| Co-Investigator(Kenkyū-buntansha) |
TAMURA Yoshitaka Morinaga, Central Research Center, Assistant Research Manager, 中央研究所, 主任研究員
NAGANO Tetsuo Tokyo University, Departmenet of Pharmacology, Professor, 薬学部, 教授 (20111552)
YANO Shigenobu Nara Women's University, Department of Chemistry, Professor, 理学部, 教授 (60011186)
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| Research Abstract |
Methylosinus trichosporium OB3b (OB3b) is a methanotroph that utilizes methane as their sole source of carbon and energy. The initial transformation involves the conversion of methane into methanol by methane monooxygenase (MMO). In this study, methanol accumulation by selecting the culture and the reaction conditions was studied.
The effect of copper concentration in medium on the MMO activity was investigated. When OB3b was grown on the medium containing high copper ion, the MMO activity was high, however, the specific growth rate was low. The optimimum concentration of copper in the medium was 1.25 muM.
To optimize the methanol production by OB3b, the effects of cell density, sodium formate concentration, temperature, phosphate buffer concentration, and cyclopropanol treatment condition, on the reaction were studied. The cyclopropanol treatment was carried out with 9.7 mg of dry-cell cell suspension and 9.38 muM cyclopropanol in 2 ml of 6.25 mM phosphate buffer (pH 7.0) in a 10 ml sample bottle for 5 min at 20。C.By optimizing the reaction condition, the reaction continued for 100 h and the produced methanol was 152 mmol per g of dry-cell, which is 51-fold higher than that of the conventional condition. The MDH activity in the cells retained ca. 50% under this condition. However, when the MDH activity was completely inhibited by cyclopropanol, the produced methanol was not observed. So a part of the produced methanol may serve as the electron donor for methane oxidation in this methanol biosynthesis, the reaction may continue for over 100 h, so that the produced methanol increased.
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