氮源对玉米秸秆沼气发酵过程及微生物群落的影响

发布时间：2018-05-26 13:19

本文选题：玉米秸秆 + 沼气发酵　；参考：《黑龙江八一农垦大学》2017年硕士论文

【摘要】：我国玉米秸秆产量巨大但资源化利用程度低。以秸秆为原料的沼气发酵工艺产气率不高。本研究通过优化玉米秸秆沼气发酵的氮源种类和浓度,提高秸秆沼气发酵的产气量。通过分析发酵料液中微生物多样性和丰度变化规律,从微生物学角度揭示氮源对玉米秸秆沼气发酵效率的影响。本研究以玉米秸秆为沼气发酵原料,选择有机氮源尿素和无机氮源硝酸铵为外加氮源,添加浓度分别为0 g/L(对照)、1 g/L、2 g/L、4 g/L进行批次试验,发酵时间30d。试验结果表明,氮源添加尿素1 g/L的处理产甲烷效率最高,TS甲烷产率为217.5 m L/g。选取添加尿素1 g/L这一浓度在25L反应器中进行连续进料的玉米秸秆沼气发酵试验,结果发现:加尿素的处理的TS甲烷产率显著高于不加氮的对照,而且产气高峰更加提前。加氮较不加氮处理能显著提高纤维素和半纤维素的降解率,但木质素降解率差异性不显著。利用高通量测序技术研究玉米秸秆沼气发酵样品中微生物多样性及其变化规律,结果表明,氮素添加能够显著影响发酵料液中细菌多样性,但没有显著影响古菌多样性。氮素添加能够显著影响细菌和古菌的菌群丰度。在各发酵时期的样品中,细菌优势菌群(菌群丰度大于9%)有Bacteroidetes(拟杆菌门)(22.5%-43.4%)、Firmicutes(厚壁菌门)(18.1%-36.6%)、Spirochaetes(螺旋菌门)(5.2%-14.1%)、Proteobacteria(变形菌门)(2.2%-11.1%)、Chloroflexi(绿弯菌门)(0.7%-9.1%)等。在发酵初期(10d),添加氮处理Bacteroidetes的数量低于对照,所有处理Spirochaetes的数量高于对照。在属水平上,各发酵时期菌属组成均不相同。各发酵时期料液中优势古菌类群(菌群丰度大于4%)有Methanosaeta(甲烷鬃毛菌)(36.7%-68.7%)、Methanoculleus(甲烷囊菌属)(3.8%-16.2%)、Methanospirillum(甲烷螺菌属)(5.2%-9.2%)、Methanobacterium(甲烷杆菌属)(1.5%-14.3%)和Methanosarcina(甲烷八叠球菌属)(0.6%-4.9%)。发酵初期(10d),添加氮处理的Methanosaeta数量低于对照,处理的Methanoculleus的数量高于对照。随着发酵的进行,对照的Methanobacterium丰度逐渐提升。细菌比古菌表现出更加复杂的多样性。选取氮素添加量为1 g/L的处理发酵初期样品进行宏基因组学研究,结果共获得72.37%的细菌和18.52%的古菌注释序列,其中的优势菌群主要参与脂肪、蛋白质和纤维素等大分子有机物降解。功能基因注释结果表明体系内存在食氢和食乙酸两种产甲烷途径,其中食氢产甲烷途径占据主导地位。注释到的Sphaerochaeta在体系中大量存在,揭示其在玉米秸秆降解产甲烷环境中具有重要作用。综上所述,以玉米秸秆为原料的沼气发酵时,适当的添加氮源能够显著提高玉米秸秆的TS甲烷产率;氮素添加能够显著影响发酵料液中细菌组成多样性,但没有显著影响古菌组成多样性,且能够显著影响细菌和古菌的菌群丰度;通过研究不同氮源及浓度对玉米秸秆沼气发酵的影响,能为提高玉米秸秆甲烷产率,提高秸秆类生物质资源化利用提供理论指导。
[Abstract]:The yield of corn stalks in China is huge but the utilization of resources is low. The biogas production rate of the biogas fermentation process with straw as raw material is not high. This study improves the biomass of straw biogas fermentation by optimizing the variety and concentration of nitrogen source of the corn straw biogas fermentation. The study revealed the effect of nitrogen source on the efficiency of corn straw biogas fermentation. This study took corn straw as the biogas fermentation material, selected the organic nitrogen source urea and the inorganic nitrogen source ammonium nitrate as the external nitrogen source. The addition concentration was 0 g/L (control), 1 g/L, 2 g/L, 4 g/L for batch test. The fermentation time 30D. test results showed that the nitrogen source added urea 1. The methanogenic efficiency of g/L was the highest, the yield of TS methane was 217.5 m L/g. and the concentration of 1 g/L added urea was selected as a continuous feed of corn straw biogas fermentation in 25L reactor. The results showed that the methane yield of TS treated with urea was significantly higher than that of non nitrogen control, and the peak of gas production was more advanced. The degradation rate of cellulose and hemicellulose could be significantly improved, but the difference of lignin degradation rate was not significant. The microbial diversity and its variation in the corn straw biogas fermentation samples were studied by high throughput sequencing. The