LACTIC-ACID PRODUCTION FROM DEPROTEINIZED WHEY BY MIXED CULTURES OF FREE AND COIMMOBILIZED LACTOBACILLUS-CASEI AND LACTOCOCCUS-LACTIS CELLSUSING FEDBATCH CULTURE

The production of lactic acid from deproteinized whey by mixed culture s of free and coimmobilized Lactobacillus casei and Lactococcus lactis cells in batch and fedbatch culture was investigated. Fedbatch cultur e proved to be a better fermentation system for the production of lact ic acid than batch culture. The maximum lactic acid concentration (46 g l(-1)) in fedbatch culture was obtained with both free cells mixture and coimmobilized cells at a substrate concentration of 100 g l(-1) a nd a feeding rate of 250 mi h(-1). In repeated fedbatch culture, coimm obilized L. casei and L. lactis cells gave a higher overall lactic aci d concentration compared with the free cells mixture. The coimmobilize d L. casei and L. lactis cells in Ca-alginate beads retained their abi lity to produce lactic acid for 20 days. (C) 1998 Elsevier Science Inc .