| In recent years,because of the more serious heavy metal pollution,how to control heavy metal pollution quickly and effectively has become a hot issue in the current research,the application of yeast with potential beneficial characteristics to adsorb heavy metals to solve this problem provides a new way of thinking.In this paper,the Metschnikowia chrysoperlae QK-1-5,Metschnikowia chrysoperlae QE-1-1-2,abnormal Wickerhamomyces anomalus QF-1-1,Wickerha,momyces anomalus QI-1-7 of high adsorption Pb2+were selected by Acid resistance test,biliary salt test,simulated artificial gastrointestinal environment test and antioxidant test in the early stage of this experiment.After comprehensive comparison,the selection of Metschnikowia chrysoperlae QK-1-5 for subsequent adsorption characteristics and adsorption mechanism was studied.The adsorption capacity and adsorption characteristics of Metschnikowia chrysoperlae QK-1-5 were preliminarily investigated by high-throughput adsorption method,and the adsorption capacity of the strain was further studied and optimized by means of response surface method,and the adsorption of yeast was carried out by desorption test,chemical reagent treatment test,functional groups masking test,scanning electron microscope(SEM)and other tests Pb2+The mechanism is analyzed in depth,and the adsorption process is fitted by isothermal adsorption model and adsorption kinetics.The research results are as follows:4 strains of yeast can be better resistant to acid,alkali environment and bile salt stress,after simulating artificial gastrointestinal fluid treatment continuous 8h,found that strain QK-1-5,QF-1-1,QE-1-1-2 on the simulated artificial gastrointestinal fluid has a strong tolerance.After removing DPPH free radicals,removing HO free radicals and removing superoxide anions,it was found that strain QK-1-5,QF-1-1 and QE-1-1-2 had certain antioxidant ability,and there were significant differences between bacterial suspension and non-cell extracts(p<0.05).The adsorption capacity of strain QK-1-5 was studied by taking pH value,adsorption temperature,adsorption time,bacterial concentration and initial Pb2+concentration as the influencing factors.The pH value has a great influence on the adsorption ability,and with the increase of pH value,the adsorption capacity also increases,and with the increasing concentration of bacteria,the adsorption capacity of strain QK-1-5 increases,and the equilibrium is reached at 15 g/L,and the adsorption capacity reaches the maximum when the initial concentration of Pb2+is 100 mg/L.With the increase of initial concentration of Pb2+,the adsorption rate decreased greatly.With the increase of adsorption time,the adsorption ability of strain QK-1-5 to Pb2+showed an upward trend,reaching equilibrium at 150min,the optimum adsorption temperature of strain QK-1-5 was 30?,and the adsorption capacity of strain decreased with the increase of temperature.Through the response surface test,it was found that the concentration of bacteria and the initial concentration of Pb2+ interacted,and after optimization,the optimum adsorption conditions of strain QK-1-5 were bacterial concentration 14.78 g/L,adsorption time 150.15 min,Pb2+ concentration 118.52 mg/L,pH value 6.0,adsorption temperature 30?,Under this condition,the maximum adsorption amount 5.89 mg/g can be achieved.The process of strain QK-1-5 adsorption Pb2+ can be explained by Langmuir equation,and conforms to the maximum single-molecule layer adsorption theory of quasi-two adsorption kinetics.The adsorption mechanism of strain QK-1-5 was explored by desorption test,group masking test,chemical reagent treatment test and scanning electron microscope.Through the desorption test,it is found that different eluting fluids have different degree of elution ability to strain QK-1-5,and it is found that carboxyl group,amino and phosphoric acid groups play an important role in the adsorption process through group masking test,and the adsorption capacity of strain QK-1-5 has changed with different amplitude after chemical reagent treatment.Scanning electron microscopy(SEM)observed that Pb2+can poison cells,seriously damage the shape of the bacteria,the surface of the cell has granular sediment,presumably for the adsorption process of the Pb2+ attached to the cell surface.The results of this study can provide data support for the development of new heavy metal adsorbent,and provide a preliminary theoretical basis for the mechanism of yeast adsorption of heavy metals. |
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