Enabling chitosan antimicrobial activity in melt-processed PLA blends through pre-blending with PVA

Chitosan is a bio-based polymer of interest for packaging, coatings, biomedical devices, and healthcare materials owing to its biodegradability, biocompatibility, and intrinsic antimicrobial activity. However, achieving antimicrobial activity in melt-processed polyester materials containing chitosan remains challenging, because chitosan is not readily melt-processable under conventional conditions and its high polarity often leads to poor interfacial adhesion and coarse dispersion. In the present work, antimicrobial poly(lactic acid) (PLA) blends containing chitosan were obtained through a previously reported route. Briefly, poly(vinyl alcohol)/chitosan (PVA-Chitosan) mixtures were first prepared in solution, dried either by oven-drying or freeze-drying, and subsequently melt-blended with poly(lactic acid) by extrusion, thus incorporating chitosan as a dispersed blend phase rather than as a conventional filler. Antimicrobial assays against Escherichia coli and Staphylococcus aureus showed activity only at 6.5 wt % chitosan, with a stronger effect for blends prepared from the freeze-dried precursor, which exhibited a smaller and more homogeneous dispersed phase. These findings show that the antimicrobial activity of PLA/PVA-chitosan blends depends not only on chitosan content but also on the homogeneity of the chitosan-containing dispersed phase and demonstrate that pre-blending with PVA is an effective route to enable antimicrobial function in melt-processed blends.