Modeling microbial interactions to optimize food preservation.

Many microbial processes deal with mixed populations of microorganisms. For instance, many traditional fermentation processes, such as the preparation of yogurt, cheese and tofu, make use of cultures that consist of different species of microbes. Also, various microorganism species are important when food safety and spoilage are involved. The various microorganisms may interact with each other, leading to a different behavior by the individual species, unlike when they are pure cultures.

In food preservation, these interactions are exploited to prevent pathogenic and spoilage organisms from growing. Acid- or bacteriocin-producing organisms are added to products to inhibit microbial growth. Scientists at Wageningen Agricultural University, (PO Box 8129, 6700 EV Wageningen, The Netherlands) are developing a general technique for quantifying the effects of microbial interactions. They are combining transport phenomena with the biological activity of interacting microorganisms.

Researchers have created a three-dimensional grid of microenvironments, which they assumed to be homogeneous. The microbial conversion rates and transport rates were calculated on the basis of the concentrations of compounds and cells in each microenvironment. With these rates the concentrations of various compounds and microbes of interest have been evaluated by the investigators.

To support the theoretical work, the interaction between L. curvatus and E. cloacae was studied as a model system. The behavior of both microorganisms was modeled individually in shake flasks. After researchers developed the models, they predicted the behavior in mixed cultures.

Further information. D. Martens; phone: [phone]; URL: http://www.wau.nl.