The Study Of Influence Of Extracellular Enzymes On Lignin Degradation And Microbial Community's Succession

Organic solid waste, especially agriculture waste, contains a lot of lignocellulose, which is the ratelimiting factor of composting, so the degradation of lignin is essential for the operation of composting. All of the biochemistry changes in the composting due to the enzymes, so the main objective of this study was to obtain more useful information about lignin-degrading extracellular enzymes of Phanerochaete Chrysosporium.The effects of extracellular enzymes on the change characteristics of molecular structure of milled wood lignin (MWL) in solid state fermentation were studied. The results showed that surface of MWL was dispersed from the whole to the small granular. The spectroscopy analysis indicated that structure of rice straw MWL was consisted chiefly of guaiacyl, extracellular enzymes had higher biodegradability on guaiacyl, and promoted aliphatic compounds to decompose, and promoted reactions of aromatic ring cleavage and demethylation.The influences of extracellular enzymes on the composting process in agricultural waste composts were investigated. Extracellular enzymes made the pH tended to be stable and improved consumption of organic matter. Fourier transform infrared spectroscopy showed that extracellular enzymes had great positive effects on the ether bond of syringyl, guaiacyl and cellulose framework structure. The humus datas showed that extracellular enzymes promoted to form the humus, especially to form humic acid.The effects of extracellular enzymes on the lignocellulose degradation and the succession of microbial community in agricultural waste composts were studied. Extracellular enzymes had negative effect on total quinone content in the initial stage of composting, but this inhibitory effect decreased gradually along with the composting process. At the end of composting, the extracellular enzymes improved the diversity and evenness of the microbial community, and significantly increased the degradation amount of lignin and hemicellulose. The quinone profile showed that the bacteria indicated by MK-7 as major quinone were predominant after the mesophilic phase, and there was no new dominant microbe found in the composting with the enzyme additive. But extracellular enzymes had great positive effects on menaquinones and promoted the amount of long-chain menaquinones during the final phase of composting. The principal component analysis indicated that the greater effects of extracellular enzymes on the microbial community were observed on 3 d and 40 d than other days, which was consistented with the dissimilarities analysis result. In addition, the extracellular enzymes enhanced the effect of fungi in the whole system.