Antimicrobial Oil-in-Water Nanoemulsions: Synergistic Effect of Nisin and Carvacrol against Bacillus subtilis

Abstract

The aim of this study was to elucidate the mode of action of two antimicrobial compounds, nisin, which is hydrophilic, and the lipophilic compound carvacrol. For that purpose, both antimicrobials were loaded into Oil-in-/Water nanoemulsions, and their antimicrobial activity against Bacillus subtilis was investigated. The experimental results indicated that the O/W nanoemulsions loaded with both, nisin and carvacrol, having Sauter mean diameter (d 3,2) of around 120 nm, were considerably stable under the conditions investigated (up to 1 week storage at room temperature). The interfacial tension between nisin aqueous solutions and soybean oil could be reduced up to 12 mN/m, as compared to that of pure water and soybean oil (21 mN/m), so that demonstrating the potential of nisin to be used as emulsifier. The results obtained for O/W nanoemulsions loaded with both antimicrobial compounds indicated a reduction of nearly two log cycles (around 100 times) on B. subtilis population upon incubation for 24 h, compared to the blank (10 mM phosphate buffer).