Modifying hen egg-white lysozyme into amyloid fibrils with enriched β-sheets improved antimicrobial activity against...

The antimicrobial activity of hen egg-white lysozyme (HEWL) can be improved by various modifications. However, the antimicrobial mechanisms of modified HEWL need further investigation. Here, HEWL protein was modified at 57 °C in glycine solution of pH 2.2 into amyloid fibrils with fibrillar ultrastructure and greatly increased β-sheets. The relative enzyme activity of HEWL amyloid fibrils decreased by 35.5 %. HEWL fibrils significantly improved antimicrobial activity against the foodborne pathogenic bacteria, including V. parahaemolyticus, A. hydrophila and M. luteus. The minimum inhibitory concentrations (MIC) were 125 μmol/L for V. parahaemolyticus, 62.5 μmol/L for A. hydrophila, and 0.025 μmol/L for M. luteus. Whereas MICs of native HEWL were > 500 μmol/L for V. parahaemolyticus and A. hydrophila, and > 10 μmol/L for M. luteus. Furthermore, HEWL fibrils damaged the cell walls and membranes of the three bacteria after 3 h treatment, causing alkaline phosphatase (AKP) leaking from the bacterial cell walls, and lipopolysaccharides (LPS) releasing from the outer membranes of V. parahaemolyticus and A. hydrophila. Our results revealed that the improved antimicrobial activity of modified HEWL was due to the conformational change into macromolecule with β-sheets. The modified HEWL with enriched β-sheets could be potentially applied to food packaging and animal feeding.