The Screening,Mutagenesis And Immobilization On Heavy Metal Adsorptive Bacterium

Heavy metal wastewater is one of the most serious factors to environment and human body. So biosorption is applied in treatment of heavy metal wastewater. Compared with the traditional methods of treating heavy metal wastewater, the biosorption is suitable for treatment of the wastewater with low concentration of heavy metal ions without secondary pollution.Four strains with high resistance to nickel, zinc, copper and chromium, were isolated from Fen River. The resistance of B8 to nickel and zinc reached 9.68mmol/L and 8.80mmol/L, and the resistance of B14 to copper and chromium(VI) reached 5.86mmol/L and 3.40mmol/L. The tests demonstrated that the environmental suitability of B8 and B14 were excellent. And the growth curves indicated that the lag and exponential phase were similar. While the stationary phase of B8 was longer than that of B14. So the strain B8 was selected to further study.Ultraviolet, microwave and plasma were used to mutate B8. The results showed that the resistance to zinc and chromium(Ⅵ) of mutants by ultraviolet and plasma reached 10.94mmol/L and 14.67mmol/L, and the positive mutation frequency of which was much higher than that of mutants by microwave. Four mutants, the adsorbability on nickel of which was much stronger than that of wild strain B8, were screened among mutants by plasma. The adsorption on nickel ions of the mutant Nil2 reached 136.7 mg/g (dry bacteria), which was 11.7% higher than that of wild strain B8, and the mutant Nil2 inherited stable. The result of 16S rDNA sequence analysis indicated that the mutant Ni12 was Pseudomonas cedrina. The method of mutagenesis by plasma was high efficiency and promising in future.Biofilm was cultured with porous ceramics as carrier, and bacteria B8 mutant Ni12 as seed. The results showed that the mature period of biofilm was about 23 d. The nickel-adsorption tests indicated that the adsorption on nickel ions of porous ceramics was much lower than that of microbe. And the adsorption balance rates of the mixture with B8 and the mixture with Ni12 were 77.7% and 86.5%. So the mutant Ni12 was a kind of bacteria which appropriate to treat nickel ions.