Saccharomyces Cerevisiae as an Untapped Source of Fungal Chitosan for Antimicrobial Action

Chitosan-Based Gel Development: Extraction, Gelation Mechanisms, and Biomedical Applications

Chitosan (CS), a versatile biopolymer obtained through the deacetylation of chitin, has gained significant interest in biomedical and pharmaceutical applications due to its biocompatibility, biodegradability, and unique gel-forming capabilities. This review comprehensively analyzes CS-based gel development, covering its extraction from various natural sources, gelation mechanisms, and biomedical applications. Different extraction methods, including chemical, biological, and green techniques, are discussed regarding efficiency and sustainability. The review explores the physicochemical properties of CS that influence its gelation behavior, highlighting various gelation mechanisms such as physical, ionic, and chemical cross-linking. Recent advances in gel formation, including Schiff base reactions, Diels-Alder click chemistry, and thermosensitive gelation, have expanded the applicability of CS hydrogels. Furthermore, CS-based gels have demonstrated potential in wound healing, tissue engineering, drug delivery, and antimicrobial applications, offering controlled drug release, enhanced biocompatibility, and tunable mechanical properties. The incorporation of nanomaterials, bioactive molecules, and functional cross-linkers has further improved hydrogel performance. The current review underscores the growing significance of CS-based gels as innovative biomaterials in regenerative medicine and pharmaceutical sciences.

BTS1-knockout Saccharomyces cerevisiae with broad-spectrum antimicrobial activity through lactic acid accumulation

Bacterial infections pose significant threats to human health, and prudent antibiotic use remains a key strategy for disease treatment and control. However, a global escalation of drug resistance among pathogenic bacteria presents a formidable challenge. Probiotics have emerged as a promising approach to combating pathogenic bacterial infections. In this study, we investigated the antibacterial activity of BTS1-knockout (BTS1-KO) Saccharomyces cerevisiae. Our findings demonstrate its effective inhibition of pathogen growth as evidenced by Minimum inhibitory concentration (MIC) assays, growth curves, bacteriostatic spectrum analyses and co-culture experiments. Additionally, it significantly impedes Escherichia coli and Staphylococcus aureus biofilm formation. Moreover, BTS1-KO S. cerevisiae exhibits low haemolytic activity, acid resistance, resistance to high bile salt concentrations, high auto-aggregation capacity and high co-aggregation capacities with pathogenic bacteria. Moreover, infected larvae treated with BTS1-KO S. cerevisiae in Galleria mellonella-E. coli (in vivo) and G. mellonella-S. aureus (in vivo) infection models showed significantly prolonged survival times. Mechanistic investigations revealed that BTS1-KO S. cerevisiae primarily produced lactic acid via metabolism, thereby lowering the environmental pH and inhibiting pathogenic bacterial growth. In summary, our study underscores the probiotic potential of BTS1-KO S. cerevisiae, offering broad-spectrum antibacterial activity in vitro and in vivo with low toxicity. This highlights BTS1-KO S. cerevisiae as a promising probiotic candidate for clinical prevention and control of bacterial infection.

A structure-functionality insight into the bioactivity of microbial polysaccharides toward biomedical applications: A review

Microbial polysaccharides (MPs) are biopolymers secreted by microorganisms such as bacteria and fungi during their metabolic processes. Compared to polysaccharides derived from plants and animals, MPs have advantages such as wide sources, high production efficiency, and less susceptibility to natural environmental influences. The most attractive feature of MPs lies in their diverse biological activities, such as antioxidative, anti-tumor, antibacterial, and immunomodulatory activities, which have demonstrated immense potential for applications in functional foods, cosmetics, and biomedicine. These bioactivities are precisely regulated by their sophisticated molecular structure. However, the mechanisms underlying this precise regulation are not yet fully understood and continue to evolve. This article presents a comprehensive review of the most representative species of MPs, including their fermentation and purification processes and their biomedical applications in recent years. In particular, this work presents an in-depth analysis into the structure-activity relationships of MPs across multiple molecular levels. Additionally, this review discusses the challenges and prospects of investigating the structure-activity relationships, providing valuable insights into the broad and high-value utilization of MPs.

