Research On Characteristics Of Degradation And Transformation Of Lignocellulose By Phanerochaete Chrysosporium And Its Key Functional Enzymes

Lignocellulose is a macromolecular complex consisted of lignin, cellulose and hemicellulose. Lignin is a highly irregular and insoluble polymer, chemically bonded by covalent linkages of hemicellulose. Therefore, the lignin-carbohydrate complexes enwrap cellulose in plant cell wall. This complex structure inhibits lignocellulose transformation, and consequently slows down the lignocellulosic waste degradation process in nature. Therefore, it is generally accepted that lignin decomposition is the rate-limiting step during composting. White-rot fungi are currently being used not only in the biodegradation of lignin, as they secrete the low specificity and strong oxidative ligninolytic enzymes (such as Lignin Peroxidase, Mn-dependent Peroxidase, lacases et al) which could oxidatively degrade lignin and mineralize them into CO2and water. Phanerochaete chrysosporium (P. chrysosporium) is a typical representative of the white rot fungus; therefore, this study selected P. chrysosporium as research subjects to study the lignin degradation characteristic and mechanism of P. chrysosporium and its key functional enzymes in solid-state fermentationand and composting system.In solid state fermentation conditions, the high inoculum concentration of P. chrysosporium would affect the degradation of lignocellulose degradation efficiency. However, the low concentration of it would lead to less degradation. In the experimental range, the best inoculum concentration was4mL/35g dry sample. In this inoculums concentration, the lignin degradation rates of up to39.1%. Furthermore, since the lignin barrier is broken, the degradation of hemicellulose has also been significantly improved by inoculum of P. chrysosporium. Scanning electron microscope and UV spectrum analysis results also show that, in this concentration, the damage of lignocellulose is most severe.The results show that P. chrysosporium can significantly improve the degradation of lignin and hemicellulose rate, but the degradation of cellulose is not very obvious. In addition, the effect of P. chrysosporium on lignocellulose transformation was also investigated in this experiment. Therefore, in the composting process, the humus, humic acid, fulvic acid and the humification index of dynamic changes were monitored. The results show that the formation of FA was not obviously influenced by the inoculum of P. chrysosporium, while the HA was significantly enhanced by the inoculum. Humification index also revealed that the composting became mature and steady earlier with P. chrysosporium. And the humification degree of compost was also enhanced. UV and FTIR analysis of humic substances indicated that P. chrysosporium could increase the aromatic content and decrease the polysaccharide and aliphatic contents of composting. With the composting progresses, the compost with P. chrysosporium of humic acid aromatization process was accelerated. This means that P. chrysosporium would improve the degree humification and stable the composting process. Finally, the clustering results indicated that inoculation of P. chrysosporium can effectively shorten the composting time, and promote the early maturity and stability of the composting.The influence of guaiacol and compounded carbons sources co-degradation on enzymes of white-rot fungi was studied through the orthogonal experiment. The results show that carbons with different structures and guaiacol have remarkable effect on enzymes secreting by P. chrysosporium. High concentration of guaiacol can enhance enzymes production. After optimumization of various factors, addition of guaiacol2mmol/L, glucose2.5g/L, dextrine5g/L in culture medium can significantly promote enzymes production. CMCase and xylanase produced by P. chrysosporium are little affected by exterior environment. According to the correlativity between the CMCase and the xylanase analyzed using linear regression, a postive correlation the CMCase and the xylanas is found.The above high activity of crude enzyme solution added to the lignocellulose-rich compost system. And the effects of the enzymes on lignocellulose degradation and transformation were studied. The results show that adding enzyme is mainly beneficial to break the barrier formed by the lignin, which resulted in the hemicellulose can be exposed. Therefore, the degradation of hemicellulose was also enhanced. These results were samiler to the inoculation of P. chrysosporium. Humuic results indicate that the effect of enzymes in the formation of humic acid was mainly observed after30day. And at this stage the enzymes resulted in the chang of humic molecular structure, however, the significant effect on organic matter degradation was not obvious. During composting, the peak activity of LiP and MnP are alternating, and the effect of enzymes on LiP is mainly after30day. FTIR spectroscopy results indicat that the addition of enzyme was beneficial to the demethylation and then promoted side chain oxidation of lignin. The degradation of aliphatic compounds was accelerated and aromatization was enhanced simultaneously. While GC/MS results showed that addition of enzymes could promote depolymerization of dipolymer and double bond oxidation to accelerate the subsequent lignin degradation. These effects were beneficial to material supply of nutrients for microbial community and further degradation and transformation of lignocellulose during composting.The objective of this study was to assess the response of carbon utilization profiles to addition of ligninolytic enzymes during composting. Carbon utilization (measured by Biolog EocPlateTM) revealed that, in the treatment, average well-color development (AWCD) of amino acids was significantly enhanced after day6(P<0.05), while AWCD of carboxylic acids and polymers were increased after day15. The microbial community metabolic of cluster analysis showed that when the enzymes were added into the compost, the carbon metablic capability of intermediate metabolite was improved. Principal component analysis (PCA) confirmed the differentiation of the treatment and the control. The results indicated that, when the enzymes were added, microbial communities enhanced the metabolic capability of miscellaneous, polymers, amino acids and amides carbon substrates, which results in the efficient degradation of organic carbon. In addition, cluster analysis of each composting phase showed that the effects of the enzymes on microbial community metabolism were mainly observed on6d and30d, which promoted the composting process.