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玉米秸秆沼气发酵生物强化技术研究
其他题名
张洁
导师邱艳玲
2015-05
学位授予单位中国科学院研究生院
学位授予地点北京
学位专业生物化学与分子生物学
关键词厌氧发酵 甲烷 玉米秸秆 生物强化 木质素降解菌系
摘要农业废弃物秸秆,由于其产量丰富、生产成本低、较高的多糖含量和甲烷产量,一直被认为是具有广泛应用前景的厌氧发酵原料。然而,木质纤维素厌氧发酵产甲烷的效率却很低,这除了是由秸秆的复杂结构决定的之外;另一方面取决于厌氧发酵菌群的活性和稳定性。因此,优化微生物菌落结构、提高菌群活性对提高秸秆降解率和甲烷产率具有重要意义。生物强化技术是向原生境中投加具有某特定功能的菌株(群),以提高土著微生物群落处理能力的一种生物学方法,是一种有潜能且强有力的调节原环境菌群结构和代谢能力的方法。环境友好、节约能源且不需要任何化学物质的添加是生物强化工艺最显著的优点。将秸秆厌氧发酵技术和生物强化技术相结合,探究外源菌对秸秆厌氧发酵系统的强化作用,可以实现在低耗能、无污染、条件温和的反应过程中提高秸秆降解率和产能效率。本研究利用两种具有不同代谢能力的厌氧菌作为外源强化菌株,玉米秸秆作为底物,处理后的产甲烷沼液作为接种物,分别探究了其对玉米秸秆中温厌氧发酵产甲烷的强化作用。经过甲烷产量的测定,初步确定了乙酸型发酵细菌Acetobacteroides hydrogenigenes和芳香族化合物降解菌Sporotomaculum syntrophicum具有明显的强化作用;设置5%、10%和20%的强化菌接种比例,阐明了强化菌接种比例与强化效果之间的关系,确定了最适强化菌接种比例;通过测定玉米秸秆发酵前后各组分(纤维素、半纤维素和木质素)的含量变化及秸秆三大组分模式物的生物强化研究,阐明了强化菌提高玉米秸秆去除率和甲烷产量的作用机理。此外,为了促进木质素的降解,从不同环境中筛选的19种可能具有木质素降解潜能的样品作为初始驯化菌系,驯化能高效降解木质素产甲烷的厌氧菌系。本论文具体研究内容如下: 1. 以厌氧糖类发酵产氢产乙酸的拟杆菌门细菌Acetobacteroides hydrogenigenes作为研究对象,探究了其对玉米秸秆厌氧发酵的生物强化作用。A. hydrogenigenes生长周期短、具有较高的底物和产物耐受性,是一株具有较强强化潜能,能适应复杂发酵环境的微生物。A. hydrogenigenes使玉米秸秆厌氧发酵甲烷产量提高19-23%,当10%接种时,甲烷产量达到最大(258.1 mL/g-corn straw)。A. hydrogenigenes能使甲基纤维素和木聚糖的厌氧降解甲烷产率分别提高16.8%和7.0%。推测其最可能的强化机制为:A. hydrogenigenes将更多的木质纤维素生物质的水解产物,像五碳糖和六碳糖,转化为乙酸氢气,为产甲烷菌提供了更多底物的同时,促进了秸秆中纤维素和木聚糖的降解。 2. 以厌氧安息香酸降解菌Sporotomaculum syntrophicum 为研究对象,探究了其在玉米秸秆厌氧发酵产甲烷领域的应用价值。5-20%比例接种时,S. syntrophicum使玉米秸秆厌氧发酵甲烷产量提高了12-20%, 5%接种时,累积甲烷产量最高达到252.2 mL/g-TS;S. syntrophicum使秸秆中纤维素、半纤维素和木质素的去除率分别提高10-13%,3-5%和38%左右,且能提高羧甲基纤维素、木聚糖和碱木质素的厌氧发酵甲烷产率。其最可能的强化机制为:S. syntrophicum对原有产甲烷菌系具有调节作用,使发酵系统菌群更适应秸秆厌氧发酵系统,从而促进秸秆各组分的降解,进而提高甲烷产率。 3. 采用分别从不同环境中筛选的19种可能具有木质素降解潜能的样品作为初始驯化菌系,采用连续驯化培养的方法,以0.1%碱木质素作为底物,驯化能高效降解木质素产甲烷的厌氧菌系。经过两代驯化,保留了甲烷产量较高的10组秸秆驯化体系。其中来自于稻田土壤的样品甲烷产量为136.1 mL/g-lignin,木质素降解率为9.9%,是目前获得的最好的驯化体系。对其进行进一步研究确定其各项性质之后,以期将其应用于秸秆厌氧发酵,提高秸秆中木质素的去除率。
其他摘要Agricultural residues are attractive and potential feedstock for anaerobic digestion due to its abundance, low production costs, high polysaccharide content and methane yield. However, the efficiency of converting lignocellulosic biomass into methane is limited, which is attributed to not only the complex structure of corn straw but also the low activity and stability of the anaerobic microbial populations. So it is significative to pay attention to design and optimize the complex microbial consortia. Bioaugmentation is a technology for improving the removal of undesired compounds by introduction of specific competent strains or consortia. The basic premise for this intervention is that the metabolic capacities of the indigenous microbial community already present in the biotope slated for cleanup will be increased by an exogenously enhanced genetic diversity. Environmental friendly, energy saving and no any chemicals addition are the significant advantages of bioaugmentation. The method, application the bioaugmentation technology into the anaerobic digestion of straw, could accelerate the degradation of straw and improve production efficiency in condition of low consumption, no pollution and mild environment. This study mainly focused on the effect of the two exogenous, anaerobic enhanced bacteria on the mesophilic, methanogenic, anaerobic fermentation of untreated corn straw. Hydrogen producing acetate-type bacterium Acetobacteroides hydrogenigenes and benzoic acid