Lignin removal from teak veneer using combinations of enzymes and hydrogen peroxide

Abstract

The main purpose of this doctoral research is to study the effects of enzymes combination and hydrogen peroxide on lignin removal from commercially grown teak veneer with minimum changing in its natural texture. Controlled laboratory experiments using samples of teak veneer, combinations of xylanase. laccase and hydrogen peroxide, and series of lignin removal time were conducted to accomplish the research purpose. Image processing technique was used to determine lignin removal from pre- and post. treated veneer samples Xylanase, laccase, and hydrogen peroxide concentrations wee varied between 0.01 to 2.50 unit /milliliter, 0.01 to 1.00 unit /milliliter and 2 to 20 % respectively, while the experimental time was conducted between 0.5 to 24 hours. All experiments concerning hydrogen peroxide were performed at 60%C and pH 6.5. The major findings from this research are summarized and presented as follows. Xylanase and laccase do not help removing lignin from teak veneer, in contrast to hydrogen peroxide. However, when using the combination of 0.05 unit /milliliter xylanase and 10% hydrogen peroxide at 60℃ and pH 6.5 for 4 hours, lignin at the amount of 24.34% in gray scale was removed- a 10% improvement over the sole 10% hydrogen peroxide. The mixture of laccase and hydrogen peroxide lower the hydrogen peroxide ability to remove lignin. Moreover, it was found that removal of lignin is best done first by the action of xylanase then follows by hydrogen peroxide or mixtures of hydrogen peroxide and laccase. The best condition for lignin removal form teak veneer is 0.05 unit /milliliter xylanase at 32℃ and pH 4.5 tor thirty minutes follows by the mixture of 10% hydrogen peroxide and 0.05 unit /milliliter laccase at 60℃ and pH 6.5 for 4 hours. This condition results in 26.4% change in gray scale, a 19.3% improvement over the sole 10% hydrogen peroxide.