57 research outputs found
Production, characterisation, and application of Beauveria bassiana SAN01 β-glucosidase
No full textSubmitted in fulfilment for the Degree of Master of Applied Science in Biotechnology, Durban University of Technology, Durban, South Africa, 2025.Beauveria bassiana is a popular entomopathogenic fungal endophyte that is used industrially
as a biocontrol agent. It has been noted to be non-pathogenic to humans, animals and plants
and their ability to utilise various agro-residues for its metabolism has been exploited for the
production of some lignocellulosic enzymes. Previous studies have mostly focused on the
production of key lignocellullose hydrolysing enzymes, however, little is known about the
ability of B. bassiana to produce accessory enzymes such as β-glucosidase which also aid in
lignocellullose breakdown. Hence, this study was aimed at investigating the production, the
biochemical characteristics, and the potential application of a β-glucosidase from the strain
designated as Beauveria bassiana SAN01. For these aims to be achieved, the production
parameters of β-glucosidase were optimised using a statistical approach. Furthermore, to
enhance the evaluation of the biochemical properties and potential industrial application of the
enzyme, it was purified to homogeneity using salt precipitation, and chromatography.
The preliminary screening of seven agricultural residues showed that the haulm of Bambara an underutilised African legume- supported the highest β-glucosidase production, hence,
statistical optimisation of enzyme production was performed using this biomass as the sole
carbon source. The three-level statistical optimisation experiments resulted in a ~5.36-fold
increase in β-glucosidase production from the unoptimised level of 132.71 U/mL to 711 U/mL,
under optimal conditions (Bambara - 57 g/L, KCl - 302 mg/L, NaCl -154 mg/L, agitation -150
rpm, and incubation time - 223 h). Ammonium sulphate precipitation followed by dialysis and
gel filtration chromatography were used to purify β-glucosidase produced by B. bassiana
SAN01 to homogeneity. The purified β-glucosidase was demonstrated to have a specific
activity of 496 U/mg and a molecular mass of ~116 kDa by SDS-PAGE; its activity pattern
was also confirmed via in-gel zymography using 4-methylumbelliferyl-β-D-glucopyranoside
as the substrate. The enzyme activity was recorded to be optimal at pH 5.0 and 60°C and the
enzyme also displayed significant thermal stability from temperatures 30-50°C, retaining
almost 60% of its activity at 50°C after 4 h of incubation. Subsequently, the potential of B.
bassiana SAN01 β-glucosidase as an accessory enzyme in lignocellulose saccharification was
demonstrated by its effectiveness in the hydrolysis of cellobiose converting more than 90% of
the substrate to glucose. Finally, some structural insights were gained into the enzyme using a
computational approach. The in silico prediction of the enzyme revealed that it has an
isoelectric point of 5.59, that it was hydrophilic and thermostable. The modelled 3D structure
of B. bassiana β-glucosidase confirmed that it belongs to the GH 1 family and the model was validated by the presence of ~ 96% of its amino acid residues in the favoured region of the
Ramachandran plot. The docking of the enzyme with cellobiose and 4-nitrophenol β-D glucopyranoside demonstrated the significant affinity of both substrates to the enzyme while
revealing its most probable active site. Results from this study demonstrate B. bassiana as a
hyper-producer of β-glucosidase as the production level in this study is one of the highest ever
recorded for an entomopathogenic fungi; thus the study highlights the immense potential of
B. bassiana in the processing of lignocellulosic biomass to biofuels.National Research Foundation (NRF)
Biochemical characterization of selected carbohydrases from Beauveria bassiana and their potential applications
No full textSubmitted in fulfilment of the requirements for the degree of Doctor of Philosophy (PhD): Biotechnology, Durban University of Technology, Durban, South Africa, 2021.Different filamentous fungi have continued to attract scientific interests as novel sources of enzymes and other important bioproducts. Beauveria bassiana, a well-known entomopathogenic fungi has long been valued for its biotechnological application as a biocontrol agent in its entomopathogenic state and as a plant-growth promoter in its endophytic state. The fungus has also been proven to be safe for human health, as studies have shown B. bassiana strains to be non-pathogenic to humans, other animals and plants. Furthermore, its ability to utilize various agro-residues for its growth and the concomitant production of important bioproducts have been well demonstrated. However, despite all of these, there has been no appreciable attempt at exploring this remarkable fungus for the production of industrially important enzymes, especially in its saprophytic state. Recently, a filamentous fungus was isolated in its endophytic state from onion leaves, in our laboratory. It was confirmed by rDNA ITS sequencing to be a B. bassiana strain and was subsequently designated as B. bassiana SAN01. Preliminary experiments revealed the remarkable ability of this novel strain to utilize lignocellulosic biomass for its metabolism while secreting various biomass-degrading enzymes in the process. Hence, carbohydrases from B. bassiana SAN01 were considered worthy of investigation because of the established safety of the source organism, as well as the probable low production cost of the enzymes using readily available plant biomass. Besides, it was also observed that there has been no significant investigation into the biochemical properties of lignocellulolytic enzymes from B. bassiana, which has probably hindered their industrial applicability.