Fighting Emerging Caspofungin-Resistant Candida Species: Mitigating Fks1-Mediated Resistance and Enhancing Caspofungin Efficacy by Chitosan

Invasive candidiasis poses a worldwide threat because of the rising prevalence of antifungal resistance, resulting in higher rates of morbidity and mortality. Additionally, Candida species, which are opportunistic infections, have significant medical and economic consequences for immunocompromised individuals. This study explores the antifungal potential of chitosan to mitigate caspofungin resistance in caspofungin-resistant Candida albicans, C. krusei, and C. tropicalis isolates originating from human and animal sources using agar well diffusion, broth microdilution tests, and transmission electron microscope (TEM) analysis of treated Candida cells. Reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) was performed to assess the expression of SAGA complex genes (GCN5 and ADA2) and the caspofungin resistance gene (FKS) in Candida species isolates after chitosan treatment. The highest resistance rate was observed to ketoconazole (80%) followed by clotrimazole (62.7%), fluconazole (60%), terbinafine (58%), itraconazole (57%), miconazole (54.2%), amphotericin B (51.4%), voriconazole (34.28%), and caspofungin (25.7%). Nine unique FKS mutations were detected, including S645P (n = 3 isolates), S645F, L644F, S645Y, L688M, E663G, and F641S (one isolate in each). The caspofungin minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) values before chitosan treatment ranged from 2 to 8 µg/mL and 4 to 16 µg/mL, respectively. However, the MIC and MFC values were decreased after chitosan treatment (0.0625-1 µg/mL) and (0.125-2 µg/mL), respectively. Caspofungin MIC was significantly decreased (p = 0.0007) threefold following chitosan treatment compared with the MIC values before treatment. TEM analysis revealed that 0.5% chitosan disrupted the integrity of the cell surface, causing irregular morphologies and obvious aberrant changes in cell wall thickness in caspofungin-resistant and sensitive Candida isolates. The cell wall thickness of untreated isolates was 0.145 μm in caspofungin-resistant isolate and 0.125 μm in sensitive isolate, while it was significantly lower in chitosan-treated isolates, ranging from 0.05 to 0.08 μm when compared with the cell wall thickness of sensitive isolate (0.03 to 0.06 μm). Moreover, RT-qPCR demonstrated a significant (p < 0.05) decrease in the expression levels of histone acetyltransferase genes (GCN5 and ADA2) and FKS gene of caspofungin-resistant Candida species isolates treated with 0.5% chitosan when compared with before treatment (fold change values ranged from 0.001 to 0.0473 for GCN5, 1.028 to 4.856 for ADA2, and 2.713 to 12.38 for FKS gene). A comparison of the expression levels of cell wall-related genes (ADA2 and GCN5) between caspofungin-resistant and -sensitive isolates demonstrated a significant decrease following chitosan treatment (p < 0.001). The antifungal potential of chitosan enhances the efficacy of caspofungin against various caspofungin-resistant Candida species isolates and prevents the development of further antifungal resistance. The results of this study contribute to the progress in repurposing caspofungin and inform a development strategy to enhance its efficacy, appropriate antifungal activity against Candida species, and mitigate resistance. Consequently, chitosan could be used in combination with caspofungin for the treatment of candidiasis.

