Lactate produced by lactic acid bacteria inhibits their growth. To suppress lactate production, it is necessary to regenerate NAD+ consumed by glycolysis with alternative pathways other than lactate dehydrogenase. In a heterofermentative lactic acid bacterium, Lactobacillus reuteri JCM1112, suppression of lactate production by regenerating NAD+ when producing 1,3-propanediol from glycerol was investigated. The bacterium produced lactate with a yield of 4.7 +/- 0.8 g.g-cell(-1) in a batch culture using glucose as the sole carbon source. When glycerol was added to glucose at a molar ratio (r(Gly/Glc)) of three in the batch culture, the bacterium produced 1,3-propanediol at 1.6 +/- 0.7 g.g-cell(-1).h(-1) and the lactate yield decreased to 3.6 +/- 0.5 g.g-cell(-1). When glycerol was co-fed with glucose exponentially to give a target specific growth rate of 0.1 h(-1) (r(Gly/Glc) = 3), the lactate yield decreased to 1.5 +/- 0.2 g.g-cell(-1). The lactate production when glycerol was added together with glucose was reduced to one-third of that observed in the batch culture using glucose as a carbon source. (C) 2019, The Society for Biotechnology, Japan. All rights reserved.