Study On Technological Condition Bamboo Lignin Degradation By White-rot Fungi

Lignin is one of the largest number of natural macromolecular compound, the study on lignin biodegradation showed that white-rot fungi was a unique kind of microorganism which could degraded lignin to CO2 and H2O in pure culture, so lignin selective degradation by white-rot fungi was hot spot in biotechnology research.In this paper, the combination of Phanerochaete chrysosporium, Trametes cinnabarina and Pleurotus ostreatus were selected as experimental materials, The solid fermentation system of bamboo substrate was adopted. To obtain appropriate white-rot fungi, the growth and lignocellulose degradation of 3 basidiomycetes on bamboo substrate were detected. The results indicated that the combination of the three species of white-rot fungi had strong ability of selective delignification.The effect of different culture conditions(temperature, pH value, percentages of quality of culture medium and bamboo) and various additives(hydrogen peroxide, benzyl alcohol) on lignin degradation was studied, The optimal technological conditions of bamboo lignin degradation by white-rot fungi efficiently were discussed.The influences of different culture conditions on lignin degradation and selectivity coefficient differed a lot.White-rot fungi were fermented in bamboo medium for 30 days under different culture temperatures(24℃, 27℃, 30℃, 33℃), the results showed that at a culture temperature of 30℃, MnP and LiP enzyme activities were the highest, reached 225 U/L and 810 U/L respectively; at a culture temperature of 33℃, Lac enzyme activity was the highest, reached 139 U/L; at a culture temperature of 30℃, lignin degradation rate was the highest, reached 46.6%, selectivity coefficient was 4.28.The effect of four different pH(pH value of 2.5, pH value of 3.5, pH value of 4.5, pH value of 5.5)on lignin degradatio was studied, the results showed that when the value of pH value was 3.5, Lac and LiP enzyme activities were the highest, reached 150 U/L and 1180 U/L respectively; when the value of pH value was 4.5, MnP enzyme activity was the highest, reached 350 U/L; when the value of pH value was 3.5, lignin degradation rate was the highest, reached 48.6%, lignin selectivity coefficient was 5.46.The effect of four different percentages of quality of culture medium and bamboo on lignin degradation was studied, the results showed that when the percentage of quality 110%, Lac, MnP and LiP enzyme activities were the highest, reached 160 U/L, 360 U/L and 1100 U/L respectively, lignin degradation rate was also the highest, reached 50.2%, lignin selectivity coefficient was 4.67.After adding hydrogen peroxide with different concentrations(0.001%, 0.01%, 0.1%, 1%), the hydrogen peroxide enhanced lignin-degrading enzymes activity as well as the lignin degradation rate. when the concentration was 0.1%, Lac enzyme activity was highest, which was improved from 160 U/L to 210 U/L, when the concentration was 1%, MnP and LiP enzyme activities were the highest, which were improved from 320 U/L to 550 U/L and from 1000 U/L to 1450 U/L respectively, when the concentration was 1%, lignin degradation rate was improved from 44.2% to 58.6%, lignin selectivity coefficient was improved from 3.95 to 5.14.After adding benzyl alcohol with different concentrations(0.001%, 0.01%, 0.1%, 1%), when the concentration was 0.1%, Lac and LiP enzyme activities were the highest, which were improved from 160 U/L to 260 U/L and 1000 U/L to 1500 U/L respectively, when the concentration was 1%, MnP enzyme activity was the highest, which was improved from 320 U/L to 430 U/L, lignin degradation rate was improved from 47.23% to 59.5%, lignin selectivity coefficient was improved from 4.1 to 4.84.The above results showed that when culture temperature was 30℃, pH value was 4.5, percentages of quality of culture medium and bamboo was 110%, the concentration of hydrogen peroxide was 1%, the concentration of benzyl alcohol was 0.1%, the combination of three species of white-rot fungi as experimental strains, the enzyme activity was the highest, the effect of lignin degradation was the best as well,which was the optimum technological conditions.