Research Of Lignocelluses Biodegradation By Different Microorganisms In Agriculture And Forestry Waste Composting

Now, composting has become a technology of agricultural and forestry waste utilization. Composting can recycle the agricultural and forestry waste. We can get a good ecomonic benefit, realize the clean production, and protect the environment from pollution. The waste treatment technology of composting entered a new stage of science development. In order to improve the disadvantage of composting, increase the compost efficiency, and make it can be used in large scale, many researchers at home and abroad carried out a lot of research on the field of composting equipment, composting technology, and microbiology of composting, et al. The biodegradation of limits speed organic compound is considered as the key of composting. In agricultural and forestry composting, the lignocellulose is the major organic compound that limiting composting speed. This organic compound has hard structure, and is separated difficultly. Especially the lignin, it is considered the key of fast compost, its degradation is essential for the operation of compostingIn the paper, lignocelluloses biodegradation and its microbial characteristics during composting of agricultural wastes were studied. Through the traditional method, we get the rule of microorganism in lignocelluloses degradation, and sieve the microorganisms that have good ability of lignocelluloses degradation. We studied the characteristic and the mechanism of lignocelluloses degradation by different organisms in solid fermentation, and applied the ergosterol as the indicator of fungal biomass in composting.The results obtained through the traditional method indicated that lignocelluloses were mainly degraded during the thermophilic phase and maturation phase of composting. In the process of composting, it is not only one kind of organisms act in the lignocelluloses degradation, futhermore the ability of lignocelluloses degradation by the microorganisms is different. In the initial stage of composting, the degradation of lignocelluloses by different bacteria is not in evidence. The degradation effects of all sorts of microorganisms are important to the composting. During the thermophilic phase, the fungi and actinomycetes are major microorganisms in the degradation of lignocelluloses. The amount of lignocelluloses degradation microorganisms is high, but their ability of lignocelluloses degradation is weak. This stage is not the suitable period for sieving organisms. In the period of first fermentation turning into the second fermentation and in the initial stage of second fermentation, the bacteria and fungi are the major microorganisms of lignocelluloses degradation. The lignocelluloses degradation ability of fungi is very strong. It is the best stage for sieving lignocelluloses degradation microorganisms. During the later period of composting, the fungi and actinomycetes are the major microorganisms in the degradation of lignocelluloses. The degradation of lignocelluloses occurred in the maturation phase and the second fermentation of composting. Polyphenol oxidase (PPO) and peroxidase (POD), especially PPO was found to be the most important catalyzer in lignin degradation. Bacteria, fungi and actinomycetes with lignin degrading ability changed greatly during every compost phase. Actinomycetes were found to be the most effective microorganism to degrade lignin followed by fungi and bacteria.Compared with the lignin degrading ability and their enzyme production of three strains of bacterium, actinomycetes and fungi, which isolated from the agricultural waste composting, we can get the conclusion that the bacterium X6, the actinomycetes F2 and the Aspergillus niger have the ligninolytic ability. They were capable of utilizing several lignin model compounds, and degrading natural lignin. Especially they were capable of utilizing phenolic and nonphenolic lignin model compounds. Five kinds of enzymes were believed to be the most important catalyzes in biodegrading process. They are lignin peroxidase, Manganses peroxidase, Laccase, Cellulase and Hemicellulase. And they always work synergistically. But the amount of their enzyme production is different by bacterium, actinomycetes and fungus. The peak value of the three microorganisms'enzyme production appeared in the period of its stable growth. After 30 days'incubation, the degrade rate of lignin by the bacterium X6 was 9.43%, however the degrade rate of lignin by the actinomycetes F2 was 11.5%. At the same time, the cellulose and hemicelluloses were degraded greatly. The mechanism of their for lignocelluloses degradation is different to fungus, the lignocelluloses degradation by them occurred in the primary stage of solid fermentation. However, The peak value of A. niger enzyme production appeared in the period of its stable growth. After 30 days'incubation, the degrade rate of lignin by A. niger was 16.87%. At the same time, the cellulose and hemicelluloses were degraded greatly. The mechanism of A. niger is analogy to white rot fungi, the lignocelluloses degradation by fungi occurred in the subsequent stage of solid fermentation.In addition, the structure of the untreated straw and treated straw were analyzed by infrared spectroscopy. It was observed that the structure of treated straw was greatly altered, and the effect of three microorganisms to lignocelluloses is different.Ergosterol is the important component of the fungal membrane, and having stable structure. This makes it a suitable indicator for growth of fungi. In the paper, isolation and determination techniques of ergosterol as the indicator of the fungal biomass were reviewed. We compare the methods of traditional cultivation and the applying the ergosterol as the indicator of fungal biomass in composting. We can draw a conclusion that the data that get through the method of traditional cultivation is inexact. The method of applying the ergosterol as the indicator of fungal biomass in composting is exact, simple and convenient. It is very important to research the fungi of composting.