Abstract
Despite being widely available, Saccharomyces cerevisiae has not been widely explored for direct extraction of chitosan biopolymer for antimicrobial applications. In our study, S. cerevisiae from Baker's yeast and Aspergillus niger from moldy onion extracts are studied as alternative sources of chitosan; and S cerevisiae chitosan tested for antimicrobial efficacy. The properties of S. cerevisiae chitosan are compared with moldy onion chitosan and shrimp chitosan extracted from shrimp shells. Chitosan extracted from S. cerevisiae is tested for antimicrobial efficacy against Staphylococcus Aureus. The maximum yields of fungal chitosan are 20.85 ± 0.35mg/g dry S. cerevisiae biomass at 4th day using a culture broth containing sodium acetate, and 16.15 ± 0.95mg/g dry A. niger biomass at 12th day. The degree of deacetylation (DD%) of the extracted fungal chitosan samples from S. cerevisiae and A. niger is found to be 63.4%, and 61.2% respectively, using Fourier Transform Infrared Spectroscopy. At a concentration of 2g/L, S. cerevisiae chitosan shows the maximum inhibition zone diameter of 15.48 ± 0.07mm. Baker's yeast S cerevisiae biomass and A. niger from moldy onions has not been previously explored as a source of extractible fungal chitosan. This study gives insight that S. cerevisiae and A. niger from agricultural or industrial wastes could be a potential biomass source for production of the chitosan biopolymer. The S. cerevisiae chitosan displayed effective antimicrobial properties against S aureus, indicating the viablitiy of S cerevisae as a resource for extraction of high-quality chitosan.
Highlights
Chitin and chitosan are valuable biopolymers found in biomass resources
Numerous fungal species from the class Zygomycetes such as Aspergillus, Rhizopus, Absidia, Gongronella have been studied for chitosan extraction. [14][16][17] Chitosan is synthesized in the spores of Saccharomyces cerevisiae which is a type of unicellular fungi
This indicated with certainty that the species isolated from moldy onions belonged to Aspergillus niger and these were taken for further processing for isolation of fungal chitosan
Summary
Chitin and chitosan are valuable biopolymers found in biomass resources. Removal of acetyl groups from a percentage of the N-acetyl-D-glucosamine units in chitin chains leads to formation of chitosan, and if the copolymer has higher than 50-60% D-glucosamine it is categorized as chitosan.[1] [2] (Fig 1). The polycationic nature of chitosan, high charge density, and presence of free amine groups in the chain enables it to go through chemical and enzymatic modifications as well as crosslinking.[3][4] chitosan has its applicability in diverse areas. It is used in biomedical field such as drug delivery, gene transport, wound healing, stem cell technology and tissue engineering due to its exceptional biocompatibility and antimicrobial activity.[5]-[6] Chitosan is a biodegradable polymer, and used in agricultural sectors as well as pharmaceutical, food and in some fields of biotechnology such as enzyme immobilization,[7] and in environmental applications in water treatment plants as flocculent or to remove metal ions from wastewater. Chitin obtained from crustacean shells are the major source of industrial chitosan production. Numerous fungal species from the class Zygomycetes such as Aspergillus, Rhizopus, Absidia, Gongronella have been studied for chitosan extraction. [14][16][17] Chitosan is synthesized in the spores of Saccharomyces cerevisiae ( known as baker’s yeast) which is a type of unicellular fungi
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