The use of enterocin CCM 4231 in soy milk to control the growth of Listeria monocytogenes and Staphylococcus aureus

The inhibitory effect of enterocin CCM 4231 (concentration 3200 AU ml −1 ) was used to control the growth of Listeria monocytogenes Ohio and Staphylococcus aureus in soy milk. The growth and bacteriocin (enterocin) production of producer strain CCM 4231 in soy milk was also checked. Bacteriocin production by CCM 4231 strain in soy milk was first detected after 2 h from the beginning of cultivation (100 AU ml −1 ). The stationary phase for CCM 4231 was reached after 6 h reaching 10·38 cfu ml −1 (log10) with a slight increase up to 24 h (10·43 cfu ml −1 , log10), and the maximum bacteriocin production in soy milk (200 AU ml −1 ) was noted after 8 h of the beginning of cultivation with stability up to 24 h. The addition of enterocin CCM 4231 at 3200 AU ml −1 to a growing indicator strain, L. monocytogenes Ohio, in soy milk resulted in inhibition for 24 h. The high inhibitory effect of enterocin was found after 1 h and 2 h of its addition (in 5 h–6 h of cultivation), the difference between the experimental and the control samples (ES, CS) being 4.96 log cycles at 5 h and 5·15 log cycles at 6 h. Staphylococcus aureus was not fully inhibited, although a difference of 3.55 log cycles was found when ES and CS were compared at the end of cultivation (24 h). The pH was not influenced by enterocin addition. The inhibitory effect of enterocin CCM 4231 against L. monocytogenes Ohio in soy milk was probably bacteriocidal ; while Staph. aureus was influenced bacteriostatically. In general, the observed inhibitory activity confirmed the possibility for further application of bacteriocins in food environments as the protective agents. Of course, legislation problems must be solved.