The Primary Research On Complex Microbial Community In Municipal Solid Waste Composting

In recent years, developing new technology, increasing efficiency and improving the quality of product were the key points of the research on municipal solid waste composting. Developing the high efficient complex microbial community was the hot point in this area especially. In the recent reports about efficient complex microbial community, the cellulose decomposing microbe and lignin decomposing microbe were used widely. It was often objective that selecting the cellulose and lignin decomposing microbe was, being lack of studying on the relationship between these microbes. So it was often accidentally to get proper results, and the applicability of there results were limited. In this paper, the propose was to separate and screen cellulose decomposing microbe from the composting process, study the process of cellulase production in solid state fermentation, carry out the primary study on mixed culture in order to find proper combination of these special microbes to decompose the cellulose or lignin.First, four high efficient cellulose decomposing microbes were screened from the composting process by the separating by cellulose agar and the screening by cellulose-congo red agar and solid state fermentation. The microbe named X was the best one in cellulase production and cellulose decomposing.Then, in order to see the process of cellulase production and the culture conditions, the effects of different conditions on cellulase activity in cellulase production by the microbe named X were studied by solid state fermentation. The liquid-solid ratio is the most greatly influencing factor during the whole process of the solid state fermentation. In the initial stage of the fermentation, the temperature can affect the cellulase production relatively greatly because it can affect the growth of the microorganisms. The effects of initial pH and the number of inoculum were not significant. Considering the whole process of the fermentation, the temperature, initial pH, liquid-solid ratio and the number of inoculumwere suggested to be 30C, 4, 7 and 5%, respectively. By investigation on the effects of different carbon sources on the cellulase production, adding the proper amount of maltose and cellobiose was proved to be useful for cellulase production. The primary function of cellobiose is stimulating the endoglucanase production. The differences of effects of defferent nitrogen sources are great. Some nitrogen sources are hard to be utilized by the microorganism. The yeast extract and (NH4)2SO4 are proper nitrogen sources for this microorganism. Adding the 0.1% of surfactant of Tween 80 was proved to be be useful for cellulase production.At last, basing above results, the mixed culture of six cellulose decomposing microbes and eight lignin decomposing microbes were studied. Nine couples of microbes were selected by their modalities on the basic agar, named S + 10, AF93251+2, AF 93251 + 10 , X+3 , X+10, AF93252+2, AF93252+5, P+5, P+10.The cellulase, xylanase, laccase and lignin peroxidase activities of three couples named AF93251+2, AF93252+5, X+10 were studied by mixed culture in solid state fermentation. The results, indicated that the couple named AF93252 + 5 was the best one in cellulase and xylanase production by mixed culture. This couple could be taken further study although it wasn't the best in laccase and lignin peroxidase production.From above results, it was obvious that the better effects on decomposing and enzyme production could not be acquired by mixing cellulose and lignin decomposing microbes randomly, although these microbes were all fungi. Many interactions such as competition and symbiosis between these microbes were unknown to us. So, it was necessary to study these interactions to make high efficient complex microbial community for municipal solid waste composting.