Screening Of Strains For Strengthen The Methane Fermentation Of Straw And Study On Fermentation Conditions

Straw resources is rich in China, various types of straw were produced about 7 million tons every year, but the utilization of straw is still relatively low, in addition to a small amount of compost used as feed materials and also fields, most of them local accumulation or direct burning, not only a waste of resources, but also caused serious environmental pollution. Use Combined biological agents on the straw for processing, transform straws by the anaerobic fermentation into biogas, not only can addresses the the shortage of raw materials in promotion of biogas building in rural areas but also solve the rural prevalence problem of "straw stacked" and "straw burning". Thus, made a Straw DVS ferment mixing by high cellulase activity microbe and methanogen, can accelerate the decomposition of straw and improve the production of biogas, is an effective way for straw to biogas production.In this paper, the cellulose decomposing bacteria preserved in laboratory were rejuvenated and screening, after preliminary screening by Congo red plates, rescreening by wheat bran solid state fermentation, a high yield cellulase strain of Aspergillus niger X-2 and Trichoderma koningii H-5 were separated. Aspergillus niger X-2’s cellulase activity was 2087U/g, higher 52.35% than the original strain; koningii H-5 of the activity was 1649 U/g, higher 45.54% than the original strain. After consecutive transfer of culture for 6 generations, the strain X-2 and H-5 also have a stable cellulase enzyme output.The culture conditions of Aspergillus niger X-2 and Trichoderma koningii H-5 were optimized by Single factor tests, obtained the best culture conditions of Aspergillus niger X-2 as fellows:culture temperature was 30℃, the culture time was 72h, compound carbon ratio of straw/wheat bran the mass ratio of 0:10, the best nitrogen source was yeast extract, the addition of nitrogen source was 1%, the Solid-Liquid Ratio was 1:1, inoculum size was1%, bottling capacity was 30g/250ml. of the best culture conditions of Trichoderma koningii H-5 as fellows:culture temperature was 30℃, cultured for 5 days, the ratio of straw composite carbon/mass ratio of 2:8 wheat bran, the best nitrogen source was yeast extract, the addition of nitrogen source was 2%, the Solid-Liquid Ratio was 1:1.5, inoculum size was 1%, bottling capacity was 30g/250ml.Under the optimum culture conditions, Aspergillus niger X-2 and Trichoderma koningii H-5, respectively spore production of up to 33 billion/g and 46 billion/g.Two strains Z-1, Z-2 were isolated from the biogas slurry sample by the Hungate anaerobic technology. Strain Z-1 was spherical, generally irregular spherical aggregates, G-, non-motile; colonies which in the rolling tube were round, white, opaque; The strain can use H2/CO2 and methanol as a substrate, the optimum temperature was 35℃, the optimum pH was 7.0 and the optimum NaCl concentration was 0.2mol/L. Strain Z-2 was oval-shaped, single or in small clusters of growth, G-, does not produce spores, non-motile; colonies in the roll tube were round, light-yellow, opaque; The strain can use H2/CO2, sodium formate and acetate as a substrate, the optimum temperature was 35℃, the optimum pH was 6.5, the optimal NaCl concentration was 0.1mol/L.