秸秆沼气厌氧发酵中纤维素分解的微生态解析

lignocellulose are abundance in straw, however, they can not be utilized fullly because of difficulty to degrade rapidly. The research found that a community with a good symbiotic relationship has strong straw lignocellulose degrading activity than a single strain. To reveal the multi-bacteria symbiotic relationship and the mechanism of this symbiotic relationship to promote straw rapid degradation can goes on with positive theoretical exploration for further improving the efficiency of straw decomposition and breaking through the bottleneck of lignocellulosic materials bio-transformation fastly. And this rearch has great theoretical value and appllicaton prospct to drive efficient straw biogas industrial development and developing ralated new technologies. In the previous study, we have enriched an efficient and stable straw-degrading bacterial community already, a cellulolytic bacterial Clostridium thermocellum CTL-6, and its symbiotic bacterial from this community were isolated, the relationship of promoting and inhibiting between bacteria based on metabolites (organic acids, sugar, etc.) were investigated by combination and co-cultivation methods of the strains. To explore the role and econiche of the strains during the process of the straw decomposition by stable isotope probing (SIP) technique; to examine the effcte of metabolites (organic acids) of symbiotic bacteria on structure of straw material by microscopy technique. Finally, from the view of micro-ecological, revealling mechanism of multi-bacterial symbiotic relationship and its promoting rapid acidification degradation of straw.

秸秆含有丰富的木质纤维素，因其难以快速分解而未被充分利用。目前已发现，具有良好共生关系的菌群比单菌具有更好的秸秆纤维素分解活性。揭示这种多菌共生关系及其促进秸秆快速分解的机理，可为进一步提高秸秆分解酸化效率，突破木质纤维素材料难以快速生物转化的瓶颈进行积极的理论探索，对推进高效秸秆沼气产业化发展及相关新技术开发具有重大的理论价值和应用前景。本研究在已获得一组高效、稳定小麦秸秆快速分解菌群WDC2的基础上，分离并获得菌群内纤维素分解菌株Clostridium thermocellum CTL-6及相关共生菌株，通过菌株组合共培养的方法，研究基于代谢产物（有机酸、糖等）的菌间促进与抑制关系；采用稳定同位素探针技术（SIP），探索秸秆分解过程中各菌株的作用及生态位；利用显微技术考察共生菌代谢产物对秸秆物质结构的影响。最终从微生态角度，揭示秸秆沼气生物转化过程中，纤维素快速分解机理。

木质纤维素难以快速分解是限制木质纤维素利用的一个瓶颈。而菌群相比于单菌具有更好的纤维素分解活性和环境适应性。本项目以探索微生物菌群内协同降解纤维素的机理为目的，在富集纤维素快速分解产甲烷菌群的基础上，分离功能菌株，构建菌株组合，探索组合内纤维素分解的微生态机理。.项目成功富集并获得一组厌氧消化产甲烷菌群。该菌群具有较好的分解木质纤维素产甲烷能力。可将50g油菜干秸秆厌氧消化产生沼气，产气效率为264 mL /g，黄姜废渣厌氧消化的产气效率为855 mL/g。该菌群在5%的秸秆加载量具有最高的产气效率为342.2 mL/ g。.分离该菌群内的主要优势菌株，获得Bacillus licheniformis Ba2，Aneurinibacillus thermoaerophilus Ba3、Ba5，Sulfate reducing bacteria CTS，Bacillus solfatarensis YW4等菌株。将获得的菌株与Clostridium thermocellum CTL-6共培养，构建一系列具有纤维素分解能力的菌株组合。其中Ba2+CTL-6+Ba5、Ba2+CTL-6+CTS组合具有较好的滤纸分解活性。.组合中，Ba2能有效促进CTL-6在PCS培养液中的纤维素分解活性。9天Ba2+CTL-6组合滤纸分解率达93.2%，分解滤纸纤维素过程中pH呈碱性变化。将其与呈酸性变化的Ba5+CTL-6进行再组合后，获得的复合菌系Ba2+CTL-6+Ba5，其纤维素分解能力相比之前两个组合有了显著提升。表明“酸碱互补”的菌系组合原则可进一步获得功能强化菌系。Ba2菌株可提升菌系纤维素分解能力，有助于增强菌系中CTL-6产纤维素酶的代谢活动。菌株胞外总蛋白分泌大，影响菌系的丙酸和丁酸的代谢。.与此相对，Ba2+CTL-6+CTS组合培养7天的滤纸分解率为61.8%。CTS菌株影响菌系内乳酸、甲酸、丙酸、丁酸的代谢，可能对Ba2菌株的代谢活动存在一定的抑制作用。菌株CTS具有还原SO42-的能力，革兰氏染色为阴性，最适生长温度为50℃，最适生长pH为7.0～7.5。.本项目的研究对构建快速分解木制纤维素转化为甲烷的功能菌群开发，提高对木质纤维素类物质的综合利用技术应用有指导意义。