Study On Preservation And Activity Recovery Of Rumen Microorganisms

Straw is a kind of precious biomass resources. The yield of straw is about 840 million tons per year in China,690 million tons can be collected, while only 28.7%is utilized comprehensively. Most of straw are burned directly, resulting in serious air pollution, such as SO2, NO2 and particulate matter, etc. At present, there are a lot of technologies for straw utilization, including gasification, liquefaction, fermentation, and usage as industrial raw material. Among them, anaerobic fermentation of straw has been widely applied in rural areas, while existing some problems including low biodegradation rate, and low biogas yield by common microorganisms. Rumen microorganisms, the general term of the microorganisms taken from stomach of ruminants, have the ability to effectively biodegrade straws for biogas production. At present, there is no available method for rumen microorganisms preservation, which makes inoculums of straw anaerobic fermentation for biogas production become bottleneck in practical application.This work was divided into two parts for preservation and activity recovery of acclimated rumen microorganisms. In the first part, dried solid, undried solid and liquid rumen microorganisms were preserved at 4℃,-20℃ and room temperature, respectively. After ten days, the appropriate conditions for preserving rumen microorganisms were preliminarily selected based on the investigation on activity recovery of preserved rumen microorganisms in straw anaerobic fermentation. In the second part, on the basis of the above experimental results, Box-Behnken was used to design the experiment for investigating the impacts of three major factors (temperature, dosages of protective agent and inoculums) on activity recovery of preserved rumen microorganisms. Finally, response surface model (RSM) was used to analyze the experimental results for achieving the optimal preservation condition. The main results were as follows:(1) The activity recoveries of rumen microorganisms preserved at dried solid or liquid conditions were better. Moreover, due to environmental stimulation, the preserved rumen microorganisms produced more CMC enzyme during recovery process.(2) By using of RSM, the 3D surfaces and 2D contour maps were obtained to express the inter-relationships between two influence factors (among temperature, glycerin dosage and inoculums dosage) and four response values (CMC enzyme activity, reducing sugar concentration, TVFA concentration and CH4 percentage), respectively. Furthermore, the optimized preservation strategy was determined through solving the inverse matrixes of the four response values by using of Design-Expert software.