Suppression of bacteriocin production in mixed-species cultures of lactic acid bacteria

In the present work, the effect of co-culture on bacteriocin production by selected lactic acid bacteria (LAB) was studied. Thus, the co-culture of two bacteriocin-producer strains, Lactobacillus plantarum NC8C and Enterococcus faecium 6T1a, resulted in a significant reduction or even suppression of bacteriocin production by both strains. The phenomenon was not restricted to these two strains since we have further proved that it was more general and also occurred in several other co-cultures with LAB isolated from different food fermentations. This decrease in bacteriocin production was confirmed to be non cell–cell contact-dependent by using a two-compartment system in which the microorganisms were separated by a 0.2-μm-pore-size membrane. In addition, cell-free supernatants from certain co-cultures were able to suppress bacteriocin production in other strain cultures. In light of these findings, we hypothesize that such interactions between microorganisms should be taken into account to improve the development of bacteriocin-producing starter cultures used in food fermentations in order to avoid a negative effect on the quality of the fermented product.