Biosynthesis of L-histidine from marine biomass-derived galactans in metabolically engineered Corynebacterium glutamicum

L-Histidine plays significant roles in the food and pharmaceutical industries, and its demand has been steadily increasing recently. As demand for L-histidine continues, the development of eco-friendly processes is required. To pursue this goal, D-galactose, a primary component of red algae, was employed as a carbon source for synthesizing L-histidine. To harness this marine biomass, κ-carrageenan was preferentially hydrolyzed to obtain D-galactose using κ-carrageenase (CgkA) and iduronate-2-sulfatase (IdsA3). Subsequently, L-histidine production was enhanced by modifying precursor pathways in Corynebacterium glutamicum. The resulting strain, TDPH6 exhibited a remarkable 2.15-fold increase in L-histidine production compared to TDP. Furthermore, a galactose utilization system was introduced and named TDPH6G2. During fermentation, this strain efficiently consumed 100 % of the D-galactose and synthesized 0.395 g/L of L-histidine. In conclusion, this study presents a sustainable approach to L-histidine synthesis by introducing a galactose utilization system into C. glutamicum.