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

Corynebacterium glutamicum is a useful microbe that can be used for producing succinic acid under anaerobic conditions. In this study, we generated a knock-out mutant of the lactate dehydrogenase 1 gene (ΔldhA-6) and co-expressed the succinic acid transporter (Psod:SucE- ΔldhA) using the CRISPR-Cpf1 genome editing system. The highly efficient HPAC (hydrogen peroxide and acetic acid) pretreatment method was employed for the enzymatic hydrolysis of softwood (Pinus densiflora) and subsequently utilized for production of succinic acid. Upon evaluating a 1%-5% hydrolysate concentration range, optimal succinic acid production with the ΔldhA mutant was achieved at a 4% hydrolysate concentration. This resulted in 14.82 g L-1 succinic acid production over 6 h. 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. In the fed-batch system, 39.67 g L-1 succinic acid was produced over 48 h. During the fermentation, the strain consumed 100% and 73% of glucose and xylose, respectively. The yield of succinic acid from the sugars consumed was approximately 0.77 g succinic acid/g sugars. These results indicate that the production of succinic acid from softwood holds potential applications in alternative biochemical processes.

A High-Yield Process for Production of Biosugars and Hesperidin from Mandarin Peel Wastes.

In this research, novel biorefinery processes for obtaining value-added chemicals such as biosugar and hesperidin from mandarin peel waste (MPW) are described. Herein, three different treatment methods were comparatively evaluated to obtain high yields of biosugar and hesperidin from MPW. Each method was determined by changes in the order of three processing steps, i.e., oil removal, hesperidin extraction, and enzymatic hydrolysis. The order of the three steps was found to have a significant influence on the production yields. Biosugar and hesperidin production yields were highest with method II, where the processing steps were performed in the following order: oil removal, enzymatic hydrolysis, and hesperidin extraction. The maximum yields obtained with method II were 34.46 g of biosugar and 6.48 g of hesperidin per initial 100 g of dry MPW. Therefore, the methods shown herein are useful for the production of hesperidin and biosugar from MPW. Furthermore, the utilization of MPWs as sources of valuable materials may be of considerable economic benefits and has become increasingly attractive.