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Metabolic Engineering of Lactobacillus plantarum for Direct l ‐Lactic Acid Production From Raw Corn Starch
Author(s) -
Okano Kenji,
Uematsu Gentaro,
Hama Shinji,
Tanaka Tsutomu,
Noda Hideo,
Kondo Akihiko,
Honda Kohsuke
Publication year - 2018
Publication title -
biotechnology journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.144
H-Index - 84
eISSN - 1860-7314
pISSN - 1860-6768
DOI - 10.1002/biot.201700517
Subject(s) - lactobacillus plantarum , lactic acid , starch , food science , chemistry , mutant , strain (injury) , bacteria , corn steep liquor , biochemistry , metabolic engineering , fermentation , biology , enzyme , gene , genetics , anatomy
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, is 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 ) is deleted. Although no decrease in d ‐LA formation is observed in the Δ ldhD 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 −1 glucose, the Δ ldhD Δ larA‐E mutant produces 87.0 g L −1 of l ‐LA with an optical purity of 99.4%. Subsequently, a plasmid is introduced into the Δ ldhD Δ larA‐E mutant for the secretion of α‐amylase from Streptococcus bovis 148. The resulting strain could produce 50.3 g L −1 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.