Production of Lactic Acid from Whey Using Immobilized ‎Mixed Culture of Streptococcus thermophilus and Lactobacillus ‎bulgaricus

Sahar Adnan Sheet(1) and Waleed Ahmed Mahmood*(1)

(1). Faculty of Agriculture and Forestry, University of Mosul, Iraq.

 (*Corresponding author: Dr. Waleed Ahmed Mahmood, E-Mail:

Received: 12/01/2020                               Accepted: 12/04/2020


This study was carried out at Faculty of Agriculture and Forestry, University of Mosul during 2018 and 2019 seasons. Lactic acid was produced from cheese whey of buffalo’s milk by a mixed culture of Streptococcus thermophilus and Lactobacillus bulgaricus immobilized in calcium alginate gel by using batch fermentation. Some factors affecting immobilization efficiency and lactic acid productivity were studied. Results indicated that the concentration of 2% sodium alginate in the cell suspension resulted in maximum immobilization efficiency and acid production with significant differences from the other used concentrations (1 and 2%). Maximum acid productivity and immobilization efficiency were obtained upon using calcium chloride with concentrations of 4 and 5%, respectively. Beads diameter of 3 mm resulted in the highest immobilization efficiency and acid productivity. 45-60 minutes of beads solidification time were found suitable to obtain high immobilization efficiency and lactic acid productivity. Results showed that low inoculum concentration (5×107 cell/ml) was preferred for obtaining the highest immobilization efficiency, which was significantly dropped upon increasing of inoculum concentration. Maximum lactic acid production was obtained by using inoculum concentration of 20×107 cell/ml with non-significant differences over the range of 10-25×107 cell/ml. Immobilized cells were reused for four runs and a significant loss in activity was observed during the successive runs.

Key words: Lactic acid,Streptococcus thermophilus, Lactobacillus bulgaricus, whey, Immobilized cells.

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