FERMENTATION OF CHEESE WHEY IN AN IMMOBILIZED-CELL FLUIDIZED-BED REACTOR

Batch and continuous fermentation of cheese whey to lactic acid were carried out in a fluidized bed reactor by wing Lactobacillus bulgaricus immobilized in 3% (w/v) agarose. Five batch fermentations conducted under un-controlled pH conditions and initial lactose concentrations ranging from 40 to 60g/L gave, an average final lactic acid concentration of 6.9 g/L in a 48 to 50 h period. Continuous fermentation under controlled pH conditions at four different dilution rates ranging from 0.043 to 0.428 h1and a lactose inlet concentration of 43.5 g/L resulted in a lactic acid yield of 0.26 mg/mg lactose consumed. The maximum lactic acid concentration was 10.0 mg/mL at a dilution rate of 0.086 h-1with a substrate utilization of 90.5%. The mathematical model of the system for batch and continuous operations was developed and the model parameters were determined experimentally and by non-linear multiple regression analysis. © 1991, Taylor & Francis Group, LLC. All rights reserved.