Isolation And Identification Of Pb～(2+) And Cd～(2+) Tolerance Microorganism And Screening Of Strains With High Efficient Pb～(2+) Absorbing Ability

Forty strains with ability of Pb²⁺ and Cd²⁺ tolerance, including 27 bacteria and 13 fungi strains, were isolated from lead and cadmium polluting soil. The physiological and biochemical aspects were studied. Bacteria was in genus of Planococcus, Anthrobacter, Staphyoccus, Flavobacterium, Morganella, Citrobacter, Pseudomonas, Xanthomonas, Alcaligenes, Achromobacter, Comamonas, Zoogloea, and fungi was identified in genus of Rhizopus, Fusarium, Penicillium , Saccharomyces, Trichoderma, Cephalosporiun and Mucor. Of these strains, three bacteria were screened and proved to be high effective strains to adsorb Pb²⁺, and their removal rate of Pb²⁺ reached more than 80%. The three strains were identified as Arthrobacter sp.(B02), Pseudomonas sp. (B19), and Alcaligenes sp. (B27), respectively.Strains B02, B19 and B27 were further used to study the properties of Pb²⁺biosorption, and the affecting factors, such as temperature, absorption time, culture time, culture media, pH were performed. The results indicated that the adsorption of Pb²⁺ was a non-temperature dependent process; and the absorption of Pb²⁺ was a very short and rapid process. The absorption capacity got to the highest value within 30 min. The results also indicated that the media components heavily affected the removal rate of Pb²⁺.The optimum media for strain B02 was mushroom juice medium. However, both B19 and B27 use beeves medium as optimum medium. The results suggested that the 3 day's culture cells had occupied the strongest capacity of adsorbing Pb²⁺. The biosorpting capacity rose with increasing pH value, with the optimum pH 6.0. The removal rate of Pb²⁺ by strain B02, B19 and B27 were 94.9%, 83.5% and 87.9% respectively. The content of biomass and initial concentration in solution aslo affected biosorption rate strongly.The result of orthogonal test suggested that medium affected removal rate of Pb²⁺ strongly.The optimum adsorption condition for strain B02 were the mushroom juice medium, pH6.0, 0.12g of biomass, and the concentration of 80mg Pb²⁺/L; while, those of strain B19 and B27 were beeves medium, pH 5.5, 80mg Pb²⁺/L and 0.12g of biomass.