| China is a agricultural country with a long history, large farming area, high output of agricultural products.Because of this, China can provide plenty of food for the people of the whole society, and leaving a lot of agricultural wastes at the same time, it will cause some economic and enviro nmental problems. In order to solve this problem, the utilization of agricultural wastes for biogas, which can not only produce renewable energy for the social, providing some economic benefit, and making agricultural wastes to be appropriate and proper treatment, to solve the environmental problems caused by improper treatment of agricultural waste. Making use of agricultural wastes to conduct the development and application of renewable energy is very necessary.This experiment used agricultural wastes(cow dung and straw) as the research object, proceeded anaerobic fermentation to produce methane,and isolated methanogens from the biogas slurry. Taken biogas slurry as sample source of methanogens, according to the methanogen specific coenzyme FM420, at a wavelength of 420 nm, blue-green fluorescence can be observed. As the separation of methanogens, taken advantage of the Hungate anaerobic culture method, completed the separation of the methanogens from the biogas slurry,and eventually obtained two methanogens strains Lin1 and Lin3. The physiological and biochemical characteristics of the isolated Lin1 and Lin3 were determined by morphological characteristics, physiological and biochemical characteristics, and the classification status of methanogens Lin1 and Lin3 were determined.The results of this experiment were that the of the strains Lin1 was spherical, cultivation of 12~15 d,the transparent and single colony was visible. Growth salinity range 0~5% Na Cl(w/v)(the optimum Na Cl concentration was 0%), growth temperature range 20~40°C(the optimum was 35°C), growth p H range 6.0~9.0(the optimum was p H 7.0), phylogenetic analysis showed that strain Lin1 and Methanomassiliicoccus luminyensis belong to the same branch in the evolutionary relationships. The strains Lin3 was rhabditiform, and the neat and transparent single colony was detectable in the solid culture after 12~15 d for incubation time, growing salinity range from 0%~5%Na Cl(w/v)(the optimal Na Cl concentration was 0%);the appropriate growth temperature was at the range of 20~40°C(the optimum was 35°C);the appropriate growth p H was at the range of 6.0~9.0(the optimum was p H 7.0). Based on 16 S r RNA gene sequences. Phylogenetic analysis showed that Lin3 and Methanobacterium curvum belong to the same branch in the evolutionary relationships.Made use of the two-phase anaerobic reactor as fermentation device for the test, mixed cow dung and straw as a fermentation substrate, in the temperature of 37°C, proceeded methanogenic fermentation. In the process of fermentation, a series of physical and chemical conditions were optimized,including raw material pretreatment, the initial p H value, substrate concentration, substrate material mixing proportion, adding methanogens. Through compared methane yield of anaerobic fermentation system, determined the optimal fermentation conditions. Drawn from experimental result, came to the conclusion that the appropriate fermentation temperature of 37°C, the starting p H value of the fermentation was set to 7.0, the pretreatment of the raw material for microbial degradation, set substrate concentration to 15%, the mixing ratio of cow dung and straw was 1.5:1. Chosen above-mentioned fermentation conditions as the optimal fermentation conditions for the test. Respectively, added the methanogens M. luminyensis and M. curvum as inoculum to the fermentation system(Tap water, cattle manure and straw).The experiment results shown that the methane yield of the fermentation system, which added methanogens was significantly higher than the fermentation system did not add any inoculum. |
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