The Combination of Nisin and ε-Polylysine is Effective to Inhibit the Growth and Production of Biogenic Amines of Enterobacter cloacae

Introduction:  Enterobacter cloacae was frequently isolated from clinical samples and a wide range of foods including meat, milk, and vegetables, and they can also produce cadaverine (CAD) and putrescine (PUT) in foods that cause food spoilage.

Purpose: This study aims to evaluate the combined effects of ε-PL and nisin on the growth of E. cloacae in nutrient broth and chicken meat products. 

Methods: The potential synergistic effects of nisin in combination with ε-PL were evaluated using the fraction inhibitory concentration index (FICI) in nutrient broth. The effect in chicken meat products was then evaluated using the following antimicrobial treatment combinations: N1 (control sample), N2 (ε-PL 0.25 g/kg), N3 (ε-PL 0.125 g/kg,), N4 (nisin 0.5 g/kg), N5 (nisin 0.25 g/kg), N6 (nisin 0.25 g/kg, ε-PL 0.125 g/kg), N7 (nisin 0.125 g/kg, ε-PL 0.125 g/kg), and N8 (nisin 0.125 g/kg, ε-PL 0.06 g/kg). The contents of biogenic amines (BAs) were measured by high-performance liquid chromatography.

Results: The combination of ε-PL and nisin generated a total synergistic effect on the E. cloacae strains as indicated by FICI which were ranged from 0.18 to 0.32. The final OD600 value and the putrescine (PUT) contents in the bacterial culture grown up to 48 h at 37°C treated with nisin–ε-PL, were significantly lower than those of the other groups. The bacterial counts, and the contents of TVB, putrescine (PUT), and cadaverine (CAD) of the N6 and N7 meat groups, which were treated with nisin–ε-PL, were significantly lower than those of the other meat groups.

Significance: The combination of nisin and ε-PL was more effective than application of nisin or ε-PL alone with twofold concentration to inhibit the growth of E. cloacae C1 and production of biogenic amines in chicken meat products.