Effect Of Multi-strains Coupling Straw For Biogas Production In Anaerobic Fermentation

China is rich in cellulosic biomass resources, the total above 12 million tons. However, the use of a small amount of crop residues for feeding livestock, some for the compost heap, most efficiency is very low. With microorganisms to straw in anaerobic fermentation producing biogas, not only make the depth of the development of biomass resources and recycling, but also ease the energy crisis, environmental protection, improve the ecological. According to the composition characteristics of biogas, with straw as the raw materials in anaerobic fermentation, purified coupling agents bacteria as the inoculums, to study the key regulators of the content on the impact of biogas production in anaerobic fermentation. The results show that:1) With the Congo red plate method, 25 cellulose-degrading bacteria strains which can produce the hydrolysis are isolated from the loop rumen contents, and then screened a higher activity named ST16 among them with the Hungate anaerobic technology. According to the morphological characteristics, physiological and biochemical characteristics of the strain, found the ST16 are identified Enterobacter Hormaeche and Edwards. Through the single factor experiments of the best carbon and nitrogen sources, the results indicated that the CMC-Na as carbon source, NH₄NO₃ as nitrogen source produced the highest enzyme activity.2) Optimization of fermentation medium by orthogonal test showed that the best inoculation of carbon CMC-Na is 0.6%, nitrogen NH₄NO₃ is 0.20%, the concentration of Tw-80 is 0.025%, the concentration of ascorbic acid is 0.015%, which the enzyme activity can be achieved 3874.34μmol/(g·h). By optimizing the fermentation conditions for strain ST16 in aerobic and anaerobic, results show that: the optimal culture time of the strain is 96h (aerobic), 120h (anaerobic), the optimum temperature is 37℃, the optimum pH of the initial medium is 7, the optimum inoculation is 4% (aerobic), 8% (anaerobic); the final activity under aerobic conditions can be achieved 4210.32μmol/(g·h), anaerobic conditions 3415.76μmol/(g·h), and the highest activity of enzyme production time advanced. According to the preliminary enzymatic properties, the results indicate that: In the conditions of 50℃and pH 7.0, the activity of crude enzyme was maximum, and the stability is discrepancy if the temperature more than 70℃, also can be seen the Mn²⁺, Fe²⁺ can be significantly enhanced the enzyme activity.3) With the Hungate anaerobic technology, a methanogen strain named FC1 was isolated from sludge in experimental field in Hubei Academy of Agricultural Sciences, the colony of FC1 was straight or slightly short rod in the rolling tube, single or in chains, Gram-negative, with sports, do not form spores, the colonies round, white, smooth surface, transparent, can grow with formate, observed in fluorescence microscope can find the colonies with green fluorescence. The optimum growth temperature was 37℃, pH was 7.0, according to the morphological, physical and chemical characteristics and 16S rDNA sequence analysis showed that the strain is small methane particles Methanocorpusculum parvum, and a mesophilic bacteria.4) Through the acid bacteria, methane and cellulose mixed to compound a group of highly efficient strains, make the composite agent strains into straw by anaerobic fermentation, and found that the most appropriate inoculation of complex strains access to 10%. Analysis the fermented liquid composition of the best experimental group and control group showed that, with the straw by coupling microflora fermentation, the pH, TS and VS are small compared to the control group, and the content of organic acids acetic, propionic and butyric acid are also less than the control group, the content is 20.24%～24.53%, 44.08%～45.37% and 35.47%～51.20%,respectively, which indicating that high gas efficiency was made by increasing the capacity of methane synthesis by coupling bacteria, rather than by promoting the growth and advantages of the single bacteria, while composite microbial system is also an effective way to improve the biogas yield and quality.