Non-thermal Plasma Inactivation of Bacillus Amyloliquefaciens spores

Inactivation of Bacillus amyloliquefaciens (BA) spores by non-thermal plasma (NTP) was investigated by studying inactivation kinetics and using attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR). ATR-FTIR is a useful tool to probe the biochemical and structural changes of spores after NTP treatment in order to better manipulate and optimize the parameters for NTP processing. The microdischarge generated by the dielectric barrier in our research has higher energy efficiency compared with a uniform glow discharge at atmospheric pressure and autoclave. The survival curve showed two phases with different spore inactivation rates and changes in surface topography of the spores assessed by atomic force microscopy (AFM) indicating that NTP treatment disrupted spore aggregates so that reactive species could reach and inactivate the bottom layers of spore films. Scanning electron microscopy (SEM) images showed that the spore surface was etched away after NTP treatment. Multivariate classification models based on Soft Independent Modeling of Class Analogy (SIMCA) were developed to identify the biochemical changes after NTP treatment. The absorbance of bands correlated to dipicolinic acid (DPA) ring decreased after NTP treatment indicating that DPA released and then reacted with reactive species generated by plasma, which was confirmed by NMR spectra. Also bands corresponding to protein structure changed after NTP treatment.