PROPIONIBACTERIUM FREUDENREICHII STRAINS AS ANTIBACTERIAL AGENTS AT NEUTRAL PH AND THEIR PRODUCTION ON FOOD-GRADE MEDIA FERMENTED BY SOME LACTOBACILLI

摘要

Propionibacteria are food-grade microorganisms that can suppress undesirable microbes in food. Profitability of their application depends on their effectiveness against food-spoiling bacteria and on the accessibility of the protective product. In thisstudy, the ability of Propionibacterium freudenreichii Pr4 to retard the growth of Bacillus subtilis, Bacillus cereus, Pseudomonas putida and Escherichia coli at neutral pH was proven. The efficiency of P. freudenreichii culture broth against all thesebacteria, except E. coli, was similar to that of the chemical propionate, taken in the same amounts. Consequent cultivation with certain lactic acid bacteria was found to be a convenient way to achieve active growth of P. freudenreichii on food-grade media. The pregrowth of Lactobacillus acidophilus 146 in skim milk and milk whey stimulated considerably the growth of P. freudenreichii Pr2 and the production of propionate. The final amount of P. freudenreichii Pr2 and L. acidophilus 146 viable cells in this case was 1.5 and 2 times more than when the bacteria grew separately. Other three Lactobacillus species tested did not provide stimulating effects. Sequential fermentation with Lactobacillus delbrueckii B-3887 allowed to provide the growth of P. freudenreichii Pr4 in wheat flour medium and to get preparation that contains enough propionate for antirope bread protection.