The influence of glycerol (100 mM) on the growth kinetic and the end-products formation by Lactobacillus reuteri growing on maltose (29 mM) was examined in aerobiosis and anaerobiosis. The presence of glycerol in aerated cultures changed the maltose consumption but not the growth rate nor the fermentation balance. In a nitrogen atmosphere, L. reuteri was not able to grow on maltose alone. In the presence of both, maltose and glycerol, L. reuteri changed its fermentation pattern, producing 58 mM 1, 3-propanediol as the major end product.