degrading bacterium Sporotomaculum syntrophicum were found to have the bioaugmentation potential, according to the cumulative methane production. Then, the optimum inoculation ratios of the bacteria were determined through setting different inoculation ratios (5%, 10% and 20%). To investigate the functional mechanism of the enhanced bacteria on the degradation of corn straw, on the one hand, the composition of corn straw before and after digestion were studied, on the other hand, effect of the bacteria on anaerobic degradation of methyl cellulose, kraft lignin and xylan models were measured. Besides, nineteen types of environmental samples, which may have the potential for lignin degradation, were chosen as the initial system to domesticate efficient anaerobic lignin-degrading consortia. Details are as follows. 1. The bioaugmentation effect of Bacteroidetes bacterium A. hydrogenigenes on anaerobic digestion of corn straw was studied. A. hydrogenigenes is a hydrogen-producing acetate-type bacterium with a wide range of growth, substrate utilization, relatively high growth rate, high hydrogen yields, substrates and products tolerance. Bioaugmentation with A. hydrogenigenes could increase 19–23% methane yield from corn straw degradation. The maximum methane yield was 258.1 mL/g-corn straw with 10% inoculation. A. hydrogenigenes could improve the methane yields from methyl cellulose and xylan (models for cellulose and hemicelluloses, respectively) by 16.8% and 7.0%, respectively. A proposed mechanism is that A. hydrogenigenes promotes more hydrolysates of lignocellulosic biomass, such as C5 and C6 sugars to acetate and hydrogen. As a result, it provides a source of energy for the methanogens. 2. The bioaugmentation effect of benzoic acid degrading bacterium Sporotomaculum syntrophicum on corn straw anaerobic fermentation was investigated. S. syntrophicum in 5-20% inoculation ratios could improve the methane yield by 12-20%. The maximum methane yield was 252.2 mL/g-corn straw with 5% inoculation. S. syntrophicum increased not only the degradation efficiency of cellulose, hemicelluloses and lignin of corn straw by 10-13%, 3-5% and 38%, respectively, but also the methane production from methyl cellulose, xylan and kraft lignin models. A proposed mechanism is that S. syntrophicum could regulate the structure and activity of the indigenous flora, making it more adapt to fermentative environment. 3. Nineteen types of environmental samples, which may have lignin-degrading potential, were chosen as the initial system to domesticate efficient anaerobic lignin-degrading consortia with 0.1% (m/v) kraft lignin as the sole substrate. After two generations of culture, the culture from rice soil was the best among the remaining ten samples. It’s methane yield was 136.1 mL/g-lignin, and the kraft lignin degradation rate reached 9.9%. The characteristics of the culture will be determined in the next step. It hopes that apply the culture to the corn straw anaerobic fermentation system in order to increase the degradation of lignin.
作者部门生物制氢与沼气团队
学科领域生物制氢与沼气
公开日期2018-09
学位类型硕士 ; 学位论文
语种中文
文献类型学位论文
条目标识符http://ir.qibebt.ac.cn/handle/337004/8107
专题工业生物燃气研究组
作者单位中科院青岛生物能源与过程研究所
推荐引用方式
GB/T 7714
张洁. 玉米秸秆沼气发酵生物强化技术研究[D]. 北京. 中国科学院研究生院,2015.
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