| Title | Development of a Novel D‑Lactic Acid Production Platform Based on Lactobacillus saerimneri TBRC 5746 |
|---|---|
| Author | Kitisak Sansatchanon1, Pipat Sudying1,2, Peerada Promdonkoy1, Yutthana Kingcha1, Wonnop Visessanguan1, Sutipa Tanapongpipat1, Weerawat Runguphan1, and Kanokarn Kocharin1* |
| Address | 1National Center for Genetic Engineering and Biotechnology, Klong Luang, Pathum Thani 12120, Thailand, 2Present Address: Chulabhorn Research Institute, Laksi, Bangkok 10210, Thailand |
| Bibliography | Journal of Microbiology, 61(9),853-863, 2023, |
| DOI | 10.1007/s12275-023-00077-x |
| Key Words | D-Lactic acid · Bioplastic · Lactic acid bacteria · CRISPR/dCas9-assisted transcriptional repression |
| Abstract | 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. |