Supplementation of medium with diammonium hydrogen phosphate enhanced the d-lactate dehydrogenase levels leading to increased d-lactic acid productivity

The production of d-lactic acid by Lactobacillus lactis RM2-24 was investigated using modified media to increase the efficiency of the fermentation process. The results indicated that the addition of 5 g/l peptone and 1 g/l (NH4)2HPO4 enhanced d-lactic acid production by 32%, as compared to that obtained from non supplemented media, with a productivity of 3.0 g/l/h. Lactate dehydrogenase (LDH) expression profile in these different media was studied which resulted in appearance of additional LDH isoform produced by cells when they were grown in HSYE supplemented with (NH4)2HPO4. The additional LDH appears to be l-LDH contributing to production of l-lactic acid in the fermented broth. This is totally new information in the lactic acid fermentation and could be very useful to industries engaged in d-lactic acid production.