Photodynamic inactivation of Listeria monocytogenes using a natural aggregation-induced emission photosensitizer and its application in salmon preservation

Photodynamic sterilization has been regarded as a promising alternative to conventional antibacterial approaches. However, the photodynamic efficiency of conventional photosensitizer is often compromised by aggregation-induced quenching effects. Photosensitizers, especially natural products, with aggregation-induced emission (AIE) properties open a new avenue for photodynamic sterilization. Herein, we investigated the photodynamic antibacterial performance and mechanism of the AIE-type natural product of berberine (BBR) against Listeria monocytogenes (L. monocytogenes). The bactericidal effect was assessed through the determination of minimum bactericidal concentration and implementation of anti-biofilm experiments. The results showed that BBR can significantly suppress the proliferation of L. monocytogenes and can efficiently remove the L. monocytogenes-derived biofilm in a concentration-dependent trend. The mechanism of killing L. monocytogenes has been speculated based on bacterial morphology characterization, viability staining results, enzyme activity assays, DNA electrophoresis analysis, and molecular docking. The excellent anti-bacterial activity of BBR mediated photodynamic process may account for its abilities to the irreversibly disruption of bacterial membrane, inhibition of intracellular enzyme activity and decomposition of intracellular DNA molecules. We also demonstrated that BBR embedded sodium alginate/chitosan packaging film is feasible to maintain the freshness of salmon under light illumination by inhibiting the bacterial proliferation.