Isolation And Chraterization Of Anaerobic Cellulolytic Microorganism For Butanol Production

Butanol is regard as a new generation of fuel which is similar to gasoline inproperties such as energy density, and could be applied to petrol and diesel enginewithout any transformation, moreover, no pollutants such as sulfur oxide andnitrogen oxides are emitted, so butanol is considered to be one of the mostpromising fuel in the coming future. While biomass is one of the most abundantrenewable resources in the world, most biomass is synthesized throughphotosynthesis by plants, a great number of crop straw is produced in China eachyear, but most of the crop straw is not made the most use of. If certain techniquehelps to convert these biomass resources into butanol, this must greatly reduce thecost of butanol production, making it possible to produce butanol in a large scale,which helps to solve the energy shortage problem in a certain extent.This study is dedicate to screening microorganism and mixed microbialcommunity which able to degrade cellulose under anaerobic and mesophiliccondition, then working together with butanol prodution strain to construct aco-culture system converting cellulose into butanol. At the very beginning of theenrichment culture, bacteria samples were collected from fresh cow dung, andculturing generation after generation as domestication, a mixed microbialcommunity numbered N3was isolated which able to degrade cellulose efficiently,after culturing in cellulose culture media for5days, the degradative rate forcellulose reach to63.35%. Culturing in a system which cellulose is the sole carbonsource, five pure strain have been isolated from the N3mixed microbial community,and marked N3-1, N3-2, N3-3, N3-4and N3-5respectively. Among these fivestrains, strain N3-2show much better than other four stains in cellulose degradation,identification of strain N3-2shows that the bacteria is gram-positive, spore forming,and ferments cellulose, xylose etc., further characterization of strain N3-2bysequence alignment of16S rDNA showed that strain N3-2share99%similarity withClostridium celevecrescens in max ident. According to the morphological of strainN3-2and physiological&biochemical that have been detected, and the position ofstrain N3-2in phylogenetic tree, confirming that strain N3-2belongs to C.celevecrescens.By comparing the cellulose degradation efficiency of N3mixed microbialcommunity with five pure strain that have been isolated and the recombinationmicrobial community, the N3mixed microbial community performs very muchbetter than any other strains that have been isolated and the recombination microbialcommunity in cellulose degradation, therefore, it is chosen to degrade cellulose in the co-culture system, by fermenting cellulose and turning it into small molecularsugars, supporting butanol production strain growing in the system, the wholesystem finally convert cellulose into butanol. To optimize the condition ofco-culture system for butanol production, experiment of different factor that affectthe co-culture system have been conducted, the result shows that under the conditionof innoculation of butanol production strain C. acetobutylicum ATCC824after N3mixed microbial community culturing for48hours or more, initial pH adjust to7,and addition of cellulose over20g/L, plenty of innoculation of both strains, theco-culture system produce butanol the most.Despite the amount of butanol production in our co-culture system still do notmeets the need of industrialization, this study prove that it is possible to convertcellulose into butanol under anaerobic and mesophilic condition, by combiningdifferent microorganism working together in one culturing system, which lay afoundation for the follow-up study of efficiently converting cellulose into butanol.