Hence, this Ph.D. research was focused on investigating the production, the biochemical properties, as well as the potential applicability of selected biomass-degrading enzymes, viz., amylase, cellulase (endoglucanase), pectinase (polygalacturonase) and xylanase from B. bassiana SAN01. To achieve these, the phylogenetic relationship of the fungal strain was established, and its carbon utilization profile was annotated using phenotypic microarray technology. Furthermore, to understand the dynamics surrounding its lignocellulosic biomass utilization and its carbohydrase-production capabilities, comparative transcriptomics analysis was carried out B. bassiana SAN01 under three different simulated conditions i.e., endophytic, fermentation and lab control conditions. In addition, to fully explore the carbohydrase production potential of the fungus, the production of the selected carbohydrases was optimized using response surface methodology; subsequently, all the selected enzymes were purified to enhance the evaluation of their biochemical properties as well as their potential industrial applications.
The proclivity of B. bassiana SAN01 for polyols, pentoses, N-acetyl-D-glucosamine and some other carbon sources was demonstrated by the phenotype microarray profiling. While the comparative genome-wide transcriptome analyses revealed a clear distinction between the fungus under the different trophic conditions investigated. It was observed that 4-5% of the 10,365 B. bassiana SAN01 genes were differentially expressed between these conditions, and a significant proportion of the genes were found to be involved in lignocellulose deconstruction. The annotation of CAZymes from the B. bassiana SAN01 transcriptome under fermentation (saprophytic) conditions confirmed the upregulation of biomass-degrading enzymes such as amylases, cellulases, chitinases, glucanases, laccases, lignases, pectinases and xylanases. The subsequent optimization of the production parameters of B. bassiana SAN01 amylase, endoglucanase, polygalacturonase and xylanase led to heightened yields of 34.82 UmL-1, 23.03 UmL-1, 51.05 UmL-1, and 1061 UmL-1, respectively. These were estimated to be 1.79-, 1.35-, 1.87- and 3.44- folds higher than unoptimized production levels and are also the highest ever production levels recorded for these enzymes from any B. bassiana strain.
Further in the study, the xylanase from B. bassiana SAN01 was purified to homogeneity while the other three enzymes were partially purified. The purified xylanase was demonstrated to have a molecular mass of ~37 kDa and performed optimally at pH 6.0 and 45oC. However, the optimum pH of the partially purified amylase, endoglucanase, and polygalacturonase were found to be pHs 6.0, 6.0 and 7.0, while the optimum temperatures were observed to be 35oC, 35oC and 45oC, respectively. Consequently, the purified B. bassiana SAN01 xylanase was demonstrated to be effective in deinking wastepaper with an optimized deinking rate of 106.72% relative to the control. In addition, the partially purified amylase-polygalacturonase from B. bassiana SAN01 was demonstrated to adequately clarify pear juice with a 1.37-fold improvement in clarity recorded under optimal conditions. Furthermore, results also showed that the enzymatic- assisted juice clarification was without any detrimental effect on some quality parameters of the juice. In the same vein, crude endoglucanase-xylanase from the fungus was shown to significantly hydrolyze sugarcane bagasse, releasing ~20% reducing sugars under optimal conditions. Finally, to gain insights into the structure-function relationship of B. bassiana carbohydrases, the structural properties of B. bassiana chitinases and xylanases were elucidated for the first time using computational techniques. The in silico prediction revealed that the enzymes were generally hydrophilic, thermostable, negatively charged and extracellularly secreted. The modelled tertiary structures of B. bassiana chitinase and xylanase were validated by the presence of ~ 90% of their amino acid residues in the Ramachandran plot’s favoured region. The findings from this study have thus created a strong framework for the prospective utilization of B. bassiana and its carbohydrases in alternative biotechnological processes.
