Lead Adsorption Characteristics And Mechanism Of Lactic Acid Bacteria With Potential Probiotic Characteristics

Heavy metals pollution is one of the hot issues in food safety.The use of food grade lactic acid bacteria to adsorb heavy metals has become a new research area.In this study to comprehensively evaluate the feasibility of Pb higher adsorption strains as Pb absorbent by analyzing their Pb adsorption characteristics and mechanism and evaluating their potential probiotic characteristics.1.The 26 high-tolerance lead LAB strains as the research subjects,to domesticate the strains with the initial Pb concentration was 3600 mg/L and 1200 mg/L as gradual gradient.Finally,15 strains with good growth condition,stable character and tolerant concentration of 6000 mg/L were finally obtained.F-f-3,F-e-3,9-b-1,10-a-1 as high adsorption strains were selected based on the adsorption efficiency,which were conducted to investigate the influences of pH,the initial Pb ion concentration,cell concentration,adsorption time,adsorption temperature.Results showed:?1?As the pH value increased,the adsorption rate and the adsorption quantity also increased,p H 6.5 was the optimum pH for Pb adsorption process;?2?As the cell concentration increased,which would decrease adsorption capacity and increase efficiency;?3?As initial Pb²⁺concentration increased,the adsorption quantity increased but the adsorption rate decreased;?4?Low temperature has an influence on adsorption progress,with the temperature increased,the adsorption rate and the adsorption capacity also increase;?5?With the increase of adsorption time,the adsorption and adsorption rate also gradually increased,which would reach equilibrium after 60 minutes.The 4 strains was measured by 16S rRNA identification,to determine that all 4 strains were Pediococcus pentosaceus.2.To evaluate the potential probiotic properties of 4 high-adsorption Pb strains.When the p H<3.5,the growth of the strain is inhibited.When the concentration of bile salt is 0.3%,the growth of the strain is also inhibited.When the concentration of NaCl>5%,the inhibitory effect is obvious.The four strains were tested for their antioxidant capacity and found that the strains had good effects in scavenging DPPH free radicals,hydroxyl radicals,superoxide anion,and anti-lipid peroxidation,and the group significantly differed from cell-free extract group?P<0.05?.3.To clarify the adsorption mechanism of Pediococcus pentosaceus 9-b-1,desorption experiment,Fourier transform infrared spectroscopy?FTIR?and scanning electron microscopy?SEM?were combined to analyze the changes of cell microstructure and morphology characterize the interaction of bacteria and Pb.Weissella cibaria 8-b-2,a low-adsorption Pb strain,was used as control.-COOH?-NH₂?-OH?-H₂PO₄ and-CO were involved in biosorption process,and the lead ions had toxic effects on the cells,the cell structure is destroyed,a large number of precipitated substances on the cell surface.Pb adsorption mechanisms of LAB might include complexation,ion exchange,electrostatic interaction and intracellular diffusion.