Study On The Lethal Effect Of Basic Amino Acids Lysine And Arginine Assisted Microwave On Escherichia Coli

As an efficient heating technology,microwave has been widely studied in the field of food sterilization.Under microwave field,it is necessary to study the gain mechanism and related reactions in the process of microwave sterilization because of the microwave sensitivity of some small molecules in food components.In this study,Escherichia coli was used as the target strain,and the leaching rate of basic amino acid lysine and arginine to Escherichia coli was determined by microwave sterilization.The effects of amino acid addition on the subcellular structure of Escherichia coli were investigated.The mechanism of basic amino acid and microwave synergistic disinfection was preliminarily studied from the electromagnetic angle.The effects of amino acid side chain and acidity on the bactericidal effect were discussed.The main contents of the thesis are as follows:(1)Bactericidal effect of basic amino acids assisted microwave on Escherichia coli.The results showed that arginine and lysine could significantly improve the inactivation of E.coli by microwave irradiation based on the evaluation of its own bacteriostatic effect.In the 0.5 to 2.5% amino acid concentration range,the bactericidal effect was proportional to the amino acid concentration,and with the same concentration and the same microwave treatment,the effect of arginine was significantly greater than that of lysine.Meanwhile,a comparison of traditional sterilization(water and oil bath)and microwave sterilization indicating that microwave sterilization in addition to thermal effects,there existed microbial specificity that can not only explained by temperature increase.The synergistic coefficients of lysine and arginine with microwave were 1.52 and 3.45 indicated the synergistic bactericidal action against Escherichia coli.(2)Effects of alkaline amino acids on subcellular structure of Escherichia coli under microwave irradiationThe surface morphology of E.coli cells treated with lysine and arginine under microwave irradiation was observed by scanning electron microscopy,showed the basic amino acids and microwave treatment could cause cell structure damage on E.coli.The study of electrolyte and protein leakage showed that alkaline amino acids and microwave treatment damaged the cell membrane of E.coli.(3)Electromagnetism mechanism of bactericidal effect of basic amino acids under microwave irradiationThe electromagnetic properties of alkaline amino acids were measured by means of vector network analysis,including dielectric properties,electrical conductivity characteristics and absorbing properties.The results showed that with the increasing temperature,the solution viscosity and the relaxation time decrease,causing an increase of the dipole moment,and the dielectric constant and dielectric loss decrease.Fix the temperature,the dielectric loss of amino acids were proportional to the concentration.The conductivity was proportional to the concentration and temperature of the amino acid solutions.Based on the correlation principle of impedance matching,it was proved that the absorption characteristics of basic amino acids were related to the frequency,concentration and thickness of absorbing layer,and the effect of sterilization was consistent with that of electromagnetism.(4)Acid base environment and group mechanism of bactericidal effect of basic amino acids under microwave irradiationAccording to the environmental and structural factors of the synergistic bactericidal process,the mechanism of microbial sterilization was explored by adjusting the environment and comparing the structural analogues.The results showed that the reason of moderate acid-base offset to increase the bactericidal effect was the change of the charge content of the solution.However,arginine structural analogues Arginine-like analogue citrulline was selected to demonstrate the correlation between synergistic bactericidal activity and amino specific gravity in amino acids,the results showed that the ionization of the basic amino acids during the structural transition and the change of the ionic characteristics of the solution significantly affected the microwave sterilization of the system.In general,the basic amino acid lysine and arginine assisted microwave treatment significantly promoted the lethality of E.coli.The bactericidal effect of basic amino acid and microwave was related to the destruction of microbial cell membrane structure.The dielectric and conductivity of basic amino acid aqueous solution are dependent on the temperature and concentration of amino acids,and had good microwave absorption effect.The bactericidal effect of basic amino acids and microwave was related to the acid-base properties of basic amino acids,but independent of the proportion of amino-group contained in basic amino acids.