POTENTIAL FOR BIOLOGICAL-CONTROL OF AGENTS OF FOODBORNE DISEASE

The competitive interaction of bacteria is well recognized. Natural and controlled food fermentations serve as typical examples of competitive inhibition. Some bacteria produce antagonistic substances (bacteriocins) that are active against other closely related bacteria, in addition to the inhibitory action of pH, organic acids or hydrogen peroxide. Nisin, produced by strains of Lactococcus lactis subsp. lactis, is an excellent example of a relatively broad spectrum bacteriocin that is active against several Gram-positive bacteria, including spore-forming bacteria. Nisin is used as a preservative agent in foods in many countries, and its production by L. lactis in foods is being studied as an approach to safety assurance. Unfortunately nisin is not suitable for use in all food systems because of its limited solubility above pH 5 and its instability in some foods. Production of bacteriocins by lactic acid bacteria from dairy, meat and vegetable foods is the focus of many current research studies. The biological effect, genetic control and chemical structure is being studied to determine the potential for other bacteriocins or bacteriocinogenic strains of lactic acid bacteria as agents for control of foodborne pathogens and spoilage bacteria.