results showed that the nitrogen addition could significantly affect the diversity of bacteria in the fermentation broth, but there was no significant influence on the ancient times. Microbial diversity. Nitrogen addition can significantly affect the abundance of bacterial and paleobacteria. In the fermentation period, the dominant bacterial flora (bacterial abundance greater than 9%) has Bacteroidetes (22.5%-43.4%), Firmicutes (18.1%-36.6%), Spirochaetes (5.2%-14.1%), Proteobacteria (2.2%). -11.1%), Chloroflexi (0.7%-9.1%) and so on. At the initial stage of fermentation (10d), the number of Bacteroidetes in the treatment of Bacteroidetes was lower than that of the control, and the number of all Spirochaetes was higher than that of the control. At the level of the fermentation, the composition of the bacteria was different at the fermenting period. The colony of predominant bacteria in the fermentation period (more than 4% of the abundance of bacteria) was Methanosaet A (36.7%-68.7%), Methanoculleus (Methanococcus) (3.8%-16.2%), Methanospirillum (methanobacteria) (5.2%-9.2%), Methanobacterium (methanobacteria) (1.5%-14.3%) and Methanosarcina (Methanococcus eight) (0.6% -4.9%). At the initial stage of fermentation (10d), the number of Methanosaeta to be treated with nitrogen is lower than that of the control. The number of noculleus was higher than that of the control. With the fermentation, the abundances of the control Methanobacterium increased gradually. The bacteria showed a more complex diversity than the ancient bacteria. A total of 1 g/L of nitrogen added to the treatment of the initial fermentation samples was studied by macrogenomics, and 72.37% of the bacteria and 18.52% of the archaeal annotation sequences were obtained. The dominant flora mainly participates in the degradation of large molecular organic compounds such as fat, protein and cellulose. The results of functional gene annotation show that the system is stored in the two methanogenic pathways of hydrogen feeding and acetic acid, of which the hydrogen producing methanogenic pathway occupies the dominant position. The annotated Sphaerochaeta exists in the system, revealing its degradation production in corn straw. In the methane environment, the proper addition of nitrogen source can significantly increase the TS methane yield of corn straw when the corn straw is used as the raw material. Nitrogen addition can significantly affect the diversity of bacterial composition in the fermentation broth, but it has no significant influence on the diversity of the paleobium, and it can significantly affect the bacteria and the bacteria. The effect of different nitrogen sources and concentration on the biogas fermentation of corn straw can provide theoretical guidance for improving the methane yield of corn straw and improving the utilization of straw biomass.
【学位授予单位】：黑龙江八一农垦大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S216.4

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