Effect of photodynamic inactivation of Escherichia coli by hypericin

The present study has focused on the effects of hypericin (Hyp) based photodynamic inactivation (PDI) of Escherichia coli ( E. coli ). To evaluate the efficiency of Hyp based PDI of E. coli , single factor experiments and response surface optimization experiment were conducted to obtain the optimum parameter values (36 µM Hyp, 5.9 J cm −2 light dose: 16.4 mW cm −2 , 60 W, 260 s, 590 nm and 68 min incubation time) and finally achieved a 4.1 log CFU mL −1 decrease of E. coli . Cell-Hyp interaction and intracellular reactive oxygen species (ROS) level were detected by fluorescence spectrometric photometer. Data indicated that Hyp possessed a strong ability to bind with cells. In addition, a significant increase was observed in intracellular ROS level after Hyp-based photosensitization treatment. Therefore, Hyp-based photosensitization seems to be a promising method to efficiently inactivate E. coli . It is expected to be a safe, efficient, low cost and practical method which can be applied in the field of food safety.