Succinic acid production from softwood with genome-edited
Corynebacterium glutamicum using the CRISPR-Cpf1 system
Abstract
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 15% 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.