Metabolic engineering of Corynebacterium glutamicum for the efficient production of β-Alanine from glucose

Abstract

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. This study utilized a modified lysine-producing strain as a chassis cell line to further promote β-alanine synthesis through metabolic engineering. In order to reduce the consumption of oxaloacetate, the gene pck was deleted. A promoter mutation library was constructed to screen the original promoter of the stronger promoter replacement gene pyc to enhance the oxaloacetate synthesis pathway and further increase the intracellular supply of oxaloacetate. Next, the gene poxB was deleted, and pyruvate accumulation further promoted β-alanine synthesis. Then, the aspartate kinase-coding gene lysC was weakened by predicting the RBS sequence, thus reducing the synthesis of lysine by-products and improving β-alanine synthesis. Ultimately, the carbon flux in the β-alanine biosynthetic pathways was increased by overexpressing aspartate-α-decarboxylase, aspartate ammonia-lyase, and aspartate aminotransferase using the strong promoter Ptrc. The resulting strain QBA9 was cultured in a 5-L fermenter by fed-batch to produce 70.8 g/L of β-alanine with a productivity of 0.98 g/L/h. These modification strategies demonstrate the potential for efficient β-alanine production by the lysine-producing strain and provide an innovative idea for the developing β-alanine-producing strains.

Funding

Australian Research Council Industrial Transformation Training Centre for Functional Grains,(2021YFC2100900)