构建pyc启动子突变文库改造谷氨酸棒杆菌高效生产β-丙氨酸

β-Alanine is the only naturally occurring β-type amino acid, with various applications in the pharmaceutical, food, and chemical industries. Given the growing market demand, the study of β-alanine production is important. In this study, the modified lysine-producing strain XQ-5.5 was used as the starting strain to further promote the synthesis of β-alanine through the construction of chassis cells and pyc promoter mutation library. To increase the intracellular supply of oxaloacetate and ensure its conversion to aspartate (a direct precursor of β-alanine), the phosphoenolpyruvate carboxylase coding gene pck was deleted. In order to ensure sufficient pyruvate to maintain tricarboxylic acid cycle and oxalacetate synthesis, the pyruvate oxidase coding gene poxB was also deleted. Next, an attempt was made to fine-regulate the gene pyc to further ensure sufficient oxalacetate content for β-alanine synthesis. The carbon flux from pyruvate to oxalacetate was increased through the construction and screening of pyc promoter random mutation library. Finally, the strain XQ-5.7 was cultured in a 5L fermenter with batch feeding, and the yield of β-alanine was 62.8 g L-1.