title: Conversion of Lactococcus lactis from homolactic to homoalanine fermentation through metabolic engineering.
abstract: We report the engineering of Lactococcus lactis to produce the amino acid L-alanine. The primary end product of sugar metabolism in wild-type L. lactis is lactate (homolactic fermentation). The terminal enzymatic reaction (pyruvate + NADH-->L-lactate + NAD+) is performed by L-lactate dehydrogenase (L-LDH). We rerouted the carbon flux toward alanine by expressing the Bacillus sphaericus alanine dehydrogenase (L-AlaDH; pyruvate + NADH + NH4+ -->L-alanine + NAD+ + H2O). Expression of L-AlaDH in an L-LDH-deficient strain permitted production of alanine as the sole end product (homoalanine fermentation). Finally, stereospecific production (>99%) of L-alanine was achieved by disrupting the gene encoding alanine racemase, opening the door to the industrial production of this stereoisomer in food products or bioreactors.
authors.affiliation: Microbial Ingredients Section, NIZO Food Research, Ede, The Netherlands. hols@gene.ucl.ac.be
authors.forename: P
authors.initials: P
authors.lastname: Hols
authors.forename: M
authors.initials: M
authors.lastname: Kleerebezem
authors.forename: A N
authors.initials: AN
authors.lastname: Schanck
authors.forename: T
authors.initials: T
authors.lastname: Ferain
authors.forename: J
authors.initials: J
authors.lastname: Hugenholtz
authors.forename: J
authors.initials: J
authors.lastname: Delcour
authors.forename: W M
authors.initials: WM
authors.lastname: de Vos
mesh_terms: D000409:Alanine / Q000378:metabolism*; D050788:Alanine Dehydrogenase; D000411:Alanine Racemase / Q000235:genetics; D000594:Amino Acid Oxidoreductases / Q000235:genetics; D001407:Bacillus / Q000201:enzymology; D001483:Base Sequence; D002384:Catalysis; D017931:DNA Primers; D005285:Fermentation; D007536:Isomerism; D007773:Lactates / Q000378:metabolism*; D013294:Lactococcus lactis / Q000378:metabolism*; D008969:Molecular Sequence Data
chemical_list: D017931:DNA Primers; D007773:Lactates; D000594:Amino Acid Oxidoreductases; D050788:Alanine Dehydrogenase; D000411:Alanine Racemase; D000409:Alanine