Suppression of lactate production of Lactobacillus reuteri JCM1112 by co-feeding glycerol with glucose.

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 (rGly/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 (rGly/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.