INHIBITION OF PSYCHROTROPHIC ORGANISMS BY PROPIONICIN PLG-1, A BACTERIOCIN PRODUCED BY PROPIONIBACTERIUM-THOENII

Propionibacterium thoenii strain P127, which produces the bacteriocin propionicin PLG-1, was grown in a skim milk medium and produced bacter iocin in that medium. No bacteriocin activity was detected in skim mil k medium in which strain P127-1, a bacteriocin-negative variant of str ain P127, had been grown. Five psychrotrophic spoilage or pathogenic o rganisms (one strain each of Listeria monocytogenes, Pseudomonas fluor escens, Vibrio parahaemolyticus, Yersinia enterocolitica, and one stra in of Corynebacterium sp.) were incubated for 24 h in laboratory mediu m, nonfermented skim milk, and skim milk that had been fermented by st rain P127 or P127-1. Strains were inhibited only in the skim milk ferm ented by strain P127, as evidenced by loss in numbers of viable cells after 24 h at 10-degrees-C and less growth than in other media after 2 4 h at optimal growth temperatures. Growth of selected strains was del ayed or slowed during prolonged incubation (21 d) at 10-degrees-C. Pro pionicin PLG-1 shows promise as a preservative for food products.