Effect of Propionibacterium acidipropionici on the growth of Yersinia enterocolitica

The antibacterial effect of Propionibacterium acidipropionici culture on a whey medium was determined in preparations subjected to cell inactivation with UV radiation and chloroform treatment; in concentrated biomass, centrifuged and suspended in sterile water; in a preparation subjected to cell inactivation with chloroform. The test strain was Yersinia enterocolitica 8. The preparations and culture were added, as biopreservatives, to broth media where the test strain was cultured, checking periodically the population development. It was found that a whey culture of P. acidipropionici was characterized by antibacterial activity of 64 AU/ml, but after cell inactivation this activity decreased to 16 and 8 AU/ml, depending on the method employed. The activity of concentrated biomass of live cells was at a level of 128 AU/ml, and after inactivation with chloroform--8 AU/ml. An addition of biopreservatives to the growth medium caused inhibition of test strain proliferation. Its degree depended on the antibacterial activity of the environment and population size. In the environment with activity of 42.7 AU/ml the strain Y. enterocolitica 8 whose population was hundreds of cells per ml died after 8 hours of incubation. A larger population, i.e. 10(5) cfu/ml, survived under these conditions, but did not proliferate during 24 hours of culturing.