Electrodialysis for lactate removal in the production of the dairy starter culture Lactococcus lactis NZ133

Abstract

Biomass concentrations of the dairy starter culture Lactococcus lactis NZ133 were increased by the incorporation of an electrodialysis (ED) unit into a batch fermentation grown on 80 g lactose L-1. ED effectively removed the growth inhibitory metabolic end-product lactic acid (as lactate ions) and allowed continued growth beyond that achievable in normal batch fermentation. However, biomass yields per unit lactose were reduced by the probable concomitant loss of other ionic species and nutrients essential for growth. Repeated fed-batch with end-batch ED introduced to minimise this putative loss of nutrients, yielded a final biomass concentration of 12.4 g L-1 on 120 g lactose L-1 medium (biomass yield = 0.05 g g-1), which was appreciably below that observed for standard batch fermentations (biomass yield = 0.12 g g-1). In addition to the reduced yields, the lactic acid production activity of the cells progressively decreased with the increase in number of ED cycles. © 2007 Institute of Food Science and Technology Trust Fund.