Study On Biogas Fermentation With Straw Pretreated By Microbial Agent

Methane is renewable clean energy and ecological energy. Poultry and animalfeces is the main raw material of biogas production in our country, but poultry andanimal feces far cannot satisfy the methane fermentation raw material shortage. Strawresources are rich in our country, which can make up the deficiency of poultry andanimal feces fermentation raw materials. Because straw contains difficult degradationcomposition—lignin and cellulose, we must carry onthe pretreatment before using it.This research is aimed at straw difficult degradation composition, screening efficientfunction bacteria, constructing the straw pretreatment functional bacteria agent, so asto speed up the decomposition speed of the refractory material, increasing themethane production.With corn straw as the matrix for solid state culture, through the determination ofstraw lignin、cellulose、hemicelluloses degradation rate and lignin、cellulose enzymeactivity change, screening straw pretreatment target bacteria from laboratorypreservation strains and litter、landfill site acquisition mixed samples, finally7strainsof target bacteria were obtained:1strain of mixed bacteria,2strains of fungi,2strainsof actinomycetes,1strains of bacteria,1strain of Trichoderma viride. Through theantagonistic experiment, there was no antagonism between seven strains.Seven strainswere divided into four types, there were9sets of different proportion through usingorthogonal assistant software. The straw was pretreated6days with different ratio ofcomposite bacteria agent. Straw weightlessness and lignin、cellulose、 hemicellulosecontent change were measured after6days, with straw as raw material of biogasfermentation, according to the gas results determine the best ratio of bacteria agent.The landfill site samples and litter mixed samples were cultivated under50℃and35℃, two groups of different temperature of mixed bacteria were obtained. Study ofmixed bacteria on filter paper degradation in7days and on the degradation of straw in30days. The results show that: The weight loss rate of straw, the degradation oflignin、cellulose and hemicelluloses, lignin enzyme activity and cellulose enzymeactivity were higher at50℃than at35℃, so the high temperature mixed bacteria wasas a target bacteria. At50℃, the filter weight loss rate was76.2%after7days.The straw weight loss rate was34.23%after30days, and the lignin、 cellulose、hemicellulose degradation rate of straw was56.36%、42.88%、62.77%, respectively.Lignin activity and cellulase activity reached the highest after15days at50℃, Lacactivity、CMCase activity and FPA activity was10.2U/g、5.7U/g、3.2U/g,respectively. Cellulase activity reached the highest when the microcrystallinecellulose was carbon source and pH was7, CMCase activity and FPA activity was690U/L and360U/L, respectively.Fungi were two strains: HX-1, YJ-1-1. Firstly screening3strains betterdegradation effect from laboratory preservation6strains of bacteria, the two twohybrid, and finally determined two strains of fungi: HX-1, YJ-1-1. The degradationeffect of mixing fungi was better than Single strain. The straw weight loss rate was28.54%, the lignin、cellulose、hemicellulose degradation rate of straw was42.57%、34%、60.45%, respectively. Lac activity was10.9U/g, cellulose enzyme activity wasvery low.Actinomycetes were two strains: Q0,2-9. The degradation effect of mixingactinomycetes was better than single strain. The straw weight loss rate was27.56%,the lignin、cellulose、hemicellulose degradation rate of straw was30.37%、36.64%、56.67%,respectively. CMCase activity and FPA activity was5.5U/g、3U/g,respectively, lignin enzyme activity is very low.Another two strains were1strain of bacteria and1strain of trichoderma viridewhich were preserved in laboratory. Finally7strains of target bacteria were obtained,through the antagonistic experiment, there was no antagonism between seven strains.Seven strains were divided into four types, there were9sets of different proportionthrough using orthogonal assistant software. The straw was pretreated with differentratio of composite bacteria agent, then straw weightlessness and the degradation oflignin、cellulose、 hemicellulose of the fourth group were highest. But the biogasproduction of the ninth group was best, which showed that degradation effect of strawwas not necessarily good gas generation effect, maybe the cause of excessiveconsumption materials. The cumulative gas production of the ninth group strawpretreated by microbial agent was highest. The cumulative gas production was8481mL, which was33.05%higher than straw without microbial agent pretreatment.The cumulative CH4production of the ninth group straws was4795mL,which was37.83%higher than control group. According to the gas effect, the bestratio was the ninth group:3:3:2:1.