Screening Of Lignin-degrading Composite Microorganism From Composting And Its Physiological Characteristics

The lignin of agricultural wastes is difficult to be effectively degraded and reduced, and also conserved as resources, for the structure of lignin is extremely complex. In nature, the complete degradation of lignin is the results of fungal, bacterial and microbial community working together. Therefore, the development of the composite microbial of lignin degrading has significant meaning.This experiment was done aiming to improve effective degradation of lignin. Three composite microorganisms (MC1, MC2 and MC3) able to degrade lignin were screened from three stages of agricultural waste composting by a series of domesticated cultivation, and the three stages were warming stage, cooling stage and falling stage, respectively. The composite microorganisms with the most efficient lignin-degrading ability was selected through initial and further screenings, and their stability was studied then, its optimum integrative culture conditions are as follows to improve the lignin-degradating ability of MC1, MC1 degradating the natural lignin was reserached at the last.The results of initial and further screenings showed that composite microorganism MC1 screened from the warming stage had the strongest ability to degrade lignin. All the values of the activities of lignin peroxidase, manganese peroxidase and laccase reached the maximum values after 6 days at 37℃under the static culture of submerged fermentation, which were 258.37 U L-1,486.39 U L-1 and 49.25 U L-1,respectively, and the lignin degradation rate was 36.25% after 14 days. The subculture of composite microorganism MC1 showed that it was very stable.Orthogonal experiment is adopted to study MC1's nutritional regulation. The results showed that the composite microorganism MC1 screened from the warming stage has the best ability to degrade lignin; rotate speed is 120 rpm; the first carbon source is sucrose, nitrogen source is peptone; ATBS, Veratryl alcohol, Tween-80, Cu2+and Mn2+should be added, the second carbon source is added after 2 days. Undering the optimum integrative culture conditions, the enzyme activity of LiP, MnP and Lac after 6 days are 579.91 U L-1, 882.49 U L-1 and 80.94 U L-1, respectively. The lignin degradation rate is 46.75% after 10 days.MC1's degradation of natural lignin experimental result showed that the composite microorganisms on the natural degradation of lignin has a strong, solid-state fermentation at 30 d, the lignin degradation rate was 48.75%, lignin degradation of rice straw in the structure was seriously destruction of refractory macromolecules long bond was cut into easily degradable hydrocarbons of small hydrocarbon molecules with short keys.