微好氧菌群强化分解木质纤维素及其提高甲烷产量的机理研究

The bottleneck of efficient methane production from straw is difficult to decompose lignocellulose rapidly during anaerobic digestion. The previous researches showed that the most of bacterial communities with the high decomposition ability of lignocellulose grew in microaerobic condition. Therefore, to reveal the mechanism of efficient decomposition and transformation of lignocellulose to produce methane by the microaerobic bacterial community, in order to further improving the utilization efficiency of straw and breaking through the bottleneck of fast bio-transformation of natural lignocellulosic materials during anaerobic digestion. Furthermore, this research has great throretical value and application prospect in developing related new technologies of accelerating methane production efficiency from straw. In this project, based on successful building the integrated two-division anaerobic digestion system to produce methane from lignocellulose in previous research, to screen and a cluster of acclimate a microaerobic bacterial community with the ability of efficiency decomposing lignocelluloses by adjusting oxygen concentration of hydrolysis and acidification division upside of reactor, and to analyze the key strains of flora which play important role in decomposition and transformation of lignocellulose, and then to evaluate the performances of the flora decomposing different lignocellulosic materials. In addition, to explore substance metabolism process and functions of the key strains during decomposing lignocellulose by the stable isotopic probing technique (SIP), and to investigate the ecological relationships among strains with different aerobism and metabolic function. Finally , to reveal the mechanism of rapid decomposing lignocellulose and efficient methane production by microaerobic bacterial community from the view of microbial ecology.

木质纤维素在厌氧发酵中难以快速分解是限制秸秆高效产甲烷的瓶颈。研究发现，能高效分解木质纤维素的微生物大多数属于微好氧菌群。在厌氧发酵体系中，揭示微好氧菌群对木质纤维素高效分解、转化和产甲烷的机理，可为进一步提高秸秆利用效率，突破天然木质纤维素难以快速生物转化的瓶颈进行积极的理论探索，对加速秸秆高效产甲烷新技术的开发具有重要理论价值和应用前景。本项目在已成功构建木质纤维素“分区一体”产甲烷体系的基础上，通过调控反应器上部水解酸化区的氧浓度，筛选、驯化一组能高效分解木质纤维素的微好氧菌群，研究菌群对不同结构木质纤维素的分解性能，分析该菌群中对木质纤维素分解、转化起主要作用的关键菌株；采用稳定同位素探针技术，在分区产甲烷过程中探索木质纤维素物质代谢流程和各功能菌株的作用；采用荧光显微镜技术考察不同需氧性和代谢功能菌株之间的生态关系。最终从微生态角度，揭示微好氧菌群快速分解秸秆和高效产甲烷的机理。

高含固率木质纤维素厌氧发酵工艺因能解决传统低含固率产甲烷技术的诸多缺点而受到全球关注，但由于物料分解效率低严重阻碍了该技术的广泛应用。强化微好氧菌群活性进而提高物料的分解效率是突破高含固率纤维质物料产甲烷效率低的重要手段。研究以提高粪秸高含固率厌氧产甲烷效率为目标，以油菜秸秆和牛粪为原料，在构建的“分区一体”连续产甲烷体系中，通过进料氧浓度、搅拌强度和有机负荷的调控，提高反应器上部“水解酸化功能区”中微好氧菌群活性，比较不同调控参数下微生物多样性、发酵物料理化性质和甲烷产率，阐明微好氧菌群在粪秸高效产甲烷体系中促进木质纤维素分解的机制。重点从功能性菌群时空的共生关系评价微好氧菌群提高粪秸产甲烷效率的调控有效性及其代谢机制。获得如下研究结果：（1）在含固率为15%、有机负荷为20g VS/L/d、搅拌强度为8 rpm、通氧量为3～5 mL/g VS的条件下，反应器中发酵物料可形成稳定的上部水解酸化和下部产甲烷的功能分区，容积产甲烷效率最高可达1.55L/L/d；（2）微好氧条件可加快半纤维素分解速率和提高乳酸的浓度，进而促进木质纤维素物料的分解和提高产甲烷速率，纤维素和半纤维素的分解效率分别可达28%和33%；（3）在微好氧条件下，水解酸化区细菌群中的关键菌株Acinetobacter、Lactococcus、Lactobacillus和Clostridium与产甲烷古菌群中的嗜氢型Methanobacteriale 和 Methanomicrobiales协同提高了木质纤维素物料的转化效率；（4）筛选出的微好氧产甲烷复合菌系MMC3稳定性良好，可使木质纤维素的分解效率达到40%以上；（5）在同一高含固率产甲烷体系中，通过微好氧调控强化水解酸化细菌群和产甲烷古菌群代谢环境的相对独立性有利于提高木质纤维素的分解。上述研究结果对深入认识木质纤维素高效产甲烷体系中不同代谢功能微生物群的相互关系具有重要意义，对研发木质纤维素高效产甲烷技术具有重要应用价值。