One-pot approach biosynthesis of nisin-conjugated zinc oxide nanoparticles using Bacillus subtilis ZBP4 with improved antibacterial activity

Abstract

AbstractBiosynthesis of nisin-conjugated zinc oxide nanoparticles (N-ZnONPs) using the supernatant of Bacillus subtilis ZBP4 was demonstrated using a single-step reaction. Various amounts of nisin (5, 10, 15 mg/mL) and 8 mM ZnSO4.7H2O were reacted in the cell-free supernatant of Bacillus subtilis ZBP4 at 33 °C for 48 h. Surface plasmon resonance peaks created by N-ZnONPs were measured at 341–342 nm with a UV-VIS spectrophotometer, and the band-gap energy was calculated as 3.38 eV, indicating the nano-conjugates acted as semiconductors. Transmission electron microscopy (TEM) images showed that the N-ZnONPs were pseudo-spherical with an average diameter of 23 nm. Fourier transform infrared (FTIR) spectra analysis confirmed the presence of nisin as well as other organic substances in the structure. N-ZnONPs had potent antimicrobial activity on Escherichia coli O157:H7 and Staphylococcus aureus; the minimum inhibition concentrations were 0.05 and 1 mg/mL, respectively. In addition, conjugation with nisin increased the long-term stability of nanoparticles when compared to unconjugated ZnONPs.