Enhanced production of lactococcin 972 in chemostat cultures.

Lactococcus lactis subsp. lactis IPLA972 is a wild lactococcal strain suitable as a single starter in the manufacture of dairy products. This strain synthesizes lactococcin 972 (Lcn972), a unique bacteriocin that blocks septum formation. In this work, we report on the conditions to optimize biomass and Lcn972 production. In batch cultures, pH 6.8 was found to be optimum for bacteriocin synthesis and both glucose and lactose supported Lcn972 production. The inhibitory activity improved up to eight-fold with increasing carbohydrate concentration. In chemostat cultures, steady states were achieved even at dilution rates higher than mu(max), due to the strong wall growth. Lcn972 behaved as a true primary metabolite, as it was maximally produced when the cells were actively growing. Bacteriocin yields were improved up to ten-fold in chemostat cultures compared with those achieved in batch.