Use of Loligo opalescens chitosan-based coatings to inhibit multispecies biofilms in Poly(Lactic Acid)-based packaging

The extensive use of petroleum-based plastics and microbial contamination in food packaging raise health, environmental, and economic issues, increasing the need for sustainable antimicrobial packaging solutions. Chitosan, a polysaccharide obtained by deacetylation of chitin, has remarkable properties, including non-toxicity, biodegradability, good film-forming properties, and antimicrobial activity. This study aimed to produce and characterize Poly(lactic acid) (PLA) films coated with chitosan (PLA-Ch) extracted from Loligo opalescens pens and its depolymerized derivatives of different molecular weights, and to evaluate their antimicrobial activity against dual-species biofilms of Escherichia coli and Pseudomonas putida for 24 h under refrigeration. Chitosan-based surfaces reduced the number of total, viable, and culturable biofilm cells by up to 63 %, 74 %, and 76 %, respectively, compared to uncoated PLA films, regardless of chitosan molecular weight. Confocal laser scanning microscopy validated the inhibitory effect of chitosan-based surfaces on biofilm formation, showing an average reduction of 33 % in biovolume and 43 % in thickness. Additionally, a 64 % decrease in early bacterial adhesion confirmed their anti-adhesive properties. These effects are attributed to chitosan’s surface hydrophilicity and its electrostatic interactions with bacterial membranes. Overall, PLA films coated with chitosan demonstrate strong potential as sustainable antimicrobial materials for food packaging, while simultaneously promoting the valorization of marine industry by-products.