Immobilization of Lysozyme on Food Contact Polymers as Potential Antimicrobial Films

Abstract

The objective of this work was to investigate the feasibility of incorporating an antimicrobial enzyme (lysozyme) into polymers which are suitable for food contact. Hen egg white lysozyme was immobilized on polyvinyl alcohol (PVOH) beads, nylon, 6,6 pellets and cellulose triacetate (CTA) films. Polyvinyl alcohol and nylon 6,6 yielded low activity against a suspension of dried Micrococcus lysodeikticus cells, while CTA yielded the highest activity; 1.25 cm2/ml (CTA film area to substrate volume ratio) fully hydrolyzed a 0.015% (w/v) suspension of dried cells in 30 min. The activity retention of lysozyme immobilized on CTA was 90% after one use and 60% after 20 repeated uses. The amount of enzyme added to the film during immobilization affected the activity of the immobilized lysozyme; highest activities were obtained when CTA films were formed by adding 150–250 mg lysozyme per g polymer. No significant effect of CTA film thickness on lysozyme activity was observed. Viability of M. lysodeikticus grown on tripticase soy broth (TSB) at 30°C was decreased in the presence of CTA film containing lysozyme. The film (0.01 cm2/ml TSB) was inhibitory and bactericidal against 103 and 108 c.f.u./ml M. lysodeikticus respectively. © 1997 John Wiley & Sons, Ltd.