used in the treatment of wounds, peptic ulcers, respiratory tract infections, and skin diseases among others. Thus, the importance of assessing the toxicity of plants for any human use cannot be overstated. This study analyzed the phytochemical properties of the Nigerian H. suaveleons population and assessed its cytotoxicity. Six bioactive compounds were isolated from the acetone extract of the H. suaveolens plant using silica gel column chromatography, one of which is new from natural sources. The isolated compounds were identified as 14-O-acetyl suaveolol (C1), suaveolol (C2), suaveolic acid (C3), dehydroabietinol (C4), maniladiol (C5), and β-sitosterol (C6) based on 1D and 2D NMR spectroscopic data. The MTT assay was used to assess the cytotoxicity effects of these metabolites on HepG2, KMST-6, and HaCaT cells. Among them, C1 significantly reduced HepG2, KMST-6, and HaCaT cell viability with IC50 values of 35.97, 43.48, and 65.10 µg/ml, respectively. The study suggests C1 has promising anticancer properties, possibly due to the acetyl group on C-14, while C2, suaveolol, lacks this group, and did not yield any inhibitory activities. However, further research is needed to understand its mechanisms.
Biomolecular affinities and cytotoxicity of copper(I) and silver(I) phosphine–pyridinyl complexes against CACO-2 and CASKI cell lines
(John Wiley and Sons Inc, 2025) Meyer, Miche D; Sibuyi, Nicole R. S; Onani, Martin O
A series of three copper (I) and three silver (I) complexes with the general formula [M L(PPh3)2]NO3, (M = Cu for complexes 1–3 and Ag for complexes 4–6) are synthesized by reacting copper(I) or silver(I)-nitrate and triphenylphosphine with the bidentate ligands, (E)-1-(pyridin-2-yl)-N-(o-tolyl)methanimine L1, (E)-N-isopropyl-1-(pyridine-2-yl)methanimine L2, or (E)-N-(2,6-dimethylphenyl)-1-(pyridine-2-yl)methanimine L3. The structures of these complexes are elucidated using a combination of NMR spectroscopy, FTIR, UV–visible, mass spectrometry, elemental analysis, and single-crystal X-ray diffraction. Structural analysis revealed that the Schiff bases coordinate to the metal centers in a bidentate fashion, with triphenylphosphine occupying the remaining coordination sites in complexes 1, 2, and 5. In contrast, in complexes 3, 4, and 6, one coordination site is occupied by a nitrate anion instead of triphenylphosphine. All six complexes exhibit a distorted tetrahedral geometry around the metal center, as confirmed by τ4 values ranging from 0.54 to 0.87. Binding studies with calf-thymus DNA demonstrated that complexes 1–6 interact via intercalation, with complex 5 exhibiting the highest binding constant. Furthermore, all complexes showed strong binding affinity toward bovine serum albumin. Cytotoxicity studies revealed significant cytotoxicity of complexes 1–6 against human colon adenocarcinoma (Caco-2) and human cervical epidermoid carcinoma (Caski) cell lines.
Glucoselipid biosurfactant biosynthesis operon of rouxiella badensis DSM 100043T: screening, identification, and heterologous expression in escherichia coli
(Multidisciplinary Digital Publishing Institute (MDPI), 2025) Van Zyl Leonardo; Williams Wesley; Burger Anita; Harahap Andre
Rouxiella badensis DSM 100043T had been previously proven to produce a novel glucoselipid biosurfactant which has a very low critical micelle concentration (CMC) as well as very good stability against a wide range of pH, temperature, and salinity. In this study, we performed a function-based library screening from a R. badensis DSM 100043T genome library to identify responsible genes for biosynthesis of this glucoselipid. The identified open reading frames (ORFs) were cloned into several constructs in Escherichia coli for gene permutation analysis and the individual products were analyzed using high-performance thin-layer chromatography (HPTLC). Products of interest from positive expression strains were purified and analyzed by liquid chromatography/electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) and nuclear magnetic resonance (NMR) for further structure elucidation. Function-based screening of 5400 clones led to the identification of an operon containing three ORFs encoding acetyltransferase GlcA (ORF1), acyltransferase GlcB (ORF2), and phosphatase/HAD GlcC (ORF3). E. coli pCAT2, with all three ORFs, resulted in the production of identical R. badensis DSM 100043T glucosedilipid with Glu-C10:0-C12:1 as the main congener. ORF2-deletion strain E. coli pAFP1 primarily produced glucosemonolipids, with Glu-C10:0,3OH and Glu-C12:0 as the major congeners, predominantly esterified at the C-2 position of the glucose moiety. Furthermore, fed-batch bioreactor cultivation of E. coli pCAT2 using glucose as the carbon source yielded a maximum glucosedilipid titer of 2.34 g/L after 25 h of fermentation, which is 55-fold higher than that produced by batch cultivation of R. badensis DSM 100043T in the previous study.

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