| 摘要 | Straw biogas technology can not only produces clean energy, but also make full use of agricultural residues and provide a basis for environmental protection and sustainable development. Because of high amounts of cellulose, hemicellulose, and lignin and its wax layer structure, which makes crop straw decomposition process very slowly and technical problems still existed. The research on anaerobic corn straw degrading microbial community is of significance to understand the essential of corn straw degradation and improve the degradation rate and gas production. The general pattern of corn straw biogas reactor was co-digestion of silage corn straw with other wastes, hoverer, there is no full-scale biogas reactor used the corn straw as the sole feedstock. In addition, the knowledge of the microbial community involved in anaerobic digestion system for the treatment of crop residues is still limited.To get a grasp of the microbial communities in anaerobic corn straw degrading microbial systems, methanogenic corn stalk degrading enrichment cultures were constructed using corn stalk as the sole carbon source and eight types of environmental samples such as rice, corn, wheat soils and reed swamp as inocula. Combined methane production, volatile acids, pH and microbial communities, we found fermentative heterotrophs were the major bacterial community and microbial community structure and fermentation pH has a corresponding relationship: bacterial diversity was higher in cultures with neutral pH than those with acidic pH. Overall, clones affiliated with the phylum Firmicutes and Bacteroidetes were the most frequently and commonly observed in cultures with acidic pH. To get deep insights into microbial communities involved in full-scale reactor treating corn straw, anaerobic biogas slurry was taken from a full-scale mesophilic (35°C), anaerobic completely stirred tank reactor (CSTR) (volume, 500 liters) constructed in China. Corn straw biogas slurry showed high specific methane yield and TS removal rate, suggesting crop residues are promising alternative feedstocks for biogas production. During anaerobic degradation of corn straw, volatile acids and aromatic compounds (p-cresol, phenylpropionate, phenol and benzoate) were detected as transient intermediates, indicating lignin could decomposed under anaerobic condition. Phylogenetic analysis indicated biogas slurry showed higher microbial diversity and more complex community structure. Fermentative heterotrophs were the predominant bacterial community. On basis of knowledge on dominant functional microbial groups, the biotechnological intensification of biogas production was studied by adding various microbes to hydrolytic and fermentative, acetogenic and methanogenic stages of straw degradation, respectively. The results showed that methane increased 30% upon addition of syntrophic bacterial groups, hydrogenotrophic methanogens and aceticlastic methanogens, and the optimum inoculum size (10%) was estibalished for corn straw degrading microbial system. |
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