The Development And Application Of Magnetic Bacteria Separator

The magnetosome is an ideal kind of bio-nano-magnetic material. Magnetotactic bacteria could migrate along the magnetic field lines, which was due to that they could synthesize intra-cellular magnetosomes. So the magnetotactic bacteria could be separated easily by magnetic separation. The research in this group discovered the fact that Acidithiobacillus ferrooxidans could synthesize intra-cellular magnetic particles. But the magnetotaxis of Acidithiobacillus ferrooxidans was so weak that strong magnetic cells could hardly be separated from cells suspension. In this paper we researched the magnetic separation of magnetic bacteria. Based on the magnetic separation theory we designed and developed a kind of magnetic bacteria separator. As the sample Acidithiobacillus ferrooxidans was separated by this magnetic separator, and the optimal operation condition was studied. A strain of strong magnetic Acidithiobacillus ferrooxidans was isolated by magnetic separation, and the culture condition of it was researched including the influence of magnetic field and optimal condition of maximum culture density. In addition, magnetic Acidithiobacillus ferrooxidans could be batch cultured in the laboratory first time by fed-batch fermentation.We developed a kind of magnetic bacteria separator, which could create high gradient magnetic field. Acidithiobacillus ferrooxidans was investigated as an example. Strong magnetic and weak magnetic cells were separated and collected. On average, the number of the magnetic particles presented in the strong magnetic cells was more than that of the weak magnetic cells.84.21% of the strong magnetic cells contained 4-10 magnetic particles. By comparison only 65.79% of the weak magnetic cells contained 1-3 magnetic particles. Moreover, semisolid-plate magnetophoresis showed that the magnetotaxis of strong magnetic cells was stronger than the weak magnetic cells. These results suggest that the magnetic separator could be used to isolate the magnetic bacteria. When the magnetic flux density of outlet a and b reached 1220mT and 900mT and the suspension flow with the cells density of 108 ml-1 was controlled by a applying a rate of 884mL/h, the separation efficiency achieved maximum in the orthogonal experiments.We separated Acidithiobacillus ferrooxidans using the magnetic separator and optimized the culture conditions of Acidithiobacillus ferrooxidans by orthogonal experiments. We found that Acidithiobacillus ferrooxidans grew best at initial pH value of 2.0,35℃and 150rpm when added 44.7g/L FeSO4 into 200mL cultured medium.We batch cultured Acidithiobacillus ferrooxidans in the laboratory by fed-batch fermentation. In the shake-flask fermentation, the final volume of liquid was 2 L. After 40 h in the fermentation Fe2+(5%) was added in the fermentation liquid. The max cell density could reach 2.33×107 mL-1. Compared with control experiments it increased by 60.69%. At the same condition, the completion 9K culture medium was added in the fermentation liquid. The max cell density could reach 2.47×107 mL-1. Compared with control experiments it increased by 70.34%. And atom force microscopy and magnetic force microscopy showed that cells in the fermentation were magnetic.