可溶性糖和以之为主要发酵基质的乳酸菌是影响青贮发酵品质的重要因素。针对苜蓿可溶性糖含量低难青贮的问题，项目组从多种植物的附生乳酸菌中筛选出纤维素分解能力较强的乳酸菌，将之应用于苜蓿青贮，改善了发酵品质。采用N+注入诱变技术成功提高了筛选乳酸菌分解纤维素的性能，选育得到分解纤维素功能乳酸菌（Cly-LAB）10余株。目前尚不清楚选育菌株分解纤维素性能提高的原因，及其改善苜蓿青贮发酵品质的效果和机理。项目组将在基因转录水平研究N+注入诱变对乳酸菌纤维素分解相关酶基因表达的影响；深入细致研究Cly-LAB在苜蓿青贮过程中对结构性糖降解及碳氮源代谢的调控作用，对饲料的酸化能力，与苜蓿附生微生物的互作机制，以及对青贮饲料微生物多样性的影响，探寻Cly-LAB对苜蓿青贮发酵的调控机制和对发酵品质的影响机理。为乳酸菌种质资源创新提供新方向，为创制安全有效、价格低廉的新型苜蓿乳酸菌添加剂奠定研究基础。

Soluble sugar and lactic acid bacteria (LAB) that consume soluble sugar as the main fermentation substrate, are important factors to determine the quality of silage fermentation. To deal with the difficulty in alfalfa ensiling due to its low soluble sugar content, LAB strains that have good capabilities for cellulose degradation were screened out, and applied in alfalfa ensiling, which improved silage fermentation quality. Furthermore, cellulolytic activities of the screened strains were enhanced by N+ ion beam implantation, and more than 10 strains of cellulolytic lactobacillus (Cly-LAB ) were obtained after breeding. The principle of improved cellulolytic capability of Cly-LAB, and their effect and mechanism to improve the fermentation quality of alfalfa silage are not clear. We’ll study the effect of N+ ion beam implantation on the expression of cellulase related genes in LAB on transcriptional scale, and explore Cly-LAB’s regulation of structural sugar degradation, carbon and nitrogen source metabolism, and their effect on microbial diversity of alfalfa silage during ensiling. Their abilities of acidification of feed and interactions with epiphytic microbe will also be discussed. In all, we will give a theoretical explanation on the mechanisms of Cly-LAB’s regulation of alfalfa ensiling fermentation and effect on fermentation quality, which will provide a new direction for the innovation of lactobacillus germplasm resources, and lay a foundation for the creation of safe, effective, and inexpensive alfalfa lactic acid bacteria additives.