Epsilon-polylysine based magnetic nanospheres as an efficient and recyclable antibacterial agent for Alicyclobacillus acidoterrestris

In this work, polyacrylic acid modified ferroferric oxide (Fe3O4-PAA) was synthesized via a one-step hydrothermal method. The magnetic nanospheres modified with carboxyl groups were combined with epsilon-polylysine (EPL) via an EDC/NHS coupling reaction to obtain Fe3O4-PAA-EPL nanospheres. Fe3O4-PAA-EPL was employed as an antibacterial agent against Alicyclobacillus acidoterrestris and characterized by XRD, FTIR, XPS, VSM, SEM and TEM techniques. Experimental results showed the minimum inhibition concentration (MIC) of Fe3O4-PAA-EPL against A. acidoterrestris was 1.25 mg mL−1. Furthermore, A. acidoterrestris treated with Fe3O4-PAA-EPL nanospheres obviously lysed. Morphological analysis of bacteria supported by SEM indicated that the cell membrane of A. acidoterrestris was damaged, revealing that Fe3O4-PAA-EPL is an effective antibacterial agent. Additionally, the nanospheres with excellent magnetism can be simply separated from a reaction system via an external magnet. The construction of magnetic nanospheres with satisfactory antibacterial activity provides an effective and new method to control A. acidoterrestris.