Marine-derived chitosan as an antimicrobial biopolymer: properties, mechanisms, applications, and perspectives from Vietnam

Marine-derived chitosan, primarily obtained from crustacean shell by-products, is a biodegradable and biocompatible biopolymer with antimicrobial activity reported against a range of bacteria, yeasts, and filamentous fungi. Growing concerns about food safety, antimicrobial resistance, and sustainable use of seafood-processing waste have increased interest in chitosan-based antimicrobial systems for seafood preservation, packaging, and aquaculture. This narrative critical review evaluates advances in chitosan's physicochemical properties, antimicrobial mechanisms, and material engineering strategies, with emphasis on nanochitosan, composite formulations, and chemically modified derivatives. Particular attention is given to research conducted in Vietnam and to studies in which a marine or crustacean-derived source was explicitly reported. The available evidence indicates that antimicrobial performance depends strongly on molecular weight, degree of deacetylation, pH, target microorganism, and formulation conditions. Nanochitosan and composite systems have shown enhanced antimicrobial activity in several experimental settings, but direct comparisons with native chitosan remain limited because study designs and testing protocols vary substantially. The review identifies important limitations related to raw-material variability, extraction and characterization methods, antimicrobial assays, nanoparticle characterization, scalability, safety assessment, and regulatory requirements. Future research should therefore prioritize standardized characterization and testing, structure–activity relationship analysis, application-specific safety assessment, and scalable processing to support evidence-based development of chitosan-based antimicrobial materials for marine and food-related applications.