Antibiofilm effect of nisin and clove oil (Syzygium aromaticum) on Escherichia coli biofilms

The demand for natural food preservatives is growing and cloves have been historically used both as a flavour enhancer and as a means of food preservation, largely due to the presence of the antimicrobial compound, eugenol. The study aimed to investigate the combinatory effects of nisin and clove essential oil on the inhibition of E. coli growth and biofilm formation, a persistent problem in food processing surfaces. The study obtained clove essential oil through steam distillation and evaluated antibacterial and antibiofilm properties using the Kirby-Bauer method and photometric assays with a 96-well plate. The results showed that lower concentrations of both nisin and clove essential oil effectively inhibited the formation of E. coli biofilms. Nisin alone at 250IU resulted in a 97 % inhibition of E. coli biofilms, while clove oil at a concentration of 6 mg/ml showed an 87 % inhibition. When combined, the two compounds exhibited a synergistic effect, resulting in E. coli biofilm inhibition of 95 %. This synergistic activity may be due to cross-activity between nisin and the active components of clove extract, including eugenol and eugenol acetate, which have shown potential antimicrobial and antibiofilm effects. Therefore, this study highlights the potential of using lower concentrations of nisin and clove essential oil as a combined hurdle in inhibiting biofilm formation in E. coli, which can be useful in disinfecting food processing surfaces.