title: Homo-D-lactic acid production from mixed sugars using xylose-assimilating operon-integrated Lactobacillus plantarum.
abstract: In order to achieve efficient D-lactic acid fermentation from a mixture of xylose and glucose, the xylose-assimilating xylAB operon from Lactobacillus pentosus (PXylAB) was introduced into an L-lactate dehydrogenase gene (ldhL1)-deficient Lactobacillus plantarum (ΔldhL1-xpk1::tkt-Δxpk2) strain in which the phosphoketolase 1 gene (xpk1) was replaced with the transketolase gene (tkt) from Lactococcus lactis, and the phosphoketolase 2 (xpk2) gene was deleted. Two copies of xylAB introduced into the genome significantly improved the xylose fermentation ability, raising it to the same level as that of ΔldhL1-xpk1::tkt-Δxpk2 harboring a xylAB operon-expressing plasmid. Using the two-copy xylAB integrated strain, successful homo-D-lactic acid production was achieved from a mixture of 25 g/l xylose and 75 g/l glucose without carbon catabolite repression. After 36-h cultivation, 74.2 g/l of lactic acid was produced with a high yield (0.78 g per gram of consumed sugar) and an optical purity of D-lactic acid of 99.5%. Finally, we successfully demonstrated homo-D-lactic acid fermentation from a mixture of three kinds of sugar: glucose, xylose, and arabinose. This is the first report that describes homo-D-lactic acid fermentation from mixed sugars without carbon catabolite repression using the xylose-assimilating pathway integrated into lactic acid bacteria.
authors.affiliation: Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, Nada, Japan.
authors.forename: Shogo
authors.initials: S
authors.lastname: Yoshida
authors.forename: Kenji
authors.initials: K
authors.lastname: Okano
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Tanaka
authors.forename: Chiaki
authors.initials: C
authors.lastname: Ogino
authors.forename: Akihiko
authors.initials: A
authors.lastname: Kondo
mesh_terms: D057465:Catabolite Repression; D017353:Gene Deletion; D018628:Gene Dosage; D005947:Glucose / Q000378:metabolism*; D019344:Lactic Acid / Q000378:metabolism*; D007778:Lactobacillus / Q000235:genetics* / Q000378:metabolism*; D053858:Metabolic Networks and Pathways / Q000235:genetics*; D009876:Operon; D010957:Plasmids; D013997:Time Factors; D014994:Xylose / Q000378:metabolism*
chemical_list: D019344:Lactic Acid; D014994:Xylose; D005947:Glucose