Low-molecular-weight Compounds Involved In Lignin Biodegradation From Phanerochete Chrysosporium

Lignin is one of the most abundant renewable aromatic polymers but is known as the most recalcitrant biomaterial on earth. Thus, its biodegradation is a rate-determining step in the carbon cycle. White rot basidiomycete fungi are the only known microorganisms in nature that are capable of degrading lignin completely to CO₂ and H₂O, in which Phamrochaete chrysosporium has been well studied as a model strain. Both lignin peroxidases (LiP) and manganese peroxidases (MnP) were first purified from the culture fluid of this fungus. However previous studies indicated that lignin biodegradation cannot be accomplished efficiently only by the ligninolytic enzymes. And the electron microscopy studies have confirmed that the size of enzymes is too large to penetrate into the wood cell wall micropores at the early stages of decay to initiate the lignin degradation. These observations have led to the hypothesis that wood-rot-fungi might employ some small, diffusible active agents to initiate the breakdown of lignin. Many possible low-molecular-weight compounds and radicals have been suggested as likely mobile factors to permeate wood and initiate decay, such as hydroxyl radical HO", reactive oxygen species, veratryl alcohol, oxalate and Mn³⁺, and 3-hydroxyanthranilic acid, etc. But so far, all their functions in the progress of lignin biodegradation are only limited in hypotheses.The previous study in our laboratory firstly suggested that a low-molecular-weight peptide from celluloytic fungi can decompose cellulose into short fibers by oxidative mechamism in 1996, then the pure low-molecular-weight component named Gt factor from Gloeophyllum trabeum had similar function. The research in this dissertation was the further study based on the previous results. Character of low-molecular-weight system from P. chrysosprium was studied in detail and three novel low-molecular-weight compounds were purified, named Pc factor, Pc reducer, MnP promoter respectively based on their origin and characteristics. Pc factor had oxidative capacity for phenolic...