Influence of Yeast Extract concentration on Lactic Acid Production fromWhey in Batch Reactor by Lactobacillius bulgaricus

The disposal of whey, the liquid remaining after the separation of milk fat and casein from whole milk is a major problem for dairy industry which demands simple and economical solutions.Ultra filter whey with different nutritional and process parameters was used as a substrate for lactic acid production by different strains of homofermentative lactobacilli.In this research different concentration of yeast extract (0,5,10,15 g/l) was used in media for lactic acid production. Batch process with retention time of 72 hours for lactic acid production was obtained. For batch process 10 g/l yeast extract was found to be optimal. The initial lactose concentration in whey was 50 g/l and the final lactose concentration was 4 g/l. At this amount of yeast extract the lactose consumption and conversion to lactic acid and biomass was 92 percent ، yield was 42 percent and productivity was 0.6 g.l-1.h-1. When the yeast extract concentration increases to 15 g/l inhibition effect occured.

کلیدواژه ها:

Whey ، Batch process ، Lactobacillius bulgaricus ، Lactic acid ، Yeast extract