(191ak) Exploiting the L-Lactate Biosynthetic Pathway in Corynebacterium Glutamicum for Heterologous Production of D-Lactate from Biomass-Derived Carbon Substrates

Polylactic acid (PLA), bio-based polymers gained attention as an economically feasible packaging material like fresh fruit container, drinking cups, lamination films, and many more. The skeletal formation of PLA involves the lactic acid as a primary precursor. In the present study, various heterologous strains of Corynebacterium glutamicum (AV41, AV42, AV43, AV44, AV46) were generated to produce D-lactate by exploiting the L-lactate production pathway and followed by ldhA overexpression in the biosynthetic pathway. The heterologous strains with the constitutive promoter were grown in different production media supplemented with different level of different carbon sources. The strain AV46 produced 5887 mg/ L of D-lactate from a minimal media supplemented with glucose as the carbon source. The strains were grown in biomass hydrolysate, and a similar level of D-lactate production 5276 mg/ L was observed. Moreover, upon optimization of pH, the D-lactate production from biomass hydrolysate was enhanced by 1.3 fold, 6945 mg / L at pH 8 in strain AV46. For further utilization of biomass hydrolysate and enhancement of D-lactate production, the strain AV 46 was cultured in different aromatics and found to be growing well without any sugar supplementation. In the preliminary results, we found the strain to be producing D-lactate from aromatics such as benzoic acid, cinnamic acid, vanillic acid, and coumaric acid directly. Additional heterologous proteins are to be overexpressed from xylose and arabinose pathway to increase the ability of these strains to utilize xylose and arabinose as carbon substrate. With the conversion of all major carbon substrates (glucose, xylose, arabinose, and aromatics) in the renewable biomass to D-lactate, we aim to increase the yield, titer, and productivity of D-lactate from biomass hydrolysates.