Factors involved in Bacillus spore's resistance to cold atmospheric pressure plasma

In this study factors involved in spore resistance to cold atmospheric pressure plasma (CAPP) were investigated. Therefore, wild-type Bacillus subtilis spores and isogenic mutant strains, PS578 lacking the genes encoding the spore's two major small acid soluble proteins (SASPs), FB122 being unable to synthesize dipicolinic acid (DPA) during sporulation and PS3328 lacking the outer spore coat, were CAPP treated using different process gasses (air, N-2, O-2, CO2). Obtained inactivation depended on the process gas; highest inactivation efficiency was obtained with N-2-plasma. The results indicated that SASPs contribute in general to spores' CAPP resistance. DPA and outer spore coat were also important in the protection against UV photons, however, the protective effect was not so pronounced as for SASPs. Furthermore, they contributed in resistance against generated ozone. Bacillus atrophaeus spores, the surrogate for chemical and irradiation sterilization, showed over all a lower resistance to all tested CAPPs. Industrial relevance: The application of cold atmospheric pressure plasma (CAPP) is an emerging low temperature technology for the inactivation of bacterial spores on different surfaces, such as food products as well as food contact surfaces and packing material. The results presented in this study help to understand the inactivation mechanisms and also the factors involved in the high resistance of bacterial spores to CAPP. This knowledge could be useful to optimize the plasma process for the decontamination of various surfaces in the food industry.