Systems metabolic engineering of Corynebacterium glutamicum for the efficient production of 13-alanine

Abstract

13-Alanine is an important 13-amino acid with a growing demand in a wide range of applications in chemical and food industries. However, current industrial production of 13-alanine relies on chemical synthesis, which usually involves harmful raw materials and harsh production conditions. Thus, there has been increasing demand for more sustainable, yet efficient production process of 13-alanine. In this study, we constructed Corynebacterium glutamicum strains for the highly efficient production of 13-alanine through systems metabolic engineering. First, aspartate 1-decarboxylases (ADCs) from seven different bacteria were screened, and the Bacillus subtilis ADC showing the most efficient 13-alanine biosynthesis was used to construct a 13-alanine-producing base strain. Next, genome-scale metabolic simulations were conducted to optimize multiple metabolic pathways in the base strain, including phosphotransferase system (PTS)-independent glucose uptake system and the biosynthesis of key precursors, including oxaloacetate and L-aspartate. TCA cycle was further engineered for the streamlined supply of key precursors. Finally, a putative 13-alanine exporter was newly identified, and its overexpression further improved the 13-alanine production. Fed-batch fermentation of the final engineered strain BAL10 (pBA2_tr18) produced 166.6 g/L of 13-alanine with the yield and productivity of 0.28 g/g glucose and 1.74 g/L/h, respectively. To our knowledge, this production performance corresponds to the highest titer, yield and productivity reported to date for the microbial fermentation.