Berberine-loaded nanoemulsions as a natural food preservative; the impact of femtosecond laser irradiation on the antibacterial activity

There is a growing concern among food safety regulators, the food industry, and consumers about foodborne illnesses. To improve food safety and increase shelf life, it is necessary to use natural preservatives. Natural antimicrobials are safer than artificial preservatives because they can prevent microbial resistance while also meeting consumers' demands for healthier food. This study used Berberine to enhance the antibacterial activity of <i>Satureja Khuzistanica</i> essential oil nanoemulsions (SKEO NE) against <i>Staphylococcus aureus</i> (<i>S. aureus</i>) bacteria, making them a promising option as preservatives. Response Surface Methodology (RSM) was employed to determine the optimized Berberine loaded SKEO NE (Berberine/SKEO NE), resulting in a mean droplet size of 88.60 nm at 6.91, 3.21, and 0.08% w/w of surfactant, essential oil, and Berberine, respectively. Berberine utilization in SKEO NE has led to an increase in antibacterial activity. The nanoemulsion samples significantly ruptured the <i>S. aureus</i> bacterial cell membrane, rapidly discharging cell contents. The use of a microfluidic system in tandem based on the conventional approach significantly accelerated this process. Enhancing the interaction between nanodroplets and the bacterial membrane can be achieved through the nanoemulsification process of EOs, which involves modifying their surface characteristics. This enhancement is particularly pronounced when employing microfluidic systems due to their substantial contact surface area. We investigated the potential of using femtosecond laser irradiation at a wavelength of 1040 nm to augment the antibacterial action of nanoemulsions. The combined treatment of laser and nanoemulsions significantly increased the antibacterial effect of nanoemulsions by approximately 15% for each bacterium, suggesting the potential utility of this treatment to bolster the antibacterial activity of nanoemulsions. Bacteria were trapped using optical tweezers for up to 20 min, with bacterial destruction observed starting at 3 min and exhaustive destruction evident after 20 min.