Chitosan production from agro-wastes by Aspergillus tubingensis: A sustainable approach for beef burger quality improvement

Abstract Background Chitosan is commonly obtained by deacetylation of chitin from crustacean shell wastes such as shrimp and crab, but unfortunately, these sources appear limited for their unavailability. So, an alternative abundant chitin source is in need as fungi mycelia. Results In this study, chitosan production through submerged (SMF) and solid-state fermentation (SSF) of Aspergillus tubingensis utilizing various agro-wastes and by-products like whey, blackstrap molasses, beet waste, rice (husk& straw), wheat bran and sawdust as a sole carbon source was investigated. The best waste was beet waste (33.12% and 38.61% of chitin and chitosan yields for SSF and whey (whey (24.22% and 35.90% of chitin and chitosan yields) for SmF, as compared to the control of sucrose (17.11% and 20.38% of chitin and chitosan yields) after 8–12 and 8 days of incubation, respectively. The fungal polymer had antibacterial activity against Staphylococcus aureus DSMZ20231, Salmonella Typhimurium ATCC14028, Bacillus cereus DSMZ345, Pseudomonas fluorescens NRRL800, and Escherichia coli ATCC69373 at a significant concentration of 1.0% were assayed using Kirby-Bauer disc diffusion method. Staph. aureus DSMZ20231& S. Typhimurium ATCC14028 were more susceptible to chitosan, which gave the largest zone inhibition of 47 and 43 mm, respectively. Moreover, the polymer's antibacterial activity was tested in the broth medium during different incubation periods (12-48h). results indicated that all tested pathogenic strains exhibited complete inhibition after 24 h incubation except B. cereus DSMZ345 was the most stable up to 48h. Application of fungal chitosan (1.0%) for a laboratory-manufactured beef burger led to improve quality analysis of the texture, physical or technological and chemical properties than control without chitosan. At the same time, beef burger supplemented with chitosan was significantly accepted overall by the panelist than the control. Therefore, fungal chitosan extended the beef burger's shelf life and maintained its quality indices during freezing storage. Conclusions Fungal chitosan is a beneficial natural antimicrobial, and applying it to beef burgers improves microbiological, technological, and chemical quality while also extending shelf life by up to 8 weeks, making it a viable alternative to chemical protective additives. Future research on this fungal chitosan will focus on large-scale meat or poultry preservation or additive applications.