| Budget Amount *help |
¥3,680,000 (Direct Cost: ¥3,500,000、Indirect Cost: ¥180,000)
Fiscal Year 2007: ¥780,000 (Direct Cost: ¥600,000、Indirect Cost: ¥180,000)
Fiscal Year 2006: ¥2,900,000 (Direct Cost: ¥2,900,000)
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| Research Abstract |
Dissolution experiments of kaolinite in bacterial systems containing bacteria (Pseudomonas fluorescens)were carried out to evaluate the effects of bacteria on dissolution rates and to elucidate the reaction mechanisms. Similar dissolution experiments using proteinic systems containing ovalbumin (OVA) were also performed to confirm the effects of protein on the kaolinite dissolution rates. The dissolution experiments in bacterial systems were performed using batch reactors containing 0.2 g of kaolinite and 100 ml of 10 mM NaCl solution with 10^5 to 10^9 cells/ml of bacteria at 25℃ for up to 30 days. The dissolution experiments of proteinic systems were also conducted using similar methods, however, 0.05, 0.1, 0.2, 0.5, and 1.0 mg/ml of OVA were used instead of bacteria. The results for the bacterial systems indicated that the dissolution rate of kaolinite increased by 1.6-, 2.6-, 3.4-, 4.6-, and 10.4-fold progressively with increasing bacterial concentrations of 10^5, 10^6, 10^7, 10^8 a
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nd 10^9 cells/ml, respectively, relative to the bacteria-free control. The concentrations of dissolved Al ions also increased up to 50 times compared to the equilibrium concentrations of Al-hydroxides such as gibbsite with increasing bacterial concentrations. The chemical analyses of organic molecules in the solutions of bacterial systems revealed that significant amounts of proteins were released from bacterial cells along with lesser amounts of polysaccharides and organic acids. Thus, it can be concluded that these extracellular organic molecules consisting mainly of proteins contribute to the enhancement of the rate of kaolinite dissolution by interacting with the kaolinite surfaces. They also lead to an increase in the dissolved Al concentrations by undergoing complexation with the dissolved Al ions. The dissolution experiments in the proteinic systems containing OVA exhibited greater enhancement in kaolinite dissolution of 1.5-, 2.3-, 3.1-, 14.2-, and 16.2-fold with increasing OVA concentrations. This result strongly suggests that the dissolution of kaolinite in bacterial systems may be enhanced by its interaction with the extracellular proteins released from the bacterial cells by the mechanism of ligand-promoted dissolution. Less
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