Production of Succinic Acid by Metabolically Engineered Actinobacillus succinogenes from Lignocellulosic Hydrolysate Derived from Barley Straw.

Succinic acid is an industrially important component that plays a key role in food additives, dietary supplements, and precursors for biodegradable polymers. Due to environmental and economic issues, succinic acid production has become increasingly attractive. This work aimed to improve succinic acid production from lignocellulosic biomass in Actinobacillus succinogenes through genetic modifications and fermentation strategies. Firstly, the effects on succinic acid production by overexpressing genes encoding phosphoenol carboxylase, malate dehydrogenase, and fumarase were evaluated in batch fermentations of engineered A. succinogenes strains. The engineered A. succinogenes expressing PCK, MDH, and FUM (AS-PMF) showed a 1.3-fold increase in succinic acid production compared to the wild-type strain. Subsequently, the fed-batch fermentation with MgCO₃ was carried out using AS-PMF, which led to producing 50 g/l of succinic acid with 0.79 g/g of yield. Finally, 22.2 g/l of succinic acid with 0.64 g/g of yield was achieved in batch fermentation from lignocellulosic hydrolysate of barley straw. These results support that sustainable succinic acid from agricultural wastes might be a promising strategy for industrial applications.