Diversity, stability and applications of mycopigments
No full textThe role of fungi as major pigment producers in the environments has endeared their application as sources of industrially important pigments. Compared to synthetic colorants, fungal pigments are rapidly becoming the preferred choice due to their biodegradability, eco-friendliness and versatility. Besides their uses as colourants, their functions as preservatives and/or bioactive agents have promoted their potential across numerous industries. In the past, more focus has been placed on enhancing the production levels of fungal pigments with little attention to the stabilization of the pigments and other important areas of concern. To this end, this review draws attention to the diverse classes of fungal pigments with emphasis on their existing and future applications, especially in the food and textile industries. Emphasis was also placed on the factors affecting fungal pigment stability and the techniques to efficiently circumvent the instability. Finally, the application of emerging technologies such as copigmentation, microencapsulation, metabolic engineering, and chemo-informatics tools in enhancing the mycopigment industry are highlighted
Retraction notice to “MPPT efficiency enhancement of a grid connected solar PV system using Finite Control set model predictive controller” [Heliyon 10 (2024) e27663]
No full textThis article has been retracted: please see Elsevier policy on article withdrawal (https://www.elsevier.com/about/policies-and-standards/article-withdrawal).This article has been retracted at the request of the Editor-In-Chief.An investigation conducted on behalf of the journal by Elsevier's Research Integrity & Publishing Ethics team found a significant increase of citations to papers published by the author, Ayodeji Olalekan Salau, between the original submission and the revised version of this article. In summary, zero papers by the author were cited in the original version of the article. This increased to ten papers in the revised version of the article. The investigation also found phrases that make some passages in the article difficult to parse. The authors were requested to explain the use of these passages of text but were unable to do so. The Editor has lost confidence in the findings of the article and has determined that it should be retracted.The authors disagree with the retraction and dispute the grounds for it
Sustainable polyhydroxyalkanoates in the bioeconomy: a review of recent advances in production innovations, economic feasibility, and patents landscape /
No full textIn light of the global environmental crisis caused by traditional plastics and their pollution, there is an urgent need for sustainable alternatives to plastics derived from fossil fuels. Polyhydroxyalkanoates (PHA) is a microbial intracellular energy reserve with the potential to replace petroleum-based plastics and reduce environmental pollution. PHA exhibits mechanical and thermal properties comparable to petroplastics, with the added advantages of biodegradability and biocompatibility. Furthermore, their physicochemical versatility makes them suitable for a wide range of applications, including eco-friendly packaging, agricultural mulch films, and innovative medical devices. However, large-scale PHA adoption remains constrained by production costs, as well as by challenges in scalability, feedstock supply, and downstream extraction, which all culminate in an uncompetitive minimum selling price (MSP) estimated at $4-8/kg. Considering the aforementioned, this review aimed to provide a comprehensive evaluation of strategies for enhancing PHA production efficiency within a circular bioeconomy framework. It examines intrinsically diverse microbial communities that produce PHA, fermentation strategies, feedstock diversification, and green recovery techniques. It also evaluated emerging application trends and industrial potential, focusing on more than 20 PHA-related patents filed between 2020 and 2025. Finally, this study examined the economic feasibility of PHA production and identified feasible pathways toward more cost-competitive adoption of the biopolymer
Writing a Scientific Review Article: Comprehensive Insights for Beginners
