瑞士乳杆菌属于乳杆菌属，广泛应用于食品工业，具有较强的蛋白水解能力，但瑞士乳杆菌增殖过程中蛋白质的水解代谢以及吸收利用机制尚不十分清楚。本研究以瑞士乳杆菌为研究对象，主要开展以下四方面的工作：（1）以αs1-酪蛋白和β-酪蛋白为底物，研究细胞壁锚定蛋白酶的特性，并对蛋白酶基因及表达情况进行分析；（2）对多肽转运系统的特征及选择性进行研究，检测载体相关基因及表达情况；（3）研究细胞内肽酶的类型及水解特性，对肽酶相关基因及表达进行分析；（4）利用蛋白质组学和转录组学技术，对瑞士乳杆菌在蛋白利用过程中的基因表达和蛋白表达情况进行测定，分析参与蛋白质吸收利用过程相关的基因及蛋白种类。通过挖掘四部分数据间的内在联系，系统全面地揭示瑞士乳杆菌氮源吸收代谢及利用机理，旨在为瑞士乳杆菌增殖培养体系设计、发酵剂生产、生物活性肽的制备等提供理论依据。

Lactobacillus helveticus, as one of important lactic acid bacteria (LAB) which have been widely used in food industry, usually hydrolyze milk proteins very well. The proteolytic system of most LAB species including the genus Lactococcus has been well-characterized, but little information is available about the metabolism and utilization of milk-based proteins by L. helveticus strains. The objectives of this study are to: (1) classify the cell envelope proteinase according to gene sequencings and peptides formed after hydrolysis of αs1-casein and β-casein; (2) investigate the specificity and selectivity determinants of peptide transport in L. helveticus, and detect the genes and gene expression of peptide transporters; (3) purify the peptidases from L. helveticus cells cultured in αs1-casein and β-casein media, and characterize molecular cloning and sequence analysis of the peptidase genes; and (4) investigate the gene and protein differential expressions of L. helveticus cultured between the casein medium and the protein-free medium by using proteomics and transcriptomics techniques, and detect the genes and proteins which are related to the process of its nitrogen utilization. Finally, all data out of the mentioned four parts will be processed systematically and to reveal the metabolic and utilization mechanisms of nitrogen sources by the bacteria. This work will provide definitely a theory basis for the designs of L. helveticus multiplication media, as well as the preparations of its starter culture and bioactive peptides.