The positive influence of probiotic strains on human health has become increasingly evident and there are numerous scientific studies that highlight how the interaction between different probiotic strains provides even more beneficial action.

Lactobacilli and Bifidobacterium spp. are among the most studied probiotic and/or functional genera and are prominent members of the normal flora of the gastrointestinal tract throughout the host's life.

Today's scientific research in the field of probiotics, prebiotics, and parapostbiotics focuses its attention on the study of the mechanisms that underlie the interaction between these two genera of microorganisms and between the multiple strains belonging to the different species.

This paper shows the first results of a preliminary study on the bioactive action of cell-free supernatants obtained by potential probiotic Lactobacillus plantarum strains towards probiotic strains of Bifidobacteria. In particular, the experimental data obtained were modelled using the Gompertz equation in order to monitor the effectiveness of the bioactive effect of the supernatant on the kinetic parameters of the microbial growth curve. Specifically, the bioactive action was evaluated both in the growth and death phases to also evaluate how the bioactive action acted on the survival of the target strains.

A stimulation/inhibition effect during the bifidobacteria growth and death phases, respectively, were recorded.

In our experimental conditions, a potential “prebiotic” activity and/or an inhibition exerted by the cellular extracts of L. plantarum strains on the growth and death of bifidobacteria was observed; furthermore, a strain dependence on the stimulating strains and a species dependence on the stimulated bacteria was recorded.

This paper could be considered as the first report about the study of the bioactivity of cell-free supernatants from probiotic L. plantarum strains on Bifidobacteria.