報告書番号

U93041

タイトル（和文）

石炭の生物加工－８－２価鉄を用いた鉄酸化細菌の連続培養

タイトル（英文）

BIOPROCESSING OF COAL -8- CONTINUOUS CULTUREOF THIOBACILLUS FERROXIDANS ON FERROUS IRON AS ENERGY SOURCE

概要 （図表や脚注は「報告書全文」に掲載しております）

微生物浮遊選炭に使用するＴｈｉｏｂａｃｉｌｌｕｓｆｅｒｒｏｘｉｄａｎｓの２価鉄を用いた連続培養技術の確立のため、沈殿物生成のない培養条件を検討した。回分培養実験において、９Ｋ培地の初期ｐＨを１．５に下げることにより沈殿物の生成を抑制できるが、初期ｐＨが２．０の場合に比べ生育速度は遅く、最終菌体密度は半減した。培地中のカリウムを９Ｋ培地の１／２０とした改良培地を用い、沈殿物の生成量を少なく、かつ菌体の生育を９Ｋ培地と同等にすることができた。改良培地を用いた連続培養実験においてｐＨを１．６０－１．６５に制御した場合、ほぼ沈殿物の生成はなく、１カ月間以上の連続培養が可能となった。希釈率０．０２５－０．０２７ｈ＊＊１における培養槽中の菌体密度は１．７＊１０＊＊８個／ｍｌであり、菌体生産性は同容量の回分培養の約１．５倍であった。培養槽中に５％ＣＯ２混合空気を通気し、菌体密度を２．２＊１０＊＊８個

概要 （英文）

COAL IS AN ABUNDANT ENERGY RESOURCE WORLDWIDE. HOWEVER, ITS COMBUSTION PRODUCES SULFUR DIOXIDE WHICH CAUSES ACID DEPOSITION. MICROBIAL FLOTATION IS AN EFFECTIVE METHOD OF REMOVING SULFURFROM COAL BEFORE COMBUSTION. THIS METHOD HAS THE ADVANTAGE OF QUICK TREATMENT COMPARED WITH THE MICROBIAL LEACHING METHOD. ON THE OTHER HAND,MICROBIAL FLOTATION REQUIRES CONTINUOUS SUPPLY OF MICROORGANISMS INTO THE DESULFURIZATION SYSTEM. CONTINUOUS CULTURE IS KNOWN TO BE A USEFUL MEHTOD TO PRODUCE MICROORGANISMS AT HIGH PRODUCTIVITY. HOWEVER, IT IS DIFFICULT FOR THIOBACILLUS FERROOXIDANS TO BE CULTURED CONTINUOUSLY ON FERROUS IRON FOR A LONG TIME BECAUSE THE CULTURE EASILY FORMS PRECIPITATES. CULTURE CONDITIONS FACILITATING CONTINUOUS CULTURE OF THIOBACILLUS FERROOXIDANS WERE INVESTIGATED BY BATCH CULTURE. CONSIDERABLE PRECIPITATION OCCURS IN STANDARD CULTUE USING 9K MEDIUM AT INITIAL PH2.0. AT INITIAL PH1.5, PRECIPITATION WAS COMPLETELY SUPPRESSED, BUT THE MICROBIAL GROWTH SLOWED AND THE FINAL CELL DENSITY WAS ABOUT HALF THAT OF THE STANDARD CULTURE. A MODIFIED MEDIUM CONTAINING POTASSIUM OF 9K MEDIUM REDUCED PRECIPITATION AND MAINTAINED GOOD CELL GROWTH. ON THE BASIS OF BATCH CULTURE, CONTINUOUS CULTURE WAS INVESTIGATED. CONTROLLING THE PH OF THE MODIFIED MEDIUM IN THE RANGE OF 1.60-1.65 ACIVEVED CONTINUOUS CULTURE FOR 1 MONTH WITHOUT PRECIPITATES. AT A DILUTION RATE OF 0.025-0.027H**1, THE CELL DENSITY WAS 1.7X10**8/ML AND THE CELL PRODUCTIVITY WAS 1.5TIMES THAT BATCH CULTURE IN THE SAME VOLUME. CO2 ENRICHMENT AT A CONCENTRATION OF 5% INCREASED CELL DENSITY TO 2.2X10**8/ML IN CONTINUOUS CULTURE.

報告者

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