雪莲菌发酵乳中S层蛋白介导的高加索乳杆菌与酿酒酵母菌识别共生机制

雪莲菌发酵乳是我国牧区传统饮品，具有良好的风味和益生功能，其工业化生产将有助于改善国内市场发酵乳品种单一，发酵剂依赖进口的现状。揭示乳酸菌与酵母菌的共生机制是构建雪莲菌发酵剂、实现工业化的必要前提。前期发现S层蛋白（SLP）是介导乳酸菌与酵母菌识别的关键物质，但具体作用机制尚不明晰。本项目以雪莲菌为研究对象，以SLP为切入点，对分离得到的产SLP高加索乳杆菌进行全基因组测序，注释解析SLP编码基因并预测功能结构域；利用分子模拟及重组蛋白验证相结合的方法，明确SLP的识别位点，揭示SLP识别酵母细胞的分子对接机制；在此基础上，针对人工构建发酵剂菌相聚集后无法稳定增长的问题，利用免疫原理、点突变技术及多组学技术进行菌相间的共生应答分析，发现应答通路及应答因子，阐明乳酸菌与酵母菌的共生机制。项目成果将为构建雪莲菌发酵剂并形成自主知识产权提供理论依据，为实现雪莲菌发酵乳的可控发酵和工业化奠定基础。

Tibet kefir is a kind of traditional yoghurt in pastoral area of China, which is of delightful flavor and various beneficial activities. Industrialization of Tibet kefir will be very helpful in the diversified development of fermented milk products in domestic market. Moreover, current situation of imported dairy starter will be improved. In order to make it industrialized, it is indispensable to uncover the mechanism of identification and symbiosis between lactic acid bacteria and yeast. Previous studies have proved that Surface layer proteins (SLP) are key factors for identification and aggregation of lactic acid bacteria and yeast, but the mechanism remains unclear. In this project, whole genome sequencing will be applied to Lactobacillus kefiri, which has been isolated form Tibet kefir, to analyze the encoding genes and predict the functional domains of SLP. Molecular modeling combined with protein recombination will be used to find out the identification site and the mechanism of molecular docking between SLP and yeast cell. On this basis, immunity principles, point mutation and multi-omics will be used for symbiotic response analysis to find out response pathways and factors. Then, the symbiotic mechanism will be clarified. The results of this project will provide a theoretical basis for the construction of Tibet kefir starter with independent intellectual property rights, and lay the foundation for controllable fermentation and industrialization of Tibet kefir.