The effect of extra addition of lactate on the late stage of fermentation. 1,3-propanediol fed-batch fermentation by KG1 with an initial concentration of glycerol of 40 g/L, in (A), 50 mM lactate were added into the fermentation media in the late stage of fermentation. And in (B), there is no addition of lactate. Open squares, biomass; closed triangles, lactate; closed inverted triangles, 3-hydroxypropionaldehyde (3-HPA). The datapoints represent the mean values and standard deviations of three parallel experiments.