Experimental Study On Sterilizatior Of Escherichia Coli By Atmospheric Pressure Cryogenic Plasma Combined With Photocatalysis

Atmospheric pressure cryogenic plasma(APCP)has attracted extensive attention and research in the field of sterilization due to its low macro-temperature and high reactivity.However,the sterilization time of APCP is from tens of seconds to tens of minutes,and the efficiency of sterilization has the potential to improve.At the same time,part of the energy in APCP is lost in the form of photons,and its utilization rate of energy still needs to be improved.Photocatalysis utilizes photons in atmospheric low-temperature plasma as excitation source and produces plenty of reactive oxygen species to enhance the sterilization efficiency of APCP.The conversion of light energy into chemical energy of reactive oxygen groups improves the sterilization efficiency and the energy utilization of atmospheric low temperature plasma.The application of atmospheric pressure cold plasma combined with photocatalysis(APCPCP)in sterilization needs to be studied urgently.In this paper,an experimental platform of APCPCP in sterilization is built.The physical characteristics of APCP are diagnosed.Then,the inactivation effect and sterilization mechanism of APCP are explored.The specific contents and results are as follows:(1)The effects of voltage,frequency,flow rate and photocatalysis on APCP jet length were investigated.The results showd that the length of the jet increased with the increase of.voltage,and then decreased with the increase of flow rate.The frequency and photocatalysis had no effect on the length of the jet.The spectrum of APCP was detected,and the characteristic lines of OH,N2,He,singlet oxygen atom and trilinear oxygen atom are founded.The photocatalysis process didn’t affect the emission spectrum of APCP Crystal violet spectrophotometry showed that APCPCP produced more reactive oxygen species.(2)The inactivation of E.coli by APCPCP was studied.The effect of different voltage,frequency,flow rate and catalyst on the inactivation of E.coli by APCPCP was investigated through colony counting method.The results showed that the photocatalysis process enhanced the sterilization effect of APCP.With the increase of voltage,frequency and flow rate,the survival rate of E.coli treated by APCPCP decreased continuously.Scanning Electron Microscope(SEM)was taken to detect the micromorphology change of E.coli under APCPCP treatment.The results showed that E.coli treated by APCP was in a viable but non-culturable state,while the structure of E.coli treated by APCPP under the same conditions was ruptured.APCPCP had a more powerful killing effect on E.coli.(3)The mechanism of APCPCP sterilization was explored by detecting the differences of leakage protein,metabolic capacity and reactive oxygen species production under APCP and APCPCP treatment.The experimental results showed that the concentration of leakage protein in E.coli solution treated under 18 kV APCPCP for 15 seconds was 0.115 μg/μL,which was similar to that in the 30s treatment of 19kV APCP.If the experiment was carried out under the same conditions,APCPCP caused more protein leakage.Under APCP treatment,the number of E.coli with metabolic ability was more than that of colonies,while the number of E.coli with metabolic ability was approximately the same as that of colonies under APCPCP treatment.This indicated that APCP treatment caused some E.coli entering VBNC state,while APCPCP treatment inactivated E.coli more poxwerfully.The study further improved the sterilization efficiency and energy utilization rate of APCP,verified the feasibility of APCPCP and provided valuable experimental experience and theoretical basis for the application of atmospheric low-temperature plasma combined photocatalysis in the field of sterilization.