Modelling of the growth of populations of Listeria monocytogenes and a bacteriocin-producing strain ofLactobacillus in pure and mixed cultures Original Research Article

The cell growth biokinetics of Listeria monocytogenes and a bacteriocin-producing strain ofLactobacillus sake were studied. The organisms were grown both separately and together in a broth system. It was observed that Lact. sake was better suited to growth at low pH than L. monocytogenes. The presence of bacteriocin impacted on L. monocytogenes, by quickly reducing the number of these microbes in mixed populations. A model for the growth ofL. monocytogenes and Lact. sake populations grown separately and in mixed culture is proposed. The model includes a novel approach for better describing the effect of pH change, the ability of Lact. sake to produce bacteriocin and the effect of bacteriocin on L. monocytogenes in the broth culture. Additionally, terms are introduced that describe the competitive effect of one population on the other. The model is fitted to data collected for the growth of each population, either grown alone or together. There were no significant differences between the parameter estimates for each replicate, supporting the hypothesis that the proposed model is a useful representation of the growth and interaction of the two microbial populations.