Amelioration of lactic acid production from cheese whey using micro-aeration

Abstract

Pilot-scale continuous mix bioreactors were used to study the effect of micro-aeration (0.00–0.15 vvm) on the cell growth of Lactobacillus helveticus, lactose utilization and lactic acid yield under batch fermentation of cheese whey having initial lactose concentrations ranging from 50 to 150 g/l. The experiments were conducted under controlled pH (5.5) and temperature (42°C) conditions. The results indicated that micro-aeration significantly improved the maximum cell number and the specific growth rate. It also enhanced the lactose utilization rate and lactic acid yield. The optimum micro-aeration level for the lactose fermentation process was found to be 0.10 vvm. Further increases in the micro-aeration rate slightly decreased both the cell number and the lactic acid yield due oxygen toxicity to the bacterial cells. The maximum lactic acid yield was obtained with the micro-aeration rate of 0.10 vvm and the 75 g/l initial lactose concentration.