Study On The Lignocelluloses Characteristics Alteration Mechanism And Pyrolysis Characteristics Deconstructed By White-rot Fungi

As the exhaustion of fossil fuel and the increasing demand of energy, the low consuming and environmental bio-energy treated with white-rot fungi attracts more attention. However, few research is about the mechanism of lignin biodegradation and its influence on the biomass thermogravimetric characteristics biotreated by white-rot fungi. This thesis compared the lignocelluloses biodegradation mechanism by different white-rot fungi, investigated the relationship between the bio-modification and the thermogravimetric alteration of lignocelluloses, and obtained the most effective bio-modifying fungus Irpex lacteus CD2. By isolating the bio-modified lignin, the mechanism and relationship between the lignin bio-modification and thermogravemetric alteration have been clarified, as well as the enzymological mechanism of the extracellular lignin biodegradation system.By studying on the composition, element and structure change on FTIR, it's indicated that different white-rot fungi can greatly modify the structure of lignocelluloses. By disrupting the benzene structure of lignin unit, decreasing the crystallinity of cellulose and hemicelluloses, white-rot fungi can destruct biomass. Moreover, white-rot fungi can degrade the LCC linkages between lignin and hemicelluloses, releasing the cellulose and making the biomass more available to be treated for the production of bio-energy.By investigating the influence of bio-modification by white-rot fungi on the thermogravimetric characteristics of TG/DTG and the pyrolysis products of Py-GC/MS, it shows that the biodegradation and bio-modification can improve the lignocelluloses pyrolysis and increase the categories and content of the pyrolysis products. Biodegradation and Bio-modification can decrease 5.8%-9.5% of the activation energy, increase the efficiency and make the maximum acting rate of cellulose and lignin available to reach at the lower temperature which decreased 9-15℃and 20-36℃. By biodegrading with white-rot fungi, it can increase the fufural and phenol 6.0 fold and 2.1 fold respectively and decrease the release of carbon dioxide up to 39.6%. Demethoxy by white-rot fungi and the deconstruction of the side chain can decrease the content of dimethoxy phenol and the production of dipolymer.By isolating the deconstructed lignin by white-rot fungus Irepex lacteus CD2, the composition, element analysis and structure alteration have been studied. Results showed thatⅠ. lacteus CD2 can greatly deconstruct the structure of lignin. By oxidizing lignin, white-rot fungusⅠ. lacteus CD2 can degrade the benzene and conjugated ester linkages, produce huge number of conjugated and unconjugated carbonyl groups, decrease the methoxy groups and destroyed the linkages ofβ-5',5-5'andβ-Ο-4 ether bond, as well as the carbon linkages of coniferyl, guaiacyl and syringyl groups.By studying the alteration of thermogravimetric characteristics TG/DTG/DTA and the Py-GC/MS products of biodegraded lignin with white-rot fungusⅠ. lacteus CD2, it suggested that biodegradation byⅠ. lacteus CD2 can improve lignin pyrolysis, and influence the categories and content of the pyrolysis products. Biopretreatment can increase the activation rate up to 1.1-1.4 fold, and decrease the beginning and the end activation energy up to 45.9% and 40.6%. Biodegradation can increase the categories and the content of the lignin pyrolysis products, with phenols and benzenes increasing 2.92 and 1.27 fold, alcohols reaching as much as 3.73%. During the low-temperature pyrolysis, biodegraded lignin can produce 2-Methoxy-4-vinylphenol as much as 6.23%. By destroying the LCC linkages and demethoxy, biodegradation can decrease the content of fufural, benzofuran and dimethoxy phenol.By analyzing the SDS-PAGE, LC/MS and GC/MS of the extracellular enzyme system of white-rot fungusⅠ. lacteus CD2, it's indicated that the lignin degrading system ofⅠ. lacteus CD2 is none lignin degradation enzyme reliable biodegrading system which is unique and peculiar, and natural lignocelluloses can induce the secretion of some extracellular enzymes ofⅠ. lacteus CD2. Cultivated on the medium with natural lignocelluloses,Ⅰ. lacteus CD2 can produce cellulase, exo-beta-1,3-glucanase and peroxidase. The extracellular enzymes can greatly degrade lignin model compounds up to 60.8%, which might be carried out by adding hydroxylgroup and consuming low-molecular weight compounds.This thesis further explored the mechanism of natural lignocelluloses biodegradation by white-rot fungi, which can greatly improve the renewable energy production by using biomass biopretreated with white-rot fungi. This study first investigated the relationship between bio-modification and its effect on the lignocelluloses thermogravimetric characteristics, which can provide the theoretical evidence for the biomass pyrolysis improvement and products accumulation. By studying the unique extracellular lignin biodegrading system ofⅠ, lacteus CD2, we clarified the biochemical mechanism of lignin biodegradation by white-rot fungi.