Screening And Optimization Of Cultivation Of Compound Bacteria For Fermentation Acid With Rice Straw

Short-chain fatty acids play an important role in chemical, food, medicaland livestock industries, but the most of the raw materials for industrialproductiom of the short-chain fatty acids come from non-renewable sources suchas oil, natural gas and coal and so on. As fossil fuels are not sustainable resources,using anaerobic fermentation of straw technology could not only get highvalue-added products （short chain fatty acids）, but also solve straw wasteproblem. But due to the complex structure of the straw, pure bacteria’sdegradation ability is poor. The composite of a variety of bacteria flora canweaken the inhibitory effect of the intermediate product. Moreover, thecooperative metabolism among species during the fermentation process caneffectively improve straw degradation and conversion efficiency. The aim of theresearch was to get the composite flora which had effective function ondegradation of the straw, and explored the best conditions of their cultivation andthe kinetics in the fermentation process.First of all, cow dung, pig manure compost, corn soil, rotten wood and amixture of pig manure were used as the inoculum. Through the ChuanDaienrichment won five compound flora which could produce acid by Straw stalkfermentation namely FMc, FMd, FMs, FMw and FM（d+w）. Among themFM（d+w） had the highest total acids production of2.06g/L.Secondly, batch fermentation method was used to explore the most suitablenitrogen species of FM （d+w） flora and its amount for the fermentation. Theresults showed that1g/L was most suitable when peptone was used as thenitrogen source. In addition, pH8was optimum for this flora straw producedacids fermentation and explored the impact on the system of straw producedacids fermentation and the suitable concentration of Co²⁺and Zn²⁺, the two kindsof the trace elements. The results showed that0.024g/L Zn²⁺and0.012g/L Co²⁺was the best concentration.Finally, based on the optimal results of the tests above and Monod equationand Monod kinetic model, the rice straw hydrolysis fermentation model for theacid production was established. Moreover, the kinetic parameters of the modelwere got and the accuracy of the model was verified. The conclusion of this paper was not only to provide seed resources forusing microbial anaerobic fermentation of the straw in the future, but also make acontribution to the research of improving conversion efficiency of the resourcesof crops straw, which had a guiding significance and some theoretical value.