Study On Law Of Degradation Sequence In Lignocelluose By White-rot Fungi

In nature, lignocellulose is a kind of important regeneration resource, but it can't be fully utilized at present because of the difficulty in degradating and transforming lignin. White-rot fungi are a kind of the effective microbes that have strong potential to degradate lignin now.By detecting 6 strains' Pleurotus growth status and laccase activity on different substrates, strain BP2 is screened from the six strains, because it has the highest speed in growth and the best ability to secrete laccase. Comparing to Phanerochaete chrysosporium(CD0) and coriolus versicolor(CD1), it has not only growth superiority but also strong ability in laccase secreting and lignocellulose degradation.It was showed in the study of determining the content of cellulose,hemicellulose and lignin in lignocellulose substrates accurately that the quantitative assay through dispersion method or Van Soest, which evaluate degradative status of lignocellulose by white-rot fungi, is feasible. Detecting the ratio of degradating hemicellulose, cellulose and ligin by dispersion method, the results indicate that strain BP2 has superiority and selectivity of degradating hemicellulose and lignin in maize stalk, straw stalk and spill substrates. In 50 days, lignin is degradated 33.9%,53.2% and 43.5% respectively, and selectivity coefficient is 0.20,0.26 and 0.49; and hemicellulose is degradated 32.1%,57.1% and 35.9% respectively, and selectivity coefficient is 0.44,0.45 and 0.19 in maize stalk, straw stalk and spill substrates. Cellulose is always degradated a little, regardless of the degree of lignification. Strain CD1 has similar superiority and selectivity to strain BP2 in degradation. So does strain CD0 in maize stalk and straw stalk.On the other hand, by studying the changes in chemistry and surface of specimen by a fourier transform infrared (FTIR) spectroscopic and Scanning electron microscope (SEM) image respectively, the results show that strain BP2 degradate lignocellulose by oxidative cracking.The researches of relative changes in the intensity of lignin associated bands (at1630,1510,1325and 1265cm-1) ,hemicellulose and cellulose associated bands (at 1738,1375, 1158 and 898 cm-1),and the relative intensity of C=O,OH and COOH characteristic bands, approve that lignin is degradated obviously by strain BP2 , while cellulose and hemicellulose are degradated a little. When the degree of lignification strengthens, the relative intensity of associated bands is magnified, the superiority of hemicellullosedegradation is more obvious, and the degree of lignin degradation becomes better. Hemicellulose, lignin and cellulose are oxidative degradated by strain BP2. This biotreatment breaks the ring of their structure and firstly produces small molecule segment (such as lignin monomer), small acid substance (such as lactic acid and glucose acid), small ester substance(such as glucose ester), and so on. All these substances are utilized by strain BP2.The changes on spectrum of fermentation specimen by strain CD1 and strain CD0 are similar to the law of strain BP2.The hemicellulose and lignin that packed by cellouse are degradated by strain BP2, and the strain also can make the lignocellulose substrate fibrosis. These conclusions are obtained by analyzing SEM image. Besides, the study of law on laccase secretion shows that the degradation of lignin is not positive relative to laccase.The processing of degradating lignocellouse substrate by Strain BP2 follow the law: firstly, small carbohydrates (soluble sugar) are utilized and hemicellulose is degradated; then hemicellulose and lignin are degradated; cellulose, hemicellulose and lignin are degradated at last. Strain BP2 has superiority and selectivity to degradate lignin and hemicellulose. Strain CD0 and strain CD1 have similar degradation laws to strain BP2.The strain BP2 is cultured in lignin, hemicellulose, cellulose and mixed substrate respectively, the results show that strain BP2 grows poorly on pure substrate and lignocelulose are degradated little. Small carbohydrates influe...