Construction And Effectiveness Of A High Efficient Complex Microbial System For Rice Straw Degradation

China which has a large population and a vast territory is in the fast lane of agricultural economic development. The total output of crop straw in China is amazing. The number is up to 800 million tons. Among them, the proportion of rice straw ranks first. With the method of constructing complex microbial system and biodegradation process to utilize rice straw, it can not only enhance the soil fertility and improve soil structure, but solve the problem of resource reuse and reduce production costs effectively. It has a guiding significance to recycle biomass resource conversion and reduce environmental pollution.The strain L4 with cellulose degradation ability was isolated from rice straw humus by sodium carboxymethyl cellulose medium. In this study, identification of strains includes three levels, morphology, culture characteristics observation and 16 S rDNA sequence analysis,respectively. Finally, the strain L4 was identified as Streptomyces griseorubens. In order to investigate the characteristics of the strain with rice straw degradation, we determined the activity of cellulase in rice straw fermentation system and the diameter of the transparent circle. Combined with cellulase composition characteristics, based on the characteristics of different strains of enzyme production, we selected the strain L4, Aspergillus niger and Trichoderma viride for constructing complex microbial system which has functional complementation and complete enzyme system. According to the results of complex microbial system antagonistic test, there is no inhibition ability among them. Complementary functional verification experiments showed that the degradation ability of chemical components of rice straw was significantly improved compared with the single strain.We analysis the activities of cellulase and ligninase of complex microbial system systemically in straw fermentation system. The results showed that the CMCase and β-1,4-glucanase were 83.89 U/mL and 66.56 U/mL, and the peak value of xylanase activity was 191.82 U/mL. The peak value of manganese peroxidase activity in ligninase was 8.21 U/m L. Compared with the strain L4, the four kinds of cellulase and xylanase activity were significantly improved. The peak value of manganese peroxidase activity was increased to 2.45-fold.We determined the dynamic change in the content of chemical components of rice straw. The results showed that the degradation rate of hemicellulose in rice straw was 56.87% after the end of the fermentation period, and the degradation rate of cellulose was 44.19%, which was slightly lower than that of the former. The degradation rate of lignin was only 18.46%. Compared with the strain L4, the degradation rate of cellulose was increased to 1.58-fold, the degradation rate of hemicellulose was increased to 1.14-fold. The research showed that the complex microbial system is more efficient in the ability of decomposition and utilization of rice straw. However, the utilization of lignin in the complex microbial system is far less than the carbohydrate in the chemical components of rice straw.We discussed the effects of pH and temperature on the degradation efficiency of complex microbial system. The experimental results showed that the optimum pH value was 7, the optimum temperature was 34℃. The whole structure changes of rice straw before and after degradation were observed by scanning electron microscope, which further validates the rice straw degradation efficiency of complex microbial system.