Application of enterocin AS-48 as biopreservative in eggs and egg fractions: Synergism through lysozyme

The efficacy of enterocin AS-48 in controlling Bacillus cereus and Staphylococcus aureus in liquid whole egg (LWE), egg white (EW), and egg yolk (EY) at 4 and 28 °C was studied. In LWE, AS-48 yields significant reductions in viable counts of B. cereus with minimum bactericidal concentrations (MBC) of 5 and 0.05 μg/ml respectively at 4 and 28 °C (P < 0.05 and P < 0.01, respectively), notably less than that previously determined in brain heart infusion broth. Results obtained with egg fractions suggest the presence of a compound in EW acting synergistically with AS-48 since, at 4 °C, the MBC for AS-48 was established at 1-2.5 μg/ml. Similar results were obtained for S. aureus in LWE and EW, although the AS-48 MBCs were higher: 5-10 and 1-5 μg/ml respectively at 4 and 28 °C in LWE and 10 μg/ml at 28 °C in EW. In EY, both bacteria showed a much lower susceptibility to AS-48 than in LWE and EW. The combination of lysozyme (8 mg/ml) with AS-48 exerted a synergistic inhibitory effect against B. cereus and S. aureus although this synergy was lower than observed in LWE and EW. This synergy has been also confirmed by electron microscopy observation.