Antibacterial Stability of Novel Nisin/Carboxylic Curdlan Complexes

Nisin is a widely used natural antibacterial peptide in the food industry. However, its instability limits its practical application in food preservation. In this study, the antibacterial activity of previously built nisin/carboxylic curdlan (C6-Cc) complexes were tested against Gram-positive bacteria: Staphylococcus aureus. The results revealed that when the mass ratio of C6-Cc to nisin was 1:8 (C6-Cc: nisin, w/w), the nisin/C6-Cc complexes exhibited strong antibacterial stability over the pH range of 1-4, with inhibition zone diameters ranging from 11.5 to 13.0 mm and a minimum inhibitory concentration (MIC) of 0.71 mg/mL. Notably, the complexes also maintained good thermal stability even at 121 °C. Furthermore, the complexes with a mass ratio of 1:8 (w/w) showed superior physicochemical stability under low-pH conditions (pH < 5) within the salt concentration of 0-100 mM, and the stable temperature ranged from 25 to 121 °C. Twenty-eight days of storage had no significant impact on its antibacterial or physicochemical stability. These findings suggest that the nisin/C6-Cc complexes will have broad application prospects in food bio-preservation.