[Metabolic engineering of Lactobacillus plantarum for direct L-lactic acid production from raw corn starch]

5 years ago

[Metabolic engineering of Lactobacillus plantarum for direct L-lactic acid production from raw corn starch]

Tsutomu Tanaka, Shinji Hama, Akihiko Kondo, Kohsuke Honda, Gentaro Uematsu, Hideo Noda, Kenji Okano

Fermentative production of optically pure lactic acid (LA) has attracted great interest because of the increased demand for plant-based plastics. For cost-effective LA production, an engineered Lactobacillus plantarum NCIMB 8826 strain, which enables the production of optically pure L-LA from raw starch, was constructed. The wild-type strain produces a racemic mixture of D- and L-LA from pyruvate by the action of the respective lactate dehydrogenases (LDHs). Therefore, the gene encoding D-LDH (ldhD) was deleted. Although no decrease in D-LA formation was observed in the ΔldhD mutant, additional disruption of the operon encoding lactate racemase (larA-E), which catalyzes the interconversion between D- and L-LA, completely abolished D-LA production. From 100 g/L glucose, the ΔldhD ΔlarA-E mutant produced 87.0 g/L of L-LA with an optical purity of 99.4%. Subsequently, a plasmid was introduced into the ΔldhD ΔlarA-E mutant for the secretion of α-amylase from Streptococcus bovis 148. The resulting strain could produce 50.3 g/L of L-LA from raw corn starch with a yield of 0.91 (g per g of consumed sugar) and an optical purity of 98.6%. The engineered L. plantarum strain would be useful in the production of L-LA from starchy materials.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/biot.201700517