Characteristic Analysis Of Lactobacillus Adsorbing Cadmium

Cadmium pollution has become a public safety and hygiene problem that seriously threatens people's health.Cadmium exposure can cause damage to various tissues and organs such as blood,liver and kidneys.A strain of Lactobacillus plantarum CCFM8610,which has a strong adsorption effect on cadmium,was selected in the preliminary research.It can be used in diet and reduce the toxicity of cadmium to human body.Therefore,it is necessary to carry out the adsorption mechanism of Lactobacillus plantarum to cadmium.Analysis provides a theoretical basis for its better application in the prevention and treatment of body cadmium toxicity.This subject hopes to systematically explain the heavy metal adsorption mechanism of Lactobacillus and try to find the specific adsorption site of cadmium on Lactobacillus.The main research results of this subject are as follows: First,the six species of strains including Lactobacillus fermentum,Lactobacillus casei,Lactobacillus reuteri,Lactobacillus helveticus,Lactobacillus rhamnosus,Lactobacillus plantarum,etc.were investigated for cadmium adsorption capacity,and experiments were conducted The results showed that different species of Lactobacillus did not show significant differences in cadmium adsorption,and there were significant differences between the same species of Lactobacillus strains.The adsorption kinetic curve of cadmium ion by Lactobacillus shows that adsorption is a fast and efficient process,reaching 90% of the equilibrium adsorption capacity at 60 min,and reaching the equilibrium value in about 100 min.The quasi-second-order kinetic equation fits the kinetic experimental data well?R2 = 0.9861?,indicating that the cadmium adsorption by Lactobacillus is the result of a physical and chemical reaction.The correlation analysis between the specific surface area of Lactobacillus and the cadmium adsorption capacity showed that there was no correlation between the specific surface area and the cadmium adsorption capacity.In order to eliminate the errors caused by the differences in metabolism and bacterial structure of different strains,only Lactobacillus plantarum was selected for the experiment.Experiments found that there are still significant differences in the cadmium adsorption capacity of Lactobacillus plantarum with the same specific surface area,indicating that there may be some surface characteristics or specific substances in Lactobacillus plantarum that cause the difference in adsorption capacity.Next,the correlation analysis between the cadmium adsorption capacity of Lactobacillus plantarum and the two important surface characteristics of hydrophobicity and Zeta potential were carried out.The experimental results found that there is no correlation between hydrophobicity and cadmium adsorption capacity.Lactobacillus plantarum Zeta potential and cadmium adsorption capacity correlation analysis calculated p value is 0.0364,r value is 0.5102,Zeta potential and cadmium adsorption capacity have a moderate correlation,indicating that electrostatic interaction is an important mechanism of cadmium adsorption.The cadmium adsorption group was analyzed by infrared spectroscopy,and it was found that the cadmium adsorption related groups may be: amide group,alkyl group and phosphoroxy group.The adsorption sites of cadmium were explored through component stripping,and it was found that cadmium was mainly combined on the surface of the cell wall and inside the cell wall.After removing the surface protein,the cadmium adsorption capacity of most Lactobacillus plantarum changed significantly,indicating that the surface protein can affect the adsorption of cadmium on the cell surface.Component stripping experiments show that cadmium is more likely to bind to the surface of the cell wall after removing the surface protein.After removing the surface protein,there is no significant change in the morphology and surface of the bacteria,and the survival rate after removing the protein is above 80%,indicating that it is indeed caused by the surface protein.Adsorption of cadmium.There is no correlation between the surface protein content of Lactobacillus plantarum and the cadmium adsorption capacity,indicating that there may be some special proteins that affect cadmium adsorption.By HPLC-ICP-MS?High performance liquid chromatography-inductively coupled plasma-mass spectrometry?trying to separate the cadmium-adsorbed protein,a cadmium peak appeared at 10 minutes.Finally,through iTRAQ?Isobaric tags for relative and absolute quantification?,the high cadmium adsorption strain CCFM8610 and the low adsorption strain VHuNHHMY12L1 were selected,and their surface proteins were extracted for proteomics analysis.A total of 285 differential proteins were detected,which were clearly located in the cell wall and cell membrane.There are 110 proteins in total.There are 27 cell wall and extracellular proteins and 45 cell membrane proteins that are more expressed in highly adsorbed strains.By consulting the literature,it is found that the protein types related to cadmium adsorption are extracellular protein,peptidoglycan metabolism,teichoic acid metabolism-related protein,metal transporter,amino acid ABC transporter and lipoprotein.Proteins rich in cysteine and methionine are considered to be the key proteins for cadmium binding.The number of cysteine and methionine contained in these proteins was analyzed,and three key proteins for cadmium adsorption were screened.They are the extracellular proteins Lp19₀886,Extracellular protein AVR82₁0195,amino acid ABC transporter oppA5.Integrating the conclusions drawn from the proteome,a diagram of the cadmium adsorption mechanism was obtained.