Fungal chitosan in focus: a comprehensive review on extraction methods and applications

Increasing awareness of the adverse effects of nonrenewable, petroleum-based synthetic plastics has driven the search for biodegradable alternatives, particularly in food packaging. Over the past 30 years, biopolymeric materials, such as chitosan, have attracted considerable attention owing to their reduced environmental impact. Chitosan, which is derived from the partial deacetylation of chitin, is valued for its abundance, non-toxicity, biodegradability, and antimicrobial properties, making it a promising candidate for the development of biocomposites. Although chitin is typically sourced from crustacean shells, fungal sources offer notable advantages, including lower mineral content and a continuous, high-quality supply without seasonal variations. Moreover, amid increasing evidence of microplastic-induced toxicity in aquatic organisms and mammals, the risk of contamination in marine-derived chitosan highlights the need for safer alternatives such as fungal sources. This review discusses the physicochemical properties of fungal chitosan and explores advanced extraction techniques such as deep eutectic solvents, microwave-assisted extraction, and enzymatic extraction. Additionally, the antimicrobial potential of fungal chitosan is thoroughly examined, underscoring its potential in food packaging, biomedical, and pharmaceutical applications. The effects of the degree of deacetylation, solubility, and molecular weight of chitosan on its physicochemical and biological properties are highlighted, facilitating its optimization for diverse applications.