Studies On Lignin Selective Degradation In Bamboo Substrate By White-rot Fungus

Bamboo fiber can be utilized in pulping, paper-making and spinning. The method of delignification is the key technology of bamboo fiber preparation.In this paper, the law of lignin selective degradation on Phyllostachys pubescens substrate was studied. To obtain an appropriate white-rot fungus, the growth and lignocellulose degradation of 13 basidiomycetes on bamboo substrate were detected. The results indicated that Trametes sp.B1 had growth superiority and strong ability of selective delignification.The solid fermentation system of bamboo substrate was adopted and the relation between selectivity of lignin degradation and the law of lignocellulose degradation were further studied. The results showed that the selectivity of lignin degradation changed with culture time and had close relationship with lignin and cellulose degradation. High selectivity coefficient of lignin degradation was the result of strong lignin degradation and weak cellulose degradation. On the 20th day, B1 had the best selectivity of lignin degradation and the selectivity coefficient was 2.08, and the ratios of lignin and cellulose degradation were 26.4% and 12.7%, respectively.The influences of different factors on lignocellulose degradation and selectivity coefficient differed a lot. In the 18 factors, selectivity coefficients of lignin and hemicellulose degradation were promoted much by calcium chloride and xylan. Selectivity coefficient of lignin was improved from 4.38 to 66.57 by calcium chloride and from 12.91 to 41.45 by xylan.The mechanism of calcium chloride to enhance selectivity coefficient was studied, and the results showed that calcium chloride enhanced laccase activity as well as the ratio of lignin degradation. Although the activities of cellulase and xylanase were influenced little, the degradation of cellulose and hemicellulose altered a lot. The results implied that calcium chloride changed biological behaviours of strain B1 by some other approaches, besides changing enzyme activity. Cellulose degradation was very important to selectivity of lignin degradation.Considering the results of FTIR and the law of lignocellulose degradation, it can be presumed that strain B1 degraded lignocellulose by oxidative cracking. Firstly, soluble carbohydrates and hemicellulose in bamboo substrate were degraded and utilized as carbon resources and energy for strain B1 growth. Then, hemicellulose, lignin and cellulose were degraded.The study took Phyllostachys pubescens as material for the first time, and the basic research was carried out to enhance selectivity coefficient of lignin degradation. The law of lignocellulose degradation on bamboo substrate by strain B1 and the mechanism of calcium chloride enhancing selectivity coefficient was discussed. The pivotal factors influencing degradation selectivity were studied in this research as well. This paper provided important theoretic and practical significance for making full use of bamboo.