Biofilm inhibition and eradication activity of citral and borneol against foodborne bacteria

Biofilms growing on food surfaces, packaging, equipment and processing environments bring huge risks to food safety and result in economic losses. Natural components are receiving increasing interest as “green” antimicrobial agents due to their biocompatibility, broad-spectrum antimicrobial properties, and antibiofilm potential. As a traditional adjuvant in Chinese medicine, borneol has the potential to enhance citral’s antibiofilm efficacy. In this study, the antibiofilm activities of citral, borneol, and the combination citral and borneol (BC) against various foodborne bacteria were evaluated using multiple techniques. Light microscopy, crystal violet (CV) staining, and the 2,3-bis (2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylaminocarbonyl]-2H-tetrazolium hydroxide (XTT) assay were employed to monitor biofilm formation. Additionally, biofilm eradication was assessed against Staphylococcus aureus and Escherichia coli biofilms grown on polycarbonate membranes. Protein leakage was measured, and field emission scanning electron microscopy (FESEM) was used to examine cell membrane integrity. Results showed that borneol and citral acted synergistically to inhibit biofilms. Borneol, citral, alone or together inhibited biofilm formation in a concentration dependent manner, and they have the ability to inactivate or kill at least 90.7 ± 1.9 % bacteria in preformed biofilms. Both borneol and citral disrupted the membrane integrity of the bacteria, increased permeability, and ultimately led to cell death. These findings suggest that the combination citral and borneol has the potential to be developed as a food preservative or bactericidal agent for controlling foodborne bacterial contamination.