Study On Microbe Screening And Breeding For Uranium And Interaction

In recent years, microbial remediation has been used as a focus study of repair uranium pollution. In order to invstigate the efficient microbes combination to U(Ⅵ) and the interaction role mechanism, the influence of microbial culture media on the determination of U(Ⅵ) was surveyed. The culture media which has no influence to the measurement of U(Ⅵ) was screened. Spectrophotometric method to detect U(Ⅵ) and U(IV) in medium was established, with chemical minusing method. High resistance microbes and microbial combination to U(Ⅵ) were screened out. The cultural condition of effective microbial combination was obtained by orthogonal experiment. Next, through the addition of small molecule, its effects on the removal effect of microbial to U(Ⅵ) were investigated. Finally, the interaction mechanism between microbes and U(Ⅵ) were explored by fourier transform infrared spectroscopy(FTIR) and scanning electron microscopy-X-ray energy dispersive analysis(SEM-EDX). The main results were as follows:(1) The stability study of uranium in microbial culture media. The optimal preparation parameters of U(IV) which contain 10.0 mg/L U(Ⅵ), 12.0 g/L zinc granule, the reaction time of 180 min, are obtained by zinc grain reduction method. The formation rate of U(IV) can reach 95%.When the oscillation time at 48 h, the influence rate of NA, LB culture medium to U(Ⅵ) can reach 47.9% and 37.3%. While, the influence rate of TGY medium to U(Ⅵ) and U(IV) are only 5.6% and 8.6%. The influence rate of peptone and beef extract to U(Ⅵ) can up to 33.5% and 19.7% in single component. But, the influence rate of tryptone, glucose, to U(Ⅵ) are 2.8%, 2.7%. The influence of NA and LB culture medium to U(Ⅵ) measurement is further confirmed, While TGY medium has no impact to U(Ⅵ) measurement.(2) The establishment of U(Ⅵ) and U(IV) measurement method in TGY medium. U(IV) is obtained through total uranium minus U(Ⅵ) by minusing method. The measurement method in TGY medium is established combining with azo arsine(Ⅲ) spectrophotometry of U(Ⅵ). Finally, the precision and accuracy analysis of the method, obtain that the measurement linear range of U(Ⅵ) within 0.0-20.0 mg/L, the lower limit can be up to 0.05 mg/L, the recovery rate is 96%, RSD = 1.7%, the error is-4%.(3) Screening of the resistance microorganisms to U(Ⅵ). Six kinds of resistance strains are obtained, which are XJ1, XJ2, Kocuria rosea, Deinococcus radiodurans, Citrobacter freundii and Bacillus cereus. Under the condition of cultivation, the removal rate of three kinds of microbes to U(Ⅵ) is surveyed. Deinococcus radiodurans, Citrobacter freundii and Bacillus cereus to U(Ⅵ) have higher removal rate, reached 80.4%, 84.8% and 82.3%, respectively.(4) The building of microbial combination to the removal of U(Ⅵ) and the optimization culture conditions. Bacillus cereus-Citrobacter freundii and Citrobacter freundii-Deinococcus radiodurans combinations are established to U(Ⅵ) through tolerance comparison of single strain and strain combination. To removal rate of U(Ⅵ) as the index, the optimal culture conditions of two kinds of combinations are received by orthogonal experiment. The optimal culture conditions of Bacillus cereusCitrobacter freundii contain p H value 7.0, temperature 35.0 ℃, the initial concentration of 10.0 mg/L U(Ⅵ). The optimal culture conditions of Citrobacter freundii- Deinococcus radiodurans contain p H value 6.0, temperature 30.0 ℃, the initial concentration of 10.0 mg/L U(Ⅵ).(5) The influence of small molecules to the U(Ⅵ) removal of microbe. A significant promoting role of ethanol, sodium acetate, sodium pyruvate and glucose to removal process of Citrobacter freundii, Bacillus cereus, Deinococcus radiodurans are found. The most significant removal effect to U(Ⅵ) is 5.0-15.0 m M ethanol. When it is joined the cultivation system, U(Ⅵ) can be completely removed by three strains. But, sodium citrate has serious inhibition process to the removal of U(Ⅵ) for three strains.(6) The FTIR and SEM-EDX characterization of microbe to the removal of U(Ⅵ). Results show that the removal mechanisms of Citrobacter freundii, Bacillus cereus, Deinococcus radiodurans to U(Ⅵ) are different, which contain complexation role of-OH,-C=O,-NH2,-PO43- to U(Ⅵ), ion exchange role of Na+、Mg2+、Ca2+ to UO22+, microbial mineralization.In conclusion, U(Ⅵ) and U(Ⅵ) of biological samples can be determined by spectrophotometric method of U(Ⅵ) and U(Ⅵ). Two microbial combinations of Bacillus cereus-Citrobacter freundii and Citrobacter freundii-Deinococcus radiodurans to U(Ⅵ) are screened. Ethanol, sodium acetate, sodium pyruvate, glucose can promote removal effect of microbe to U(Ⅵ). The removal mechanism of microbe to U(Ⅵ) include interaction between part groups and U(Ⅵ), ion exchange, microbial mineralization.