Nature Biotechnology
17, 588 - 592 (1999)
doi:10.1038/9902
Conversion of Lactococcus lactis from homolactic to homoalanine fermentation through metabolic engineeringPascal Hols1, 2, Michiel Kleerebezem1, André N. Schanck3, Thierry Ferain2, Jeroen Hugenholtz1, Jean Delcour2
& Willem M. de Vos11
Microbial Ingredients Section, NIZO Food Research, P.O. Box 20, 6710 BA Ede, The Netherlands. 2
Laboratoire de Génétique Moléculaire, Place Croix du Sud 5, Université catholique de Louvain, 1348 Louvain-La-Neuve, Belgium.
and 3
Laboratoire de Chimie Physique et de Cristallographie, Place Louis Pasteur 1, Université catholique de Louvain, 1348 Louvain-La-Neuve, Belgium.
Correspondence should be addressed to Pascal Hols hols@gene.ucl.ac.bealaninealanine racemasealanine dehydrogenaseLactococcus lactisWe 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.
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