Dae-Seok Lee

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Corynebacterium glutamicum is a useful microbe to produce succinic acid, a bio-based platform chemical, under anaerobic condition. The knock-out mutant of lactate dehydrogenase 1 gene (ΔldhA-6) and co-expression of succinic acid transporter (Psod:sucE- ΔldhA) were generated by using CRISPR-Cpf1 genome editing system. HAPC (hydrogen peroxide and acetic acid) pretreatment is a highly efficient method for enzymatic hydrolysis of softwood and the hydrolysate was used for production of succinic acid. In the 15% hydrolysate (Pinus densiflora), the best condition for ΔldhA mutant to produce succinic acid from the hydrolysate was confirmed to ferment 4% hydrolysate, resulted in 14.82 g L-1 succinic acid production for 6 h, which reached to 2.47 g L-1 h-1 productivity. No production of acetic acid and lactic acid was detected during the fermentation. The co-expression transformant, [Psod:sucE- ΔldhA], produced 17.70 g L-1 succinic acid in 6 h, presenting a productivity of 2.95 g L-1 h-1 on the 4% hydrolysate. In the fed-batch system, 39.67 g L-1 succinic acid was produced for 48 h. The yield of succinic acid from reducing sugars in the hydrolysate is approximately 56.71%, while the yield of succinic acid from glucose alone as the main substrate is approximately 84.4%. These results indicated that the production of succinic acid from softwood has potential applications in alternative biochemical processes, and minimizing the loss of sugars during enzymatic hydrolysis and fermentation can lead to more economic benefits in succinic acid production from lignocellulosic biomass.