No full textReview articles present comprehensive overview of relevant literature on specific themes and synthesise the studies related to these themes, with the aim of strengthening the foundation of knowledge and facilitating theory development. The significance of review articles in science is immeasurable as both students and researchers rely on these articles as the starting point for their research. Interestingly, many postgraduate students are expected to write review articles for journal publications as a way of demonstrating their ability to contribute to new knowledge in their respective fields. However, there is no comprehensive instructional framework to guide them on how to analyse and synthesise the literature in their niches into publishable review articles. The dearth of ample guidance or explicit training results in students having to learn all by themselves, usually by trial and error, which often leads to high rejection rates from publishing houses. Therefore, this article seeks to identify these challenges from a beginner’s perspective and strives to plug the identified gaps and discrepancies. Thus, the purpose of this paper is to serve as a systematic guide for emerging scientists and to summarise the most important information on how to write and structure a publishable review article
Fungal mycelium as leather alternative: A sustainable biogenic material for the fashion industry
No full textThe global leather industry has been at the receiving end of various environmental and ethical backlash as it mainly relies on animal agriculture which contributes to deforestation, greenhouse gas emissions, and animal welfare concerns. In addition, the processing of animal hides into leather generates a huge amount of toxic chemicals, which ultimately get released into the environment. Thus, growing concern for environmental sustainability has led to the exploration of alternative materials to conventional animal- based leather. In this regard, the application of fungal leather alternatives in material technology is gaining traction because of its high biodegradability, biocompatibility, renewability, as well as its affordable and carbon-neutral growth processes. Fungal leather alternatives have been found to possess significant mechanical and physical properties, thanks to the interwoven hyphal network of the fungal mycelium, as well as antimicrobial activities which have been ascribed to their bioactive metabolites. Various fungal species, including those from the Agaricus, Fomes, Ganoderma, Phellinus, and Pleutorus genera, are currently being investigated for their potential in this area. This review, therefore, attempts to gain insights into the recent advances in scientific research and real-world applications of fungal-derived leather like materials. It makes a compelling case for this sustainable alternative and discusses the morphology-property relationship of the fungal mycelium driving this innovation. Additionally, the current processing methods and major players in the fungal leather substitute industry are presented. The paper also brings attention to the challenges facing the full deployment of fungal leather substitutes and proposes solutions with the aim of encouraging further research and resource mobilization for the acceptance of this renewable leather substitute
Biochemical and in silico structural properties of a thermo-acid stable β-glucosidase from Beauveria bassiana
No full textβ-glucosidase hydrolyses the glycosidic bonds in cellobiose and cello-oligosaccharides, a critical step in the saccharification for biofuel production. Hence, the aim of this study was to gain insights into the biochemical and structural properties of a β-glucosidase from Beauveria bassiana, an entomopathogenic fungus. The β-glucosidase was purified to homogeneity using salt precipitation, ultrafiltration, and chromatographic techniques, attaining a specific activity of 496 U/mg. The molecular mass of the enzyme was then estimated via SDS-PAGE to be 116 kDa, while its activity pattern was confirmed by zymography using 4-methylumbelliferyl-β-d-glucopyranoside. Furthermore, the pH optima and temperature of the enzyme were found to be pH 5.0 and 60 °C respectively; its activity was significantly enhanced by Mg2+ and Na+ and was found to be relatively moderate in the presence of ethanol and dichloromethane. Molecular docking of the modelled B. bassiana β-glucosidase structure with the substrates, viz., 4-nitrophenyl β-d-glucopyranoside and cellobiose, revealed the binding affinity energies of −7.2 and −6.2 (kcal mol−1), respectively. Furthermore, the computational study predicted Lys-657, Asp-658, and Arg-1000 as the core amino acid residues in the catalytic site of the enzyme. This is the first investigation into a purified β-glucosidase from B. bassiana, providing valuable insights into the functional properties of carbohydrases from entomopathogenic fungal endophytes
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