報告書番号

U97025

タイトル（和文）

微生物によるＣＯ２固定６．螺旋状チューブラーリアクターを用いたクロレラの屋外培養における光合成生産性

タイトル（英文）

MICROBIAL CO2 FIXATION 6. -PHOTOSYNTHETIC PRODUCTION OF CHLORELLA SP. IN OUTDOOR CULTURE EXPERIMENT USING HELICAL TUBULAR BIOREACTOR

概要 （図表や脚注は「報告書全文」に掲載しております）

屋外設置型の螺旋状チューブラーリアクター（設置面積１．１ｍ２）におけるクロレラの生産