Fig. 7. Over-expression of succinic acid transporter (sucE ) gene and succinic acid production in fed-batch system. (A, B) The gene was inserted onto the genomic DNA of ΔldhA-6 mutant under Psod promoter regulation through the CRISPR/cpf1 gene editing system. (C) The enhancement of succinic acid production was demonstrated in [Psod:sucE- ΔldhA ] transformant (10.00 g CDW) compared toΔldhA mutant (10.94 g CDW) when using 4% hydrolysate. (D) Comparison of the succinic acid production depending on the concentration of hydrolysates was performed with 28~30 g L-1 CDW of [Psod:sucE-ΔldhA ] transformant. (E) A fed-batch system was carried out with an initial concentration of 4% hydrolysate and 30.37 g L-1 CDW of [Psod:sucE-ΔldhA ] transformant. After 24 h of fermentation, 20 mL of 20% pine hydrolysate was added to the reaction solution, resulting in a final concentration of the 4% hydrolysate. Acetic acid was prone to be released during the first 9 h after feeding, while lactic acid was measured at the later stage of the fermentation. (F) The same volume of the 20% hydrolysate was added at 6, 9, and 24 h. P1, Psod promoter; sucE , succinic acid transporter; T1, sacB terminator; P2, Knr promoter; rpsL m, ribosomal S12 protein mutant gene for streptomycin resistant; arrows, feeding.