氮代谢调控子GlnR对希氏乳杆菌耐酸性的调控机制及γ-氨基丁酸合成的影响

乳酸菌在其生态位与工业发酵过程中常遭受多种环境压力胁迫，包括温度，渗透压，醇，酸等。酸胁迫可引起细胞失活及发酵产物产量降低。谷氨酸脱羧酶(GAD)系统对乳酸菌抵抗酸胁迫有重要作用。前期研究发现，氮代谢调控子GlnR直接负调控短乳杆菌的耐酸性，抑制其γ-氨基丁酸(GABA)的合成。而GABA支路作为GABA的分解途径，GlnR对于同时含有GAD系统与GABA支路的乳杆菌的耐酸性的调控机制与作用是不清楚的。本研究以具有GABA支路的希氏乳杆菌为研究对象，通过基因组学、转录分析等，探究GAD系统与GABA支路对菌株耐酸性的影响；采用基因敲除与回补，转录组学，基因蛋白互作等技术，研究GlnR对菌株耐酸性的调控机制，进一步通过全局改造菌株，以期提高突变菌株的耐酸性与GABA合成能力，为深入阐明氮代谢调控子GlnR对乳杆菌的调控机制提供理论支持，同时为希氏乳杆菌的工业化应用提供技术指导。

Lactic acid bacteria are often encounter a variety of environmental stresses in their niche and industrial fermentation process. These stresses include temperature, osmotic stress, alcohol, and acid. Acid stress can cause cell inactivation and product yield loss. The glutamate decarboxylase (GAD) system is vital for lactic acid bacteria. Previous studies have found that the nitrogen metabolism regulator GlnR negatively regulates the acid resistance and inhibits the synthesis of γ-aminobutyric acid (GABA) in Lactobacillus brevis. However, the GABA pathway is the decomposition pathway of GABA, the regulatory mechanism and effect of GlnR on the acid resistance in GABA pathway- containing Lactobacilli is unclear. In this study, GABA-producing L. hilgardii is used as the research object. The effect of GAD system and GABA pathway on the acid resistance is explored through genomics and transcription analysis. The regulatory mechanism of GlnR on the GAD system and GABA pathway is explained in L. hilgardii by gene knockout and complementation, transcriptomic, and gene protein interaction technologies. To improve the acid resistance and GABA synthesis ability of mutant strains, the global modification is implemented. These results reveal GlnR regulatory mechanism in Lactobacilli and provide technical guidance for the industrial application of L. hilgardii.