Construction Of Co-culture System For Enhanced Butanol Production And Utilization Of Rice Straw For Producing Biobutanol

To alleviate the negative impacts of environment pollution and the lack of fossil fuel,it's urgent to develop renewable energy.Butanol is an excellent bioenergy and the production of biobutanol is the research hotspot currently.There are some problems during the fermentation process of butanol-producing: the phenomenon of “acid-crash”,low substrate utilization efficiency and low production of butanol,there is an urgent need to establish a regulatory approach that will increase the solvents production based on a stable fermentation process.In addition,the high cost of fermentation substrates is also a major factor limiting the development of bio-butanol industrialization.Rice straw is a well-stocked lignocellulosic material,but its structure is difficult to be degraded.How to develop a method for efficient degradation of rice straw and achieve effective bio-butanol conversion is an effective way to reduce the cost of butanol producing,also meets the needs of the low-carbon development strategy.In this study,Saccharomyces cerevisiae and Clostridium beijerinckii co-culture system was constructed using the characteristics of Saccharomyces cerevisiae which can secrete extracellular amino acids beneficial to butanol synthesis under environmental stress.On this basis,a high-efficiency,low-cost preparation method of rice straw was established,and a well-established co-culture system was used for butanol fermentation to achieve efficient utilization of rice straw for producing biobutanol.The research results obtained in this research mainly include the following aspects:In this study,the inoculation time,ratio and initial pH of Clostridium beijerinckii/Saccharomyces cerevisiae co-culture system were optimized.Saccharomyces cerevisiae was added after 12 h fermentation of Clostridium beijerinckii,the inoculation of yeast was 2%,and the pH was 7,butanol production reached 12.75 g/L,an increased 203% compared to the fermentation system of Clostridium beijerinckii.The metabolic mechanism of co-culture system was initially analyzed,extracellular secretion of amino acids(alanine,methionine,leucine,tyrosine,phenylalanine,lysine,arginine,valine)by Saccharomyces cerevisiae effectively increased the yield of butanol.Combining with the climate characteristics of the Northeast of China,the rice straw was pretreated with-15? NaOH/Urea solution,and the lignin removal rate reached 79%,however,cellulose and hemicellulose lost only 4.2% and 14.5%.Hydrolyzed rice straw with crude enzyme,pre-treated straw yielded higher glucose compared with untreated rice straw,under the crude enzyme hydrolysis conditions,the glucose content obtained per 100 g straw was 32.04 g,the straw saccharification rates were 46.3%.Using straw hydrolysis solution as a substrate,butanol fermentation was conducted with the co-culture system constructed in this experiment.When the pretreated rice straw was used as the substrate,the butanol yield by the co-culture system reached 10.62 g/L,increased by 151.7% compared with the single fermentation system of Clostridium beijerinckii F-6.In terms of substrate conversion efficiency,the co-culture system had higher substrate butanol conversion efficiency,and the butanol yield and ABE total solvent yield were 0.29 g/g and 0.40 g/g,respectively,compared to the Clostridium beijerinckii F-6 fermentation system increased by 123% and 122.2% respectively.