Effect Of Calcium Ion On Disinfection Performance Of Tea Polyphenols

In recent years,the national standards for drinking water quality have been gradually improved.Drinking water disinfection is the most basic way to ensure the safety of drinking water.However,at present,there is no disinfection method that can guarantee disinfection efficiency and is absolutely healthy and safe.Tea polyphenols have the potential to develop into a new type of disinfectant for drinking water due to their green and efficient sterilization properties.There has been some progress in the research on the application of tea polyphenols disinfection,but the lack of environmental factors in water has affected tea polyphenols disinfection.Studies have shown that metal ions may change the biological activity of tea polyphenols.Epigallocatechin gallate?EGCG?is the main component that promotes the antibacterial effect of tea polyphenols.In this paper,EGCG is used as a representative of the antibacterial properties of tea polyphenols.The representative of common metal ions,explore the effect of Ca²⁺on the disinfection performance of tea polyphenols,and analyze the mechanism of its influence,to provide a theoretical basis for the application of tea polyphenols in drinking water disinfection.The test explored the effect of Ca²⁺on the EGCG inhibitory activity by detecting the size of the EGCG inhibition zone and the minimum inhibitory concentration and the growth curve of Escherichia coli?E.coli?in the presence of Ca²⁺.Active,high concentration of Ca²⁺?6-10mM?can promote the antibacterial activity of EGCG.Under the condition of high concentration of Ca²⁺,growth inhibitory effect of EGCG on E.coli is significantly enhanced,and there is a significant decay period on the growth curve of E.coli.However,the small-scale proliferation of E.coli in the late growth period indicates that high concentration of Ca²⁺has accelerated the inhibition of EGCG Efficiency,but bacterial recovery may occur.In the presence of Ca²⁺,EGCG still has continuous disinfection effect,but high concentration of Ca²⁺will cause the decay rate of EGCG to accelerate,which may be the reason for its increased EGCG disinfection efficiency.By examining the bacterial inactivation rate and damage rate,it can be known that low concentration of Ca²⁺will reduce the inactivation rate of EGCG against E.coli,and high concentration of Ca²⁺can increase the killing ability of EGCG against E.coli,but it will produce more damage bacteria,which may bring New security risks.The test tested the diameter of bacteriostatic circle and the minimum inhibitory concentration of EGCG under Ca²⁺environment.The results showed that the low concentration of Ca²⁺?1-5mM?reduced the antibacterial activity of EGCG,and the high concentration of Ca²⁺?6-10mM?against EGCG has a certain role in promoting.In the Ca²⁺environment,EGCG still has a continuous disinfection effect,but the attenuation rate of EGCG in the high-concentration Ca²⁺environment is significantly accelerated.Through the growth curve of E.coli,it was found that EGCG significantly increased the growth inhibition effect of E.coli under the high-concentration Ca²⁺environment.However,E.coli had a small growth in the late growth period,and the phenomenon of bacterial recovery may occur.In addition,the detection of bacterial inactivation rate and damage rate shows that low concentration of Ca²⁺will reduce the inactivation rate of EGCG against E.coli.High concentration of Ca²⁺can improve the killing ability of EGCG against E.coli,but it will produce more damage bacteria,which may bring new security risks.The test examined the structural changes of EGCG under the Ca²⁺environment,and the results showed that the effect of Ca²⁺on the antibacterial activity of EGCG may not be caused by the complexation of Ca²⁺with EGCG.In order to further explore the mechanism of Ca²⁺on the disinfection of EGCG,the transmission electron microscope was used to observe the obvious deformation and destruction of the cell wall membrane structure of E.coli treated with EGCG,while the Ca²⁺environment caused only local damage to the cell wall of E.coli and the permeability of the cell membrane.Significantly increased,there was a clear aggregation of cytoplasm,which showed that Ca²⁺weakened the destruction of EGCG on the microstructure of E.coli,and may promote the primary attack point of EGCG to exert antibacterial effect from cell wall membrane to intracellular substance.In addition,Ca²⁺may promote the leakage of intracellular glucose by increasing the permeability of the bacterial wall membrane,thereby affecting the metabolism of E.coli,inhibiting ATP consumption,and promoting EGCG to exert a bacteriostatic effect.In order to further explore the destructive effect of EGCG in bacteria under Ca²⁺environment,the test detected the changes of active oxygen,antioxidant system and oxidative stress response in E.coli and then analyzed the oxidative damage inside E.coli.The test results showed that E.coli in Ca²⁺environment The increased permeability of the cell wall membrane generally allows EGCG to enter the cell smoothly.EGCG uses self-oxidation to promote the increase of superoxide anion and hydrogen peroxide content in E.coli to increase the level of active oxygen.However,EGCG has a certain inhibitory effect on the antioxidant enzymes and antioxidant substances in the anti-oxidation system,which causes the active oxygen level in E.coli to exceed the antioxidant effect,which in turn causes oxidative damage to E.coli,but Ca²⁺stimulates the oxyR gene,dps gene and soxS gene expression reduces the damage of EGCG to bacterial DNA,and may activate the efflux pump to cause E.coli to develop resistance to EGCG,which in turn produces disinfection and damage bacteria.