Aims: Activity of the bacteriocin EJ97 produced by Enterococcus faecalis EJ97 against strains of 'Bacillus macroides/B. maroccanus' isolated from spoiled zucchini purée was investigated.
Methods and results: The influence of several factors like bacteriocin concentration, incubation temperature, pH, growth medium and chemical perservatives on bacteriocin activity was investigated. Enterocin EJ97 [2 arbitrary units (AU) per millilitre] had a marked bactericidal effect on strain INRA P53-2 after 4 h of incubation at 37 degrees C, 24 h at 15 degrees C or 48 h at 4 degrees C. Activity was markedly reduced at pH values of 5.0 and 9.0, but was potentiated by sodium nitrite, sodium benzoate, sodium lactate and sodium tripolyphosphate. Inhibition of strain INRA P53-2 in a commercial vegetable purée required a 10-fold higher bacteriocin concentration. Strain EJ97 was able to grow and produce bacteriocin on vegetable purée, but no inhibition of strain INRA P53-2 was detected.
Conclusions: The concentration-dependent bactericidal activity of enterocin EJ97 against strain INRA P53-2 was higher at 37 degrees C and neutral pH, and was potentiated by chemical preservatives. Although enterocin EJ97 was less active in vegetable purée, the concentrations providing bactericidal activity in this food matrix are practical for commercial use.
Significance and impact of the study: Enterocin EJ97 may have a potential for use in the prevention of food spoilage caused by 'B. macroides/B. maroccanus'.