玉米秸秆低温高效降解复合菌系GF-20的关键功能菌及其低温降解生理机制研究

The cool climate limits efficiency decomposition of returning straw in spring maize region of north China is urgent problems in theoretical and technical area. In order to promoting efficient degradation of corn stover in low temperature regions, the before study a microbial consortium with efficient corn stover degradation ability at low temperature (the stover degradation ratio was 32% under 10℃ cultivation condition) was screened out by restrictive cultivation and cold acclimation and then it’s growth characteristics, diversity of microbial composition and stability were identified. Our present study takes clarifying the microbial composition structure of consortia GF-20 and it’s intertwined interspecies relationships as the breakthrough point, to further improve the corn stover degradation efficiency. Composite microbial system GF-20 was continuously subcultured under 10℃, the temporal-spatial succession of microbial community structure will be determined, and the key functional strains will be recombinant by "knock out" method, and its stability and the straw degradation efficiency will be tested so as to untangle the microbial synergistic network relationships between the strains of microbial consortium GF-20, furthermore, the physiological mechanism of the degradation of corn stover with high efficiency under low temperature will be evaluated. The result of this research will provide theoretical and technical supports for further explore ways of construction more efficient degradation microbial community.

立足于我国北方春玉米区低温限制还田玉米秸秆当季高效腐解的实际问题与技术需求，在课题组筛选驯化获得的玉米秸秆低温高效降解复合菌系GF-20（10℃，降解率32%）的基础上，针对进一步提高其玉米秸秆降解效率的核心问题，以揭示GF-20微生物组成结构为切入点，以明确其菌种间协同关系为突破，研究GF-20降解玉米秸秆微生物群落结构时空演替规律，并分离纯化单菌株，复配功能单菌，检测其稳定性和秸秆降解效率等，利用“Knock out”设计明确各菌种间的互作关系，揭示GF-20玉米秸秆低温高效降解生理机制，构建菌种模型，为进一步探索组配低温高效玉米秸秆降解复合菌系提供理论支持。

秸秆的生物降解具有高效率和环保等特点而备受关注。项目立足于内蒙古等北方寒旱区玉米秸秆还田当季降解难的技术需求和生产实际问题，开展玉米秸秆降解复合菌系GF-20降解效果、功能稳定性、协同关系、作用机理等研究，并分离纯化功能单菌、优化组合，获得复配菌提高降解效率。主要结果如下：（1）复合菌系GF-20在不同降解时期存在微生物群落结构演替，组成菌种类和丰度不断变化，关键降解物种 Pseudomonas、Dysgonomonas、Achromobacter、Stenotrophomonas、Cellvibrio 、Cellulomonas、Flavobacterium等协同降解木质纤维素，代谢方式主要为碳水化合物及氨基酸代谢，同时具有信号传导、细胞转运等多种代谢方式，编码较完整的纤维素和半纤维素降解酶系；（2）在温度4℃～30℃、pH值6.0～9.0条件下可保持良好的性质、功能与组成稳定性，碳源为玉米秸秆、氮源为硫酸铵和尿素(0.16%+0.04%)时复合菌系GF-20菌种组成更稳定，诱导复合菌系产纤维素酶，促进底物分解；（3）从GF-20中分离获得关键单菌株Achromobacter deleyi(A3)和Pseudomonas plecoglossicida(A4)，并与真菌Aspergillus terreus(A)和Phanerochaete Chrysosporium(P)组配构建复配菌GF-Z，其中菌株A3、A4、A对秸秆降解率、滤纸酶活性及木聚糖酶活性具有显著促进作用，菌株P对秸秆降解率、半纤维素降解率、木质素降解率和漆酶活性具有显著提升作用，组成菌株间具有协同效应，其秸秆降解率及木质纤维素降解率较GF-20提高4.85～17.07个百分点，在0.02%～2.5%盐浓度、初始pH 4.0～9.0及13℃～25℃温度范围内，保持较好的稳定性，在模拟环境条件下具有显著的促腐作用。（4）优化筛选技术，采用多层次递进式降解菌系筛选技术，获得复合菌系M44，其玉米秸秆降解率较对照GF-20高3.86个百分点，秸秆组分中半纤维素和木质素降解率分别高出1.57和3.28个百分点，酶活性高出1.44%～17.88%。研究结果为寒旱区实现玉米秸秆大面积原位还田、农业绿色可持续发展提供高效的微生物菌系（种）资源和技术支撑。