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Theppanya Charoenrat,Kanyalak Sangprapai,Peerada Promdonkoy,Kanokarn Kocharin,Sutipa Tanapongpipat,Niran Roongsawang 한국생물공학회 2015 Biotechnology and Bioprocess Engineering Vol.20 No.2
Control of the methanol supply during the production stage is a crucial parameter for maintaining cell growth and enhancing recombinant protein production by Pichia pastoris. In this study, optimization of the initial specific methanol supply rate was explored for high cell density fed-batch cultivation of recombinant fungal β- glucosidase in a slow methanol utilization strain (MutS), P. pastoris KM71. By varying the methanol feed rates for initiating the induction at a cell concentration of 60 g/L, the optimum initial specific methanol supply rate was determined to be 30.34 ± 0.34 mg/g·h. A methanol feed rate was proposed according to this optimum parameter and applied for the production of recombinant β-glucosidase at the higher cell concentrations of 80 and 100 g/L. The highest recombinant β-glucosidase activity obtained was 2851.7 ± 14.6 U/mL, which was four times higher than that obtained with the reference condition (40 g/L initial cell concentration). The success of this approach suggests that the strategy of optimizing the initial specific methanol supply rate could be adopted and applied for the production of other recombinant proteins in P. pastoris employing a methanol inducible system.
Development of a Novel D-Lactic Acid Production Platform Based on Lactobacillus saerimneri TBRC 5746
Sansatchanon Kitisak,Sudying Pipat,Promdonkoy Peerada,Kingcha Yutthana,Visessanguan Wonnop,Tanapongpipat Sutipa,Runguphan Weerawat,Kocharin Kanokarn 한국미생물학회 2023 The journal of microbiology Vol.61 No.9
D-Lactic acid is a chiral, three-carbon organic acid, that bolsters the thermostability of polylactic acid. In this study, we developed a microbial production platform for the high-titer production of D-lactic acid. We screened 600 isolates of lactic acid bacteria (LAB) and identified twelve strains that exclusively produced D-lactic acid in high titers. Of these strains, Lactobacillus saerimneri TBRC 5746 was selected for further development because of its homofermentative metabolism. We investigated the effects of high temperature and the use of cheap, renewable carbon sources on lactic acid production and observed a titer of 99.4 g/L and a yield of 0.90 g/g glucose (90% of the theoretical yield). However, we also observed L-lactic acid production, which reduced the product’s optical purity. We then used CRISPR/dCas9-assisted transcriptional repression to repress the two Lldh genes in the genome of L. saerimneri TBRC 5746, resulting in a 38% increase in D-lactic acid production and an improvement in optical purity. This is the first demonstration of CRISPR/dCas9-assisted transcriptional repression in this microbial host and represents progress toward efficient microbial production of D-lactic acid.