Kinetics of growth and lactic acid production from whey permeate by Lactobacillus helveticus

Batch fermentation kinetics of Lactobacillus helveticus were examined in detail. The nature of the culture medium had a significant effect on the product synthesis mechanism. In a glucose synthetic medium, lactic acid produced by the non‐growth‐associated mechanism was less than that by the growth‐associated mechanism. In a lactose synthetic medium, the contribution of both mechanisms was approximately equal at the end of fermentation. In the whey‐yeast extract permeate medium, the contribution by the non‐growth‐associated mechanism was superior to that of the growth‐associated mechanism. Temperature and pH also influenced the relative contribution of the two mechanisms on the total production of lactic acid in whey‐yeast extract permeate medium. Under optimal conditions for temperature and pH, the contribution of non‐growth‐associated product formation was the highest among all temperatures, and the lowest among all pH's. The ATP concentration‐biomass concentration relationship in the batch fermentation process could be roughly approximated by a Luedeking‐Piret‐like equation.