Comparison of lignin derivatives as substrates for laccase-catalyzed scavenging of oxygen in coatings and films

Kristin Johansson,Leif J Jönsson,Thomas Gillgren,Lars Järnström,Sandra Winestrand

doi:10.1186/1754-1611-8-1

Abstract

BackgroundLignin derivatives are phenylpropanoid biopolymers derived from pulping and biorefinery processes. The possibility to utilize lignin derivatives from different types of processes in advanced enzyme-catalyzed oxygen-scavenging systems intended for active packaging was explored. Laccase-catalyzed oxidation of alkali lignin (LA), hydrolytic lignin (LH), organosolv lignin (LO), and lignosulfonates (LS) was compared using oxygen-scavenging coatings and films in liquid and gas phase systems.ResultsWhen coatings containing lignin derivatives and laccase were immersed in a buffered aqueous solution, the oxygen-scavenging capability increased in the order LO < LH < LA < LS. Experiments with coatings containing laccase and LO, LH or LA incubated in oxygen-containing gas in air-tight chambers and at a relative humidity (RH) of 100% showed that paperboard coated with LO and laccase reduced the oxygen content from 1.0% to 0.4% during a four-day period, which was far better than the results obtained with LA or LH. LO-containing coatings incubated at 92% RH also displayed activity, with a decrease in oxygen from 1.0% to 0.7% during a four-day period. The oxygen scavenging was not related to the content of free phenolic hydroxyl groups, which increased in the order LO < LS < LH < LA. LO and LS were selected for further studies and films containing starch, clay, glycerol, laccase and LO or LS were characterized using gel permeation chromatograpy, dynamic mechanical analysis, and wet stability.ConclusionsThe investigation shows that different lignin derivatives exhibit widely different properties as a part of active coatings and films. Results indicate that LS and LO were most suitable for the application studied and differences between them were attributed to a higher degree of laccase-catalyzed cross-linking of LS than of LO. Inclusion in active-packaging systems offers a new way to utilize some types of lignin derivatives from biorefining processes.

Highlights

Lignin derivatives are phenylpropanoid biopolymers derived from pulping and biorefinery processes
Oxygen scavenging The lignin derivatives LO, LA, LH and LS were evaluated as potential components of oxygen-scavenging coatings containing laccase from the white-rot fungus Trametes versicolor as catalyst
The oxygen-consumption rate of pieces of aluminum foil coated with laccase and different lignin derivatives was determined in buffered aqueous solutions by using an oxygen electrode

Summary

Introduction

Lignin derivatives are phenylpropanoid biopolymers derived from pulping and biorefinery processes. The possibility to utilize lignin derivatives from different types of processes in advanced enzyme-catalyzed oxygen-scavenging systems intended for active packaging was explored. Endeavors to decrease human impact on the climate and the environment include using resources more efficiently, changing from fossil to renewable resources, and processing resources in more efficient ways. Since most plastics are made of petroleum, which is not a renewable resource, our massive use of plastic packages runs contrary to a sustainable development. Lignin is a renewable biopolymer and one of the main components of wood. Whereas the main component of processed wood, cellulose, is used for paper, paperboard, viscose and many other products, lignin often goes to energy recovery [4]. Food degradation processes are most often oxygen dependent, and keeping oxygen from the food is a way of maintaining the quality and increasing the shelf-life of the food

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