Effect of Various Parameters of Carbon and Nitrogen Sources and Environmental Conditions on the Growth of Lactobacillus Casei in the Production of Lactic Acid
Lactic acid is widely used in food and pharmaceutical industries and is produced by two biological (fermentative processes) and synthetic methods. Due to the production capacity of isomer L(+), the highest global production of lactic acid is done by fermentation. Lactobacillus casei strain was used in this study that is the homofermentative bacteria producing L(+)-lactic acid. Two nitrogen sources of yeast extract and corn steep liquor and two sugar sources of sucrose and molasses at temperatures of 37 Cº, 40 Cº and 42 Cº as well as two pHs 5 and 7 were used in the study. The results showed that higher lactic acid is produced by increasing the amount of yeast extract compared to the use of corn steep liquor. Moreover, Lactobacillus casei using sucrose produced more lactic acid than the molasses. The optimal temperature for lactic acid produced by the bacterium was 37 Cº in these experiments. In addition, it was found that Lactobacillus casei could produce more lactic acid at pH = 5 than at pH = 7, and the production of the acid reached the maximum value at pH = 5. In optimum conditions, 60/90g/L Lactic acid was obtained after 24 hours incubation of samples (pH = 5 and 37 Cº).
