Combinatorial Protein Engineering and Metabolic Engineering for Efficient Synthesis of l-Histidine in Corynebacterium glutamicum .

l-Histidine is an essential proteinogenic amino acid in food with extensive applications in the pharmaceutical field. Herein, we constructed a Corynebacterium glutamicum recombinant strain for efficient biosynthesis of l-histidine. First, to alleviate the l-histidine feedback inhibition, the ATP phosphoribosyltransferase mutant HisG T235P-Y56M was constructed based on molecular docking and high-throughput screening, resulting in the accumulation of 0.83 g/L of l-histidine. Next, we overexpressed rate-limiting enzymes including HisG T235P-Y56M and PRPP synthetase and knocked out the pgi gene in the competing pathway, which increased the l-histidine production to 1.21 g/L. Furthermore, the energy status was optimized by decreasing the reactive oxygen species level and enhancing the supply of adenosine triphosphate, reaching a titer of 3.10 g/L in a shake flask. The final recombinant strain produced 5.07 g/L of l-histidine in a 3 L bioreactor, without the addition of antibiotics and chemical inducers. Overall, this study developed an efficient cell factory for l-histidine biosynthesis by combinatorial protein engineering and metabolic engineering.