| Magnetotctic bacteria are a kind of microorganism which can move parallel under magnetic field. They can synthesis of a special kind of organelle-magnetosome. Magnetosome is a nanometer scale crystal, enveloped with membrane vesicles. It has certain arrangement in the cell, which can lead the cell to migrate along magnetic field. Magnetosome has serious advantages such as:uniform size, large specific surface area, certain crystal shape, and good dipersion in the solution. The surface of magnetotactic bacteria is rich in active groups such as hydroxyl, amino and carboxylcan, which lead to adsorption on lead effectively. It can respond to the magnetic field, so it can be easily separation from waste water. It can reduce the secondary pollution, so it may be widely used in the treatment of lead ions.In this study, we used Magnetospirllum magneticum AMB-1from ATCC (700264) for researching. We changed the composition of culture and the conditions, to study the experimental factors have effections on the amount of bacteria and the production of magnetosome. The result showed that the addion of succinic adid of0.80g, sodium nitrate of0.12g, ferric quinate of2.0μmol, with appropriate amount of NaOH adjusting the initial solution pH to6.7, the fluid colume of70%(250mL conical flask), the vaccination volume of2%, cultivate at30℃for96h, the magnetotactic bacteria growth and the production of magnetosomes can reach the goal.Under such condition, we supposed that the types of reducing agents (Vitamin C, L-cysteine and thioglycolic acid) and their additions may have effections on the progress of magnetosome synthesis. The results showed that compared with other reductants, when the vitamin C of0.045g as reducing agents, we can obtain a large amount of bacteria, and the magnetosome arranged in one liner chains in bacteria with the significant magnetotactic characteristic.Using SAS software to optimize the factors, we carried on a Plackett-Burman experiment, the steepest ascent and the Box-Behnken experiment, respectively, using the magnetotactic bacteria growth and the production of magnetosomes as reponse values. The results showed that the addition amount of ferric quinate, the culture temperature and the pH have influences on the magnetotactic bacteria growth and the production of magnetosomes. The best experiment conditions were adding ferric quinate of2.7μmol, adjusting pH to6.8and incubating at32℃for96h. Under this condition, we can obtain a large amount of bacteria and higher magnetosome production.We used a large number of fermentation of magnetotactic bacteria as a bioadsobent for adsorption of lead ions, we studied many factors such as the initial pH, ionic strength, the concentration of lead ions, the amount of bacteria, the concentration of coexistence ions and the speed of mixture in turn which may have effections on the adsorption rate of lead ions. The result of optimizing was that pH5.3, adding magnetotactic bacteria of0.12g, mixing speed of170r·min-1, can obtain highest removal rate of lead ion.At the end of the paper, in order to understand the adsorption mechanism of lead ion, we studied the kinetics and thermodynamics, and combined with IR analysis. The result of dynamic experiment showed that the adsorption can complete within60min and the pseudo-first-order kinetic model fit the adsorption of lead ion by Magnetospirillum sp. AMB-1better than the pseudo-second-order model; the result of isothermal adsorption experiment found that Langmuir isothermal model can fit experimental data better; and the result of thermodynamic experimental suggested that the adsorption process was spontaneous, and the chemical adsorption was the main adsorption process; The IR analysis showed that the active groups such as carboxyl, amino, and hydroxyl on the surface of magnetotactic bacteria played an important role in adsorption process. |
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