Les bactéries lactiques sont productrices d'acide lactique; plus la densité bactérienne est importante plus le métabolisme et la biosynthèse des métabolites (acide lactique) est importante.

3/5/20

Dear Ivan,

Lactic acid bacteria (LAB), like other bacteria, derive energy from the Embden-Myerhoff (glycolytic) pathway. The starting material is glucose (or similar sugar); the end product is pyruvic acid. In carrying out glycolysis, the cells consume NAD, converting it into NADH. Once all the NAD is converted to NADH, glycolysis stops. To keep the pathway operating so the cells can grow, the cells need to re-generate NAD from NADH (See attached.).They do this using the enzyme lactic acid dehydrogenase (LDH). This converts pyruvic acid into lactic acid, which is excreted by the cells. LDH requires NADH as a cofactor to reduce pyruvic to lactic. During the reaction, the cells regenerate NAD to allow glycolysis to continue. So, conversion of pyruvic to lactic is essential for continuation of the cells' metabolism and energy production.

I have grown LAB a number of times. The presence of lactic acid in the fermentation medium doesn't seem to hurt the cells. Lactic acid is produced commercially this way. See the attached growth profile which we prepared a few years ago.

I hope this information helps you.

Bill Colonna

Center for Crops Utilization Research, Iowa State University, Ames, IA , USA

[email protected]

@W.J. Colonna

Thank you for your answer!