Efficient production of succinic acid in engineered Escherichia coli strains controlled by anaerobically-induced nirB promoter using sweet potato waste hydrolysate.

Succinic acid has attracted interest worldwide as a precursor of many industrially crucial chemicals. Biosynthesis of succinic acid from biomass is developing as an environmentally friendly strategy now. Conversion of sweet potato waste (SPW) to succinic acid could implement high-value utilization of biomass, cut cost of the fermentation process and reduce the pollution of environment. Engineered Escherichia coli (E. coli) strain HD134 under the control of anaerobically-induced nirB promoter from Salmonella enterica (P_SnirB) could produce about 16.30 g/L succinic acid with a yield of 0.83 g/g after 48 h on glucose. With SPW hydrolysate as the substrate, 18.65 g/L succinic acid with a yield of 0.94 g/g after 48 h fermentation achieved. Compared to SD134 under Trc control induced with Isopropyl β-D-Thiogalactoside (IPTG), this concentration and yield represented an 8.56% and 6.82% increase, respectively. The use of anaerobically-induced P_SnirB not only could attain higher production of succinic acid than IPTG-induced Trc promoter, but omit cost of expensive exogenous inducers. The efficient production of succinic acid from SPW was firstly studied by anaerobically-induced P_SnirB control, which achieved relative lower cost compared to glucose as substrate and IPTG as the inducer. This novel fermentation process conduces to the cosmically industrial succinic acid bioproduction.