Lactic acid production by coimmobilized cells of Lactococcus lactis TISTR 1401 and Lactobacillus casei TISTR 1341 using whey as substrate

Abstract

Lactic acid production from whey by batch fermentation of coimmobilized cells of Lactococcus lactis TISTR 1401 and Lactobacillus casei TISTR 1341 was investigated in order to decrease the manufacturing cost of lactic acid. The fermentation was conducted in a two liters fermentor at 37°C and pH 6.5 with an agitation rate of 100 rpm. The maximum lactic acid concentration was obtained with a value of 29.89 g.l-1 and the coimmobilized cells had consistent potential to recycle two rounds of fermentation by producing 17.38 and 12.51 g.l-1 lactic acid in 24 h, for each batch of the first and the second cycle, respectively, while lactic acid produced by free cells in mixed cultures of the two species of the bacteria was 16.63 g.l-1 in 48 h. These results suggested that coimmobilized cell cultures were more effective than free cell mixed cultures in improving lactic acid production.