Mixed organic and inorganic nitrogen sources enhance chitosan yield in novel isolates of Penicillium

Chitosan, a valuable biopolymer, has traditionally been derived from marine sources. However, exploring fungal alternatives offers a sustainable supply. This research investigates the potential of chitosan production from fungal sources, focusing on the optimization of abiotic factors using two novel Penicillium strains (IITISM-ANK1 and IITISM-ANK2) isolated from dry aged sludge. Box-Behnken model and standard statistical analysis were deployed to develop an equation predicting the effect of carbon and nitrogen sources, pH, and temperature on chitosan production. Batch experiments validate the model's accuracy under optimized conditions. The results indicate that mixed organic and inorganic nitrogen sources in the form of peptone, nitrate, and ammonium salts enhanced chitosan yield in both isolates. At optimal conditions for the chitosan production of IITISM-ANK2 and IITISM-ANK1 were found to be 293.29 mg/L and 325.01 mg/L, with the degree of deacetylation of over 74 % which is a critical parameter for chitosan quality. Thus, these isolates can be used as a potent microbe for industrial chitosan production and contribute to advancing sustainable chitosan production and its potential industrial applications.

Low molecular weight chitosan oligosaccharides form stable complexes with human lactoferrin

Proteins in tears, including human lactoferrin (HLF), can be deposited and denatured on contact lenses, increasing the risk of microbial cell attachment to the lens and ocular complications. The surfactants currently used in commercial contact lens care solutions have low clearance ability for tear proteins. Chitosan oligosaccharide (COS) binds to a variety of proteins and has potential for use in protein removal, especially in contact lens care solutions. Here, we analyzed the interaction mechanism of COSs hydrolyzed from chitosan from different resources with HLF. The molecular weights (MWs) and concentrations of COSs were key factors for the formation of COS-HLF complexes. Lower MWs of COSs could form more stable COS-HLF complexes. COS from Aspergillus ochraceus had a superior effect on HLF compared with COS from shrimp and crab shell with the same MWs. In conclusion, COSs could bind to and cause a conformational change in HLF. Therefore, COSs, especially those with low MWs, have potential as deproteinizing agents in contact lens care solution.

Banana peels as a cost effective substrate for fungal chitosan synthesis: optimisation and characterisation

Massive accumulation of unprocessed banana peels enthralls sustainable issues as they are eventually dumped as landfills leading to emission of obnoxious gasses. To avoid these persisting challenges the present study shims lights on chitosan production from the characterised fungal strain using banana peel hydrolysate as an effective medium. Substantial amount of carbohydrate in banana peels serves as a potential solution for fungal chitosan production in a view to attain a circular bioeconomy and repurposed for synthesis of beneficial products in a cost effective manner. Presence of fermentable sugars in banana peels qualifies them as a feasible substrate which could be exploited for scaling up of fungal chitosan synthesis. Screened isolate was subjected to statistical optimisation using formulated medium to elucidate the influential factors that had significant effect on chitosan production. The harvested chitosan biomass was characterised through standardised techniques and evaluated for further studies. Statistical optimisation reveals that ammonium nitrate (5 g/L), pH (6) and incubation time (144 hrs) were the three PBD variables that had a greater influence on fungal chitosan yield. The validated developed model exhibited maximum yield of 200 mg/L, a 4.4 fold increase than unoptimised medium (45 mg/L). These findings emphasise the fermentative synthesis of chitosan through valorisation of banana peel prop up a complementary approach in concomitant with preserving renewable resources and bioproduct formation.

Research Progress on Antibacterial Coatings for Preventing Implant-Related Infection in Fractures: A Literature Review

Implant-related infection is a difficult problem in orthopaedics as it not only leads to failure in internal fixation, but also increases the financial burden and perioperative risk on patients. In the past, orthopaedic implants were designed as mechanical fixation devices simply to maintain mechanical and biological properties, not to regulate the surrounding biological microenvironment. More recently, antimicrobial biocoatings have been incorporated into orthopaedic implants to prevent and treat implant-related infections through the modulation of the local environment. This article reviews the application of orthopaedic-implant biocoating in the prevention of implant-caused infection. Although there are many candidate coatings, they are still in the preclinical testing stage, and thus additional research by biomaterials and clinicians is necessary to identify the ideal implant coatings for patients who require fracture surgery.