Influence of polysaccharides on oxygen dependent lactate utilization by an amylolytic Lactobacillus plantarum strain

Oxygen-dependent conversion of lactate to acetate by the amylolytic strain Lactobacillus plantarum A6 was studied using MRS-grown cells, transferred to a basic medium with lactate. In the presence of oxygen, lactate was stoechiometricaly converted to acetate. When glucose, maltose or cellobiose was added to the basic medium, no utilisation of lactate was observed. However, when starch or glycogen was added, the conversion of lactate to acetate happened. To verify the possible link of this effect with sugar consumption rate, a glucose-fed batch culture was conducted with a lactic acid consuming culture grown on the basic medium with lactate. Even when glucose was fed at the same low rate as the consumption rate observed for polysaccharides, lactic acid was no more consumed. For the amylolytic strain L. plantarum A6, the transport and use of oligosaccharides resulting from polysaccharides hydrolysis might affect differently the glycolytic flux, with the putative consequence to suppress the metabolic control of glycolysis by glucose. This fact could play an important role in the fermentation of amylaceous foods.