Antibacterial mechanism and application of ε-polylysine conjugation with dextran.

e-Polylysine-dextran conjugate is a compound conjugated with e-polylysine (PL) and dextran through the Maillard reaction. The antimicrobial activity of PL-dextran conjugate was investigated using six Gram-positive and Gram-negative bacteria. The integrity of the cell membranes of the representative bacteria was determined by the amount of intracellular components released from the cells. It was found that the PL-dextran conjugate retained most of the original antimicrobial activity of PL. When treated with PL or the PL-dextran conjugate, the amount of releasing materials at absorbance of 260 nm quickly increased in both Gram-negative and positive bacteria, but the absorbance values were different due to the difference in cell structures. Furthermore, an outer membrane (OM) permeability assay was performed by fluorescent probe 1-N-phenylnaphthylamine (NPN). The results showed that PL or PL-dextran conjugate rapidly increased the NPN uptake. In addition, the preservative effect and the emulsifying properties of the PL-dextran conjugate were also observed when it is applied in coffee whitner. These findings indicate that the PL-dextran conjugate can be applied in the food processing industry.