Isolation Of A Bacterial Stain Resistant To Heavy Metal Chromium(?) And Its Adsorption Conditions

Heavy metal pollution is closely related to the discharge of wastewater from industries such as metallurgy,paper making,pesticide production,pharmaceutical industry,paint and chemical manufacturing.The discharged sewage contains a variety of heavy metal ions,which not only poses great threats to the environment and many ecosystems,but also may endanger human health and life through the food chain accumulation.The source of heavy metal chromium?III?is mainly produced during the metal smelting process.The concentration of Cr?III?in the process of wastewater discharge can reach 10mg/L.However,the concentration of Cr?III?in drinking water cannot exceed 0.04 mg/L.Compared with other heavy metals,Cr?III?is less likely to be naturally degraded by the environment.Microorganisms play an important role in the control of environmental pollution caused by heavy metals.Compared to chemical methods and physical methods,microbial remediation has the characteristics of high efficiency,low cost and no pollution.However,most of the resistant strains are relatively weak in the ability to absorb chromium.Therefore,the screening of high-efficiency strains that are tolerant to metal chromium is of great significance for heavy metal pollution.In this study,a strain resistant to heavy metal Cr?III?was screened from seawater sludge of Fishery Terminal,Hai chang,Yantai.The optimal growth conditions of the strain were analyzed by experiments.By the usage of Response Surface Methodology?RSM?,we optimized the optimum adsorption conditions of the strain for heavy metal Cr?III?and determined the adsorption capacity of this stain.The adsorption kinetics equation for heavy metal Cr?III?was also analyzed.The detailed findings are as follows:1.The 16S rDNA primers were applied to sequence PCR amplification products and then construct a phylogenetic tree of the strain.By the analysis of 16S rDNA sequence and phylogenetic tree,the strain was named Pseudomonas putida SP-1.2.The influence of the external environment on the growth of the strain was explored from the composition of the medium,the pH,the salt concentration and the temperature.The optimum medium for the strain was LB liquid medium,the optimum pH was 7.0,the optimum salinity was 0.5%,and temperature was 30°C.3.The effects of three single factors(pH value,OD,and initial concentration of Cr³⁺)on the experimental results of Cr³⁺adsorption were investigated by the usage of response surface methodology?RSM?.The optimum adsorption conditions of the strain can be obtained through experimental analysis as follows:pH:6.25,OD:1.34,Cr³⁺:90.14 ppm,and the removal efficiency can reach 90%under the above conditions.4.The analysis of kinetic and adsorption isotherm equations shows that the adsorption process of Cr³⁺metal ions conforms to the pseudo-second-order kinetic equation,and both Langmuir and Freundlich adsorption isotherms can fit the experimental data well.The maximum bacterial adsorption capacity?qm?was 19.6 mg/g by the application of the Langmuir isotherm fitting.The current research on the control of heavy metal microbial pollution mainly focuses on the selection of strains that are resistant to heavy metals.This study not only screened strains resistant to heavy metal Cr?III?,but also studied the adsorption efficiency of Cr?III?and the adsorption capacity of the strains.It is beneficial to the comprehensive control of heavy metals contaminated by Cr?III?in the sea,and can provide references for the screening and utilization of other microorganisms used in environmental restoration.