報告書番号

U92052

タイトル（和文）

石炭の生物加工－６－鉄酸化細菌の黄鉄鉱への選択的吸着

タイトル（英文）

COOL BIOPROCESSING -6- SELECTIVE ADHESION OFIRON-OXIDIZING BACTERIUM TO PYRITE

概要 （図表や脚注は「報告書全文」に掲載しております）

鉄酸化細菌を用いた微生物浮遊選炭における遺伝的改良による脱硫効果の向上を目指し，鉄酸化細菌の黄鉄鉱への吸着について検討した。大腸菌が，物理的作用によってより疎水性の鉱物に吸着しやすい傾向を示したのに対し，鉄酸化細菌は，物理的作用による吸着傾向とは異なり黄鉄鉱や黄銅鉱に選択的に吸着する能力を持っていた。この選択的吸着は，黄鉄鉱や黄銅鉱中の還元状態の鉄と微生物との間の強い相互作用によるものと考えられた。以上より，鉄酸化細菌は，微生物浮遊選炭に適した微生物であり，また，この選択的吸着性は，石炭の脱流ばかりでなく，広く微生物自身を生物界面活性剤として使う新しい微生物利用法として適用できることを見い出した。

概要 （英文）

COAL COMBUSTION RELEASES SULFUR DIOXIDE INTOTHE ENVIRONMENT. MICROBIAL FLOTATION HAS BEEN PROPOSED AS A COST-EFFECTIVE DESULFURIZATION TECHNIQUE. WE HAVE REPORTED THAT BACTERIAL ADHESION TO PYRITE IS THE MOST IMPORTANT FACTOR IN DESULFURIZATION. HOWEVER,FOR IMPROVED DESULFURIZATION BY MICROBIAL FLOTATION,WE MUST UNDERSTAND ADHESION OF IRON-OXIDIZING BACTERIA TO PYRITE. THIS REPORT INVESTIGATED SELECTIVE ADHESION OF T. FERROOXIDANS TO PYRITE. E COLI WAS USED AS A CONTROL. T. FERROOXIDANS IS MORE HYDROPHILIC THAN E. COLI. E. COLI TENDS TO ADHERE TO HYDROPHOBIC ORES BY PHYSICAL INTERACTION BETWEEN THE BACTERIUM AND ORE. HOWEVER,T. FERROXIDANS ADHERES SELECTIVELY TO PYRITE AND CHALCOPYRITE BY A SPECIFIC INTERACTION. REVERSION ADHESION TO PYRITE ISOBSERVED WITH E. COLI WHILE IRREVERSIBLE ADHESION IS OBSERVED WITH T. FERROOXIDANS. FERROUS IONS INHIBITED ADHESION OF T. FERROOXIDANS TO PYRITE COMPETITIVELY. HOWEVER,FERRIC IONS HARDLY INHIBITED ADHESION. T. FERROOXIDANS TENDS TO ADHERE TO MORE HYDROPHILIC ORES BY PYSICAL INTERACTION WHEN SELECTIVE ADHESION IS BLOCKED COMPLETELY BY FERROUS IONS. THESE RESULTS SUGGEST THAT T. FERROOXIDANS CAN RECOGNIZE REDUCED IRON IN PYRITE AND CHALCOPYRITE AND PRODUCES THE SPECIFIC INTERACTION BETWEEN IRON AND THE OUTER MEMBRANE. MICROBIAL SELECTIVE ADHESION CHANGES THE SURFACE PROPERTIES OF PYRITE IN COAL. THUS,IF SELECTIVITY IS ENHANCED BY GENE TO MANIPULATION,DESULFURIZATION MIGHT IMPROVE. THE ADHESION AND CHANGED SURFACE PROPERTIES ARE SIMILAR TO THE EFFECT OF A CHEMICAL SURFACTANT,BUT THE BACTERIAL SURFACTANT IS SUPERIOR IN SELECTIVITY. IT WILL BE A NOVEL TECHNIQUE TO USE BACTERIA AS A BIOLOGICAL SURFACTANT FOR SEPARATION OF SPECIFIC SUBSTANCES.

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