Bioconversion of Whey to Lactic Acid Using Lactic Acid Bacteria (LAB)
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Lactic acid is a natural organic acid, which is an industrially important product. It is used in pharmaceuticals, cosmetics, and chemical, textile and food industries. Novel applications in synthesis of biodegradable plastics have increased the demand for lactic acid. Microbial fermentations are preferred over chemical synthesis of lactic acid due to many factors. The whey is highly pollutant to environment and disposal of whey may causes number of problems. But whey is potential source of lactose and other beneficial minerals. This characteristic makes the whey to be a main substrate for production of lactic acid from whey and other biological products. In this project cheese whey was used as a raw material for microbial lactic acid production with Lactic Acid Bacteria (LAB). In the first part of this study LAB was isolated from dairy by- product whey. After that the growth rate of the isolated LAB was studied. Finally the effect of whey concentration on lactic acid production was investigated using batch fermentation which is carried out in 500 ml Erlenmeyer flask and the temperature was maintained at 37oC throughout the fermentation. As a result of intensive experiments for LAB isolation, nearly pure LAB was obtained. While in the second part the growth rate constant was 0.64 h-1 and the generation time is about 1.09 h. In the third part of this study, first the whey was concentrated by vacuum evaporation to be used for lactic acid production. The total solid (TS) obtained after evaporation process was about 117 g/l. Two different initial whey concentrations were used 10 g/l and 20 g/l. It was found that the lactic acid concentration is about 0.342 (w/w)% when initial whey concentration 10 g/l is used, while about 0.401 (w/w)% of lactic acid was formed in case of 20 g/l after 5 hours of cultivation. The results obtained in this work confirmed that it is possible to increase the value of residues from the dairy industry for the production of value-added products such as lactic acid, which has important industrial applications. This could reduce the cost of the culture media used for lactic acid production when scaling up the process.