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Metabolic engineering of Bacillus subtilis for production of D‐lactic acid
Author(s) -
Awasthi Deepika,
Wang Liang,
Rhee Mun S.,
Wang Qingzhao,
Chauliac Diane,
Ingram Lonnie O.,
Shanmugam Keelnatham T.
Publication year - 2018
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.26472
Subject(s) - metabolic engineering , bacillus subtilis , lactic acid , fermentation , lactate dehydrogenase , biochemistry , lactobacillus , glycerol , biology , strain (injury) , chemistry , trehalose , food science , bacteria , gene , enzyme , genetics , anatomy
Poly lactic acid (PLA) based plastics is renewable, bio‐based, and biodegradable. Although present day PLA is composed of mainly L‐LA, an L‐ and D‐ LA copolymer is expected to improve the quality of PLA and expand its use. To increase the number of thermotolerant microbial biocatalysts that produce D‐LA, a derivative of Bacillus subtilis strain 168 that grows at 50°C was metabolically engineered. Since B. subtilis lacks a gene encoding D‐lactate dehydrogenase ( ldhA ), five heterologous ldhA genes ( B. coagulans ldhA and gldA101 , and ldhA from three Lactobacillus delbrueckii ) were evaluated. Corresponding D‐LDHs were purified and biochemically characterized. Among these, D‐LDH from L. delbrueckii subspecies bulgaricus supported the highest D‐LA titer (about 1M) and productivity (2 g h −1 g cells −1 ) at 37°C ( B. subtilis strain DA12). The D‐LA titer at 48°C was about 0.6 M at a yield of 0.99 (g D‐LA g −1 glucose consumed). Strain DA12 also fermented glucose at 48°C in mineral salts medium to lactate at a yield of 0.89 g g −1 glucose and the D‐lactate titer was 180 ± 4.5 mM. These results demonstrate the potential of B. subtilis as a platform organism for metabolic engineering for production of chemicals at 48°C that could minimize process cost.