Antibacterial activity and action mechanism of microencapsulated dodecyl gallate with methyl-β-cyclodextrin

The application of dodecyl gallate (DG) is limited due to its poor stability and water-solubility. A new compound of DG microencapsulated with methyl-beta-cyclodextrin (M beta CD), M beta CD-DG was produced, and the inhibition effects of M beta CD-DG against three common foodborne pathogens (Staphylococcus aureus, Bacillus cereus and Bacillus subtilis) were investigated in the study. The antioxidant activity of M beta CD-DG was determined by the DPPH method (EC50 = 4.515 +/- 0.5 mu g/mL). The minimum inhibitory concentration (MIC) of M beta CD-DG against these bacteria were 0.11, 0.06 and 0.06 mg/mL, and minimum bactericidal concentration (MBC) were 0.22, 0.11 and 0.11 mg/mL, respectively. The MICs remained steady under different pH values (3.0-9.0) and temperatures (4 and 25 degrees C), indicating that the anti-bacterial effect of M beta CD-DG was independent of pH and temperature. Measurements of permeability of cell wall and membrane, membrane potential, release of cellular contents and observation of cell morphology were carried out to explore the antibacterial mechanism of M beta CD-DG. The results indicated that M beta CD-DG inhibited S. aureus by increasing the permeability of cell membrane and leakage of cellular contents without obvious cell morphological changes. M beta CD-DG may kill B. cereus and B. subtilis by damaging the cell wall and cytoplasmic membrane to make the release of cellular contents. As a novel preservative, M beta CD-DG is more efficient than DG and common chemical additives, and is thus worthy of further exploitation in food industry.