The combined antimicrobial activity of α-lactalbumin and thymol against Escherichia coli and Staphylococcus aureus

Thymol showed good antimicrobial activity, however, the poor aqueous solubility limits it to apply in food industry. alpha-Lactalbumin can be used to delivery hydrophobic molecules, then enhancing their biological activities. The study investigates the potential of alpha-lactalbumin to expand the application range of thymol, further to evaluate the antimicrobial activity of the alpha-lactalbumin-thymol complexation. Multi-spectroscopy techniques and computational simulations have confirmed the successful complexation, driving mainly by van der Waals force. The alpha-lactalbumin-thymol complexation exhibited the superior antimicrobial activity than thymol against Escherichia coli and Staphylococcus aureus, as indicated by lower or comparable minimum inhibitory concentration (336 mu g/mL and 224 mu g/mL, respectively), fewer colony forming units, and larger inhibition zone diameters. Furthermore, alpha-lactalbumin enhanced the degree of membrane damage by thymol. The complexation preserved no obvious cytotoxicity against HeLa cells. This study indicates that the alpha-lactalbumin-thymol complexation chelates hold promise as natural antimicrobial agents in the food processing industry.