Preparation And Application Of Novel Biogas Fermentation Microbial Agent

China is an agricultural country which there is abundant straw resources. A large numberof straws can’t be reasonable utilized, which results in both resources loss and environmentpollution. Biogas fermentation of straw can effectively resolve this problem. However, it hascomplex supramolecular structure with cellulose, hemicellulose and lignin. Putting the strawinto fermenter directly limits the effect of degradation, for the waxy layer and lignin are notdamaged. This paper aims to screen many species of microorganisms from the naturalenvironment with evaluating the effect of degradation rate for lignocellulose. Then make thefiltered microorganisms into biogas fermentation microbial agents. And apply the agents to thestraw biogas fermentation process, study the influence of the agents for the process and theproducts.A variety of microorganisms are isolated from the methane fermentation broth, soil andcompost. Then the dominant ones are filtered through the analysis of degradation rate forlignocellulose、growth、enzyme activity and antagonistic experiments. After that, the dominantmicroorganisms are combined for groups. Dominant groups are selected with further screeningfor the highest enzyme activity. Then prepare of these microorganisms into the correspondingbiogas fermentation microbial agents. And put the straw pretreated by these agents intofermenter and find the optimal agent with contrasting the different gas productions. Finally, themicroorganisms in the agent picked out are identified. In addition, the fermentation products areresearched by nuclear magnetic resonance, scanning electron microscopy methods, X-raydiffraction and infrared spectroscopy; the components in anaerobic digestion effluent aredetermined with GC-MS and HPLC.The main conclusions are followed:(1) Ten kinds of the microorganisms are selected through screening, rescreening andantagonistic experiments. Moreover, four kinds of microorganisms are filtered for the enzymeactivity. No.12and8groups of microorganisms respectively show the highest cellulase activityand laccase activity,11.398U/mL and0.083U/mL. Then prepare of these four groups ofmicroorganisms into the corresponding biogas fermentation microbial preparation agents, putthe straw pretreated by the four agents into the gas tank for anaerobic fermentation at37℃. Itfinds that the gas production of No.6agent is the strongest during the30days,181%improvement over the blank. Finally, change the mass proportion of No.6agent and straw. It hasthe highest production at1:50, which is7369mL. Microbial identification shows that thereexist penicillium glaucum, rhizopus oryzae, white rot fungus, aspergillus flavus and snails sp inthe No.6agent.(2) Changes in the structure of straw during the biogas fermentation process are studied. It tells us that the crystallinity of cellulose changes from47.45%to21.38%. The FTIR imagesreveal the vibration intensity of each functional group gets weakened. When fermentation iscompleted, the vibration of aromatic ring, syringyl ring and guaiacyl ring increase.Meanwhilethe content of Cα、Cβ、Cγ （β-O-4）and-OCH3decrease in the anaerobic degradation process,part of syringyl and guaiacyl ring decompose. Scanning electron microscopy shows that thesurface of straw is gradually destroyed after the beginning of fermentation, the celluloseskeleton is tardily clear, microbes thrive in its interior, and finally the straw structure fracture.(3)In this paper, the components in anaerobic digestion effluent are investigated withGC-MS and HPLC. There exists a small amount of ethylbenzene,1,2,4-trimethyl-benzene and1,6-dimethyl-4-(1-methylethyl)-naphthalene in raw manure. After fermentation by mixingwith straw, ethylbenzene,1,2,4-trimethylbenzene,1,6-dimethyl-4-isopropyl-naphthalenegradually decrease and disappear, while generating a variety of other organic compounds,including propionic acid, butyric acid, valeric acid, phenol, catechol, p-methyl phenol, benzoicacid, phenylacetic acid, phenylpropionic acid,3-hydroxybenzoic acid,3-hydroxyphenylaceticacid,3-hydroxyphthalic acid and so on. The result of HPLC shows that the contents of threekinds of volatile fatty acids overall tend to increase during fermentation. Phenol’s content variesbetween0.07～0.48mg/L during the4weeks. Howecer, benzoic acid’s content is only0.0032mg/L after one week and falls down below the detection limit in the remaining time.