Oxygen-scavenging coatings and films based on lignosulfonates and laccase

Laccase and lignosulfonates were included in coating colors and embedded in latex-based or starch-based films and coatings on foil or board. After 6 days at 23 °C and 100% relative humidity, the oxygen content in airtight chambers decreased from 1.0% (synthetic gas consisting of 99% N2 and 1% O2) to 0.3% in the presence of board coated with lignosulfonate and laccase, while the oxygen content remained unchanged in control experiments without enzyme. The water stability of lignosulfonate-containing latex-based coatings and starch-based films was improved after laccase-catalyzed oxidation of lignosulfonates, which indicates polymerization to products with lower solubility in water. Furthermore, the E′ modulus of starch-based films increased with 30%, which indicates laccase-catalyzed polymerization of lignosulfonates resulting in increased stiffness of the film. The results suggest that laccases and lignosulfonates can be used as an oxygen-scavenging system in active packaging and that enzyme-catalyzed polymerization of lignosulfonates contributes to improved water stability and mechanical properties.

► A novel system based on lignosulfonates and laccase was used to create oxygen-scavenging films and paperboard coatings. ► The new system is fundamentally different from previous systems based on glucose oxidase or laccase, since a polymeric substrate was included in the film, rather than a small organic molecule, such as glucose or a monomeric phenol. ► As oxidation by laccase results in cross-linking of lignosulfonates, the properties of the films and coatings change as oxygen scavenging occurs. ► Enzyme-catalyzed cross-linking of lignosulfonates resulted in improved water stability and mechanical properties.