Ecofriendly Synthesis of L-Carnosine in Metabolically Engineered Corynebacterium glutamicum by Reinforcing Precursor Accumulation

Abstract

Biobased processes to minimize environmental pollutants have attracted much attention. L-Carnosine has been produced by chemical synthesis, and as an alternative to this method, we newly developed engineered Corynebacterium glutamicum synthesizing L-carnosine. To develop the strain, the pentose phosphate pathway (PPP) was enhanced by attenuating flux to nonoxidative PPP. Enhanced PPP strengthened the histidine pathway and produced 5.0 g/L L-histidine and 3.9 mg/L L-carnosine. Then, the histidine synthetic pathway was reinforced by overexpressing HisG and Rel. This pathway reduced feedback inhibition by L-histidine and strengthened the flux of the histidine pathway; thus, it produced 552.20 mg/g (DCW) L-histidine. As a result, enhancement of the PPP accumulates more L-histidine than the histidine pathway; thus, the PPP was further enhanced by pgi gene alteration. For sufficient beta-alanine products, PanD was overexpressed and produced 99.17 mg/L L-carnosine. The final strain, Car15, which consolidated all three pathways, produced 323.26 mg/L L-carnosine via fed-batch fermentation. Finally, we confirmed the antioxidant and antiglycation effects of biologically synthesized L-carnosine, and the biologically synthesized L-carnosine showed inhibitory activity similar to that of commercial L-carnosine. Consequently, this study suggested a new biosynthetic process for L-carnosine and showed potential as a treatment for metabolic disorders through the assessment of its functions.