Efficacy of Pectobacterium carotovorum subsp. carotovorum inactivation using ultraviolet C light-emitting diodes: Investigation of inactivation efficacy toward planktonic and biofilm cells on the stainless steel surfaces of cutting machines

Abstract

The presence of Pectobacterium carotovorum subsp. carotovorum (P. carotovorum) in kimchi cabbage (Brassica rapa L. subsp. pekinensis) negatively influences kimchi quality. Accordingly, inactivation processes to effectively control spoilage caused by plant bacteria, including P. carotovorum, are crucial for extending the shelf life of kimchi. In this regard, ultraviolet C light-emitting diode (UVC-LED) technologies are increasingly attracting attention as non-thermal and non-contact sterilization technologies and are also considered as alternatives to chemical disinfectants. In this study, we investigated the efficacy of the inactivation of P. carotovorum planktonic and biofilm cells that cause cabbage soft rot disease using the UVC-LED treatment technology as a potential disinfection method for a safe kimchi manufacturing process. A biofilm was formed on the surface of a stainless-steel cutter knife using the recommended CDC biofilm reactor system and thereafter, exposed to a range of UVC-LED intensities. Our results indicated that P. carotovorum planktonic and biofilm cells to UVC-LED irradiation at 9.0 mJ/cm2 resulted in >5.0 and >2.0 log10 inactivation, respectively. Additionally, the P. carotovorum planktonic and biofilm cell inactivation kinetics fitted the non-linear reduction curve. The UVC-LED treatment was also found to be highly efficient in eliminating planktonic cells, showing consistency with the Weibull and Weibull tailing models for planktonic cells.