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Treatment of Wastewater Containing Cr(Ⅵ) with Bacillus Thuringiensis

Author: SuXinHua
Tutor: HuangTianPei；GuanXiong
School: Fujian Agriculture and Forestry University
Course: Biochemistry and Molecular Biology
Keywords: Cr (VI) Mutant library mini-Tn10 Bacillus thuringiensis
CLC: X703
Type: Master's thesis
Year: 2011
Downloads: 30
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Abstract


With the development of the industrial wastewater containing chromium and chromium slag lot emissions into the environment, has caused serious environmental pollution, to contain chromium contamination governance imminent. Toxic Cr (VI) is reduced to the low toxicity of Cr (III) the biosorption to bacterial and recycling, is one of the most commonly used method of bio governance Cr (VI)-containing wastewater pollution. Bacillus thuringiensis (Bacillus thuringiensis, referred to as Bt) strains and genetic resources are very rich, non-pathogenic, the test measured this room saved 76 Bt wastewater containing Cr (VI) reducing power, which strains the BRC- HZM7 and BRC-XQ15 available within 24 h to 50 mg / L of chromium (VI) is less than 0.5 mg / L, reached wastewater discharge standards in China. This proves that the the Bt strain on wastewater containing Cr (VI) generally has a strong reducing capacity, the initial establishment of Bt strains that can be applied to the Cr (VI) pollution control repository. To further resolve the efficiency factors affect the reduction of Cr (VI), the test sequencing strains of Bt 407 Cry-as the carrier, inoculum size, pH, temperature, and other heavy metals and glucose to restore the conditions of the Cr (VI) to optimize. The results show that the optimum inoculum size reduction of Cr (VI) The strain of 1%, the optimal pH 9.0, the optimum temperature is 35 oC, metal ions Mn2 Mo2, Cu2, Ni2 and glucose for Cr (VI ) reduction of Zn2 and Co2 suppress the reduction of Cr (VI). Under optimal conditions, Bt 407 Cry-strains at 36 h when 50 mg / L Cr (VI) of less than 0.5 mg / L to wastewater discharge standards in China. Cr (VI) after optimization reducing amount of up to 9.25 times before optimization, greatly improve the reduction efficiency. Bt 407 Cry-as research vectors, combined with bioinformatics analysis and random transposon mutagenesis technique obtained with the Cr (VI) reduction / adsorption related genes, to further clarify the mechanism of of Bt governance chromium pollution lay the foundation. Bioinformatic analysis showed that Bt 407 Cry-containing chromium resistance of the gene chrA and reduction of Cr (VI)-related genes, the gene azoR with known chromium reduction the gene chrR highly homologous, which is Bt 407 Cry-efficient restore Cr (VI) to provide a theoretical basis. In addition, the random transposon mutation carrier pIC333 transformed Bt 407 Cry-, and build capacity for 1500 Bt 407 Cry-random transposon insertion mutant library, 9 Cr (VI) reduction / adsorption capacity with the wild-type strain has extremely significant forward to improve (p lt; 0.01) mutant, were named as: of Bt 407-Cr5, of Bt 407-Cr15 Bt407-Cr22 Bt407-Cr90 Bt407-Cr108, ??Bt407-Cr215 of Bt 407-Cr259, of Bt 407 -Cr279, Bt 407-Cr281. Total DNA extracted nine mutants and completely digested with HindIII, self-ligated, transformed into E. coli TG1 cells, extracting the plasmid of the transformant, the mini-Tn10 flanking sequence was amplified and sequenced, to determine the rotation of the nine mutants Transposon insertion sites binding protein gene are encoded transfer. Bt 407 Cry-9 mutant phenotype study showed that: The growth curve of the wild-type strain and mutant strain is not significant differences clear mutant Cr (VI) restore / adsorption ability very significantly increase with strain The growth activity change has nothing to do. It was found that the total chromium content of most of the mutants in the process remained unchanged, indicating that the reduction of Cr (VI) in the wastewater mechanism of reduction of Cr (VI) by Bt.

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CLC: > Environmental science, safety science > Processing and comprehensive utilization of waste > General issues > Wastewater treatment and utilization
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