Enhancing the antimicrobial activity of d-limonene nanoemulsion with the inclusion of ε-polylysine

- The antimicrobial activity of ε-polylysine, d-limonene and their combination were evaluated against four food-borne pathogens.
- ε-Polylysine and d-limonene displayed strong synergistic and useful additive effects against the tested microorganisms.
- d-limonene nanoemulsion with the inclusion of ε-polylysine, was successfully prepared by high pressure homogenization.
- The formulations showed an enhanced antimicrobial activity as compared with d-limonene nanoemulsion.

The objective of this research was to investigate the synergism between ε-polylysine and d-limonene and develop a novel nanoemulsion system by merging the positive effect of these two antimicrobial agents. Results from the checkerboard method showed that ε-polylysine and d-limonene exhibit strong synergistic and useful additive effects against Escherichia coli, Staphylococcus aureus, Bacillus subtilis and Saccharomyces cerevisiae. In addition, d-limonene nanoemulsion with the inclusion of ε-polylysine was successfully prepared by high pressure homogenizer technology. Its antimicrobial efficiency was compared with pure d-limonene nanoemulsion by measuring the minimal inhibitory concentration, electronic microscope observation and the leakage of the intercellular constituents. The results demonstrated a wide improvement of the antimicrobial activity of d-limonene nanoemulsion following the inclusion of ε-polylysine. Overall, the current study may have a valuable contribution to make in developing a more efficient antimicrobial system in the food industry.