報告書番号

U91009

タイトル（和文）

特殊環境に生育する水素細菌の分離とそのヒドロゲナーゼの性質

タイトル（英文）

ISOLATION OF HYDROGEN BACTERIA GROWING IN EXTREME ENVIRONMENTS AND PARTICAL CHARACTERIZATION OF HYDROGENASES

概要 （図表や脚注は「報告書全文」に掲載しております）

ヒドロゲナーゼは様々な工学的応用の可能性が考えられているが，酸素などに対して不安定なため，応用研究は進んでいない。本研究では高温，酸性などの特殊な環境で生育できる水素細菌を自然界より分離しその菌のヒドロゲナーゼの安定性を調べ，安定なヒドロゲナーゼを持つ水素細菌を選抜した。未精製ヒドロゲナーゼの安定性を調べたところ温泉湧出口の高温酸性試料から分離した６０℃，ｐＨ３で生育できる好酸高温菌２株，および３０℃，ｐＨ３で生育できる好酸中温菌１株のヒドロゲナーゼが高い安定性を有した。酸素を除去した酸素反応条件で７３時間保温したとき，好酸高温菌のビドロゲナーゼは２株とも活性がほとんど低下しなかった。また，大気条件下でも，好酸高温菌および好酸中温菌のヒドロゲナーゼは７３時間後７０％以上の活性を維持した

概要 （英文）

HYDROGENASE IS A MICROBIAL ENZYME THAT CATALYZES REVERSIBLE OXIDATION OF THE HYDROGEN MOLECULE. THERE HAS BEEN CONSIDERABLE INTERESTS IN ITS APPLICATION AS AN ALTERNATIVE TO EXPENSIVE PLATINUM CATALYSTS. HOWEVER,BECAUSE OF THE INSTABILITY OF HYDROGENASE,APPLICATION STUDIES HAVE NOT PROGRESSED. THE AUTHOR ISOLATED HYDROGEN BACTERIA THAT GROW IN EXTREME ENVIRONMENTS(HIGH TEMPERATURE,HIGH OR LOW PH,HIGH OXYGEN CONCENTRATION,AND HIGH NACL CONCENTRATION)FROM VARIOUS SOILAND WATER SAMPLES. THREE ACIDOPHILIC,HYDROGEN BACTERIA(THERMOPHILE 3H-1,3H-3;MESOPHILE 3L-2)SHOWED GOOD GROWTH AND CONTAINED STABLE HYDROGENASES. THE STABILITY OF THE HYDROGENASES WAS ASSAYED BY MONITORING THE DECREASE IN HYDROGENASE ACTIVITY IN CELL-FREE EXTRACTS DURING INCUBATION.A CELL-FREE HYDROGENASE EXTRACT OF ALCALIGENES EUTROPHUS WAS USED AS AREFERENCE BECAUSE IT IS REGARDED AS RELATIVELY STABLE. WHEN THE HYDROGENASES WERE INCUBATED ANAEROBICALLY IN ENZYME REACTION CONDITIONS,THE ACTIVITY OF 3L-2 AND A.EUTROPHUS DECREASED TO HALF THE ORIGINAL ACTIVITYIN 73 HOURS. IN THE SAME CONDITIONS,THE HYDROGENASE ACTIVITY OF 3H-1 AND 3H-3 DECREASED SLIGHTLY. IN AEROBIC CONDITIONS,70% OF THE ACTIVITY OF 3H-1,3H-3 AND 3L-2 REMAINED AT 73 HOURS,WHILE THE ACTIVITY OF A.EUTROPHUS DISAPPEARED WITHIN 27 HOURS. WHEN THE HYDROGENASES WERE INCUBATED IN BUFFERS OF VARIANS PH,THE ACTIVITY OF A.EUTROPHUS DISAPPEARED BELOW PH5. ON THE OTHER HAND,THE ACTIVITY OF 3H-1,3H-3 AND 3L-2 WERE STABLE UNDER THE SAME CONDITIONS. THE HYDROGENASE ACTIVITIES OF THESE ACIDOPHILIC BACTERIA WAS MAINTAINED AFTER INCUBATION AT 80DEGREE FOR 30 MINUTES INDICATING THAT THEY ALSO HAVE HIGHER THERMOSTABILITY THAN A.EUTROPHUS HYDROGENASE.

報告者

キーワード