Thermal stability of bacteriocin nisin in polylactide-based films

Abstract

This work investigates the thermal stability of bacteriocin nisin in polylactide (PLA) and polylactide/polyethylene glycol (PLA/PEG) blends at temperatures of 90 °C–180 °C. The samples were prepared by solvent cast technique and characterized according to their mechanical and thermal properties. Research on the thermal stability of nisin in the PLA and PLA/PEG systems was carried out by exposing the given films to various temperatures (90 °C, 120 °C, 160 °C, and 180 °C) for a duration of up to 48 h. Assessment of the antibacterial activity of the samples was carried out by the agar diffusion method against Micrococcus luteus, while structural analysis involved the use of high-performance liquid chromatography with mass detection. Structural changes in the polymer matrix were evaluated by gel permeation chromatography and scanning electron microscopy. The results showed that nisin retained almost 70% of its antimicrobial activity in the PLA matrix, even after treatment at 160 °C for 15 min. The presence of PEG significantly enhanced the degradation of nisin above 120 °C. © 2018 The Authors