酸奶发酵剂菌株半乳糖代谢通路的重塑及其调控机理的研究

酸奶是以鲜牛奶为原料，经乳酸菌发酵得到的一种酸性适中的奶制品。然而在市售酸奶中，除已有的天然糖外，还添加了一定量的蔗糖，严重损害了酸奶作为健康食品的形象。随着人们健康意识的提高，积极研制并开发“低糖、高甜度”乳制品已成为食品科学与健康领域的研究热点。本课题以具有良好发酵特性的酸奶发酵剂及其代谢半乳糖的诱变株为研究对象，采用PacBio SMRT测序平台进行基因组测序，找出和半乳糖代谢密切相关的功能基因。在此基础上，利用转录组学和代谢组学方法对酸奶发酵剂和半乳糖诱变株在发酵过程中的代谢多样性进行深入系统的研究，针对部分差异表达基因，使用d-PCR绝对定量技术进行功能验证，以期揭示酸奶发酵剂和半乳糖诱变株的表型差异产生的分子机制。该项目的实施和完成，为乳酸菌资源和新型乳制品的开发提供必要的科学理论依据。

Yogurt is a kind of moderately sour milk product, which is made from fresh milk and is fermented by lactic acid bacteria. However, in addition to natural sugar, a certain amount of sucrose is added in commercial yogurt products, which seriously damage the image of yogurt as a healthy food. With the improvement of health awareness of the public, it has become a hot topic in food and health sciences to develop dairy products of low sugar and high sweetness. In this study, some yogurt starter strains will be selected as research objects; they have good fermentation characteristics and are mutagenic to enable their capacity in galactose metabolism. Their genomes will be sequenced using the PacBio SMRT sequencing platform to identify functional genes closely related to galactose metabolism. The fermentative and metabolic activities of these strains will be systematically studied together with transcriptomics and metabolomics. To reveal the molecular mechanism of phenotypic differences of yogurt starter and galactose mutants, functional verification will be performed using an absolute gene quantification approach, d-PCR, to quantify selected differentially expressed genes. The implementation and completion of the current project will provide scientific and theoretical basis for utilizing resources of lactic acid bacteria and developing innovative dairy products.