| Soil is an important part of the ecosystem,but currently facing various threats,among which soil pollution is the most serious.The bioremediation has been widely used in soil pollution control,because it has the character of the low cost,the good treatment effect and no secondary pollution,in which the screening of excellent strains is the key link of the management.The microbes that can be used for heavy metal accumulation are limited,and the effect is still to be improved.In view of the problems of Bioremediation techniques for soil pollution,this study was based on screening of lead tolerance strains,and exploring its growth characteristics and rules,and finding the best adsorption conditions.The adsorption kinetics and adsorption isothermal model were established,and the adsorption behavior was analyzed by adsorption and desorption experiments.We studied the intrinsic mechanism of strain about lead adsorption by transmission electron microscopy and infrared spectroscopy to study the adsorption mechanism of heavy metal lead.The results of the specific experiments study were as follows:?1?There are 23 strains of lead resistant bacteria isolated from contaminated soil samples from Taiyuan City,Shanxi Province by the using selective media,and step by step domestication,finally 5 strains with lead tolerance as high as 1000 mg·L-1 were obtained and one of them was a fungus;The adsorption effect of 5 strains was preliminarily detected by flame atomic spectrophotometer.Finally,strain GDYX03 with the best adsorption effect was taken as the research object,whose the adsorption rate and capacity reached 61.863%and 7.879 mg·g-1,respectively.The strain GDYX03 was identified as Enterobacter ludwigii by phenotypic analysis,physiological and biochemical analysis,Biolog identification method and16SrDNA gene amplification and sequencing,and the strains with lead tolerance as high as 2000 mg·g-1 were obtained.?2?UV spectrophotometer was used to measure the growth of strains in different growth stages,and the growth curve was drawn to determine the best time that is 16 hours when study on the effects of strain on growth factors at this time.The optimum culture conditions of the strain were found at pH of 6.0 with inoculation quantity of 10%,potato glucose medium,and the optimal medium of 10 mL/50 mL at 30?.?3?The adsorption effect of strain GDYX03 on Pb2+was determined by flame atomic absorption spectrophotometer.The results showed that the adsorption effect of living cells when the nutrient is not available is better than that of the growing cells.And the optimum conditions for maximum biosorption were found at pH of 5 to 6 with inoculation quantity of 5 g·L-1,what needs to be cultured for 72 h,initial Pb2+concentration of 100 mg·L-1,and contact time of 30 minutes at 30?.Under the optimal conditions,the adsorption rate and capacity reached 98.852%and 19.73 mg·g-1,respectively.The adsorption process of the strain follows pseudo second order rate kinetics and Langmuir adsorption isotherm models with R2 reached 0.999 and 0.996,respectively.Transmission electron microscope?TEM?and Fourier Transform Infra Red?FTIR?results revealed that the biosorption process mainly happens on the surface of GDYX03.?4?The results of indoor germination test showed that cole and maize seeds treated by GDYX03 ferment liquid germinated normal,and the germination and growth status of the seeds treated by lead solution and GDYX03 together were obviously better than that of the seeds treated by lead solution alone.The addition of bacterial agent can reduce the toxic effect of lead ion on seed germination,and promote the growth and development of seeds,which provides a scientific basis for the outdoor application of the strain GDYX03 in remediation of lead-contaminated soil.The screened Enterobacter GDYX03 had a good adsorption effect on Pb2+,and could be used as a good bioremediation agent to be developed,which provided a good indigenous strain resource for the treatment of heavy metal pollution in local soil. |
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