Effects of organosolv lignin on the physical and functional properties of polyhydroxyalkanoate films

Abstract

Active biodegradable films that protect food products from deterioration and spoilage attract increasing interest in food packaging applications. This study compares the effects of organosolv lignin incorporation on the physical and functional properties of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) films prepared by blown film extrusion and solution casting. For the blown films, increasing the lignin concentration from 0.5 to 1.0 wt% reduces the mechanical strength, as indicated by decreases in both maximum stress and elongation at break. In addition, lignin incorporation improves the gas and moisture barrier properties of the functional films prepared by both processes. The UV-blocking ability increases with lignin content, with a more pronounced effect in the blown films. Incorporation of lignin by blown film extrusion effectively inhibits the growth of Staphylococcus aureus, Bacillus subtilis, Candida albicans, and Aspergillus niger. In comparison, the solution-cast films prepared by doctor blading show weaker antimicrobial activity against most tested pathogens and exhibit no inhibitory effect against Gram-negative bacteria. Overall, this work demonstrates that organosolv lignin incorporation and processing method strongly influence the barrier, UV-blocking, and antimicrobial properties of polyhydroxyalkanoate-based films, while lignin content affects the mechanical behavior of blown films, highlighting their functional potential for active packaging.

Graphical abstract