Screening And Degradation Characteristics Of Rice Straw Cellulose Degradating Composite Microbial System I-D

[Background] Energy is the foundation resources of social and economic sustainable development, in order to guarantee the economic development, developing new energies has become the imperative strategy. Rice straw cellulose content is high, planting area in China is wide, it is an important material of biomass energy development and utilization. So screening of rice straw cellulose degradating composite microbial system and studying its degradation characteristics become the important direction of majority researchers to explore the effective utilization method of straw.[Objectives] Screening of efficient rice straw cellulose degradating composite microbial system and studying its degradation characteristics,in orde to provide reference for its application.[Methods] Using long-term cultivation of paddy soil and piled up in a month of rice straw heap corruption as bacterial, adopting the method of restrictive screening.Using rice straw powder as the sole carbon source for the PCS medium to screen and domesticate the straw cellulose degrading composite microbial system;The gradient experiment and the response surface method are adopted to find the composite microbial system’s optimal fermentation parameter. Using DNS method and anthrone method to determine the CMCase and contents of total sugar.Using single colony separation method,aesculin and Congo red method, gene sequence identification and so on method study of single colony in the composite system.[Results](1) Composite microbial system I-D acclimatization to the fourth generation will completely collapse the filter paper which as a symbol indicating within7days and the pH value of the fermented liquid stabilize between eight and nine, extend to the tenth generation after degradation it’s efficiency has not degraded, pH value is stable at about9. Using I-D fermentation7days, the filter’s disintegration rate is100%, the pH value of fermentation liquor is9.(2) The single factor’s optimal value range which affecte composite microbial system’s degradation efficiency is that temperature is30℃-40℃, time is7-9days, pH value is8-10. After response surface method optimized, showed that optimal cellulose degradation parameters of composite microbial system I-D is that time is7.7days, fermentation temperature is37℃, initial fermentation pH value is10, daily average degradation rate of rice straw powder under optimal fermentation parameters was7.87%.(3) The CMCase activity of composite microbial system found that CMCase activity in the fermentation process is around20U/mL and the highest is24.2U/mL, it is double than single bacteria; The soluble total sugar content in the fermentation process is about110-150μg/mL, and it’s changes consistent with the bacteria growth rule.(4) Screened179strains bacteria, did not screen fungi, there are6strains have CMCase activity,7strains have beta-glycosidase activity. Gram staining the CMCase activity strains D6showed that it’s gram-negative bacterium,16S rDNA sequence identification initially determined it’s Bacillus sp..[Conclusions] Successful screening efficient rice straw cellulose degrading bacteria compound I-D, provided an important basis for efficient using of rice straw; Studying the degradation characteristics of composite microbial system, obtained the optimal fermentation conditions lay the foundation for it’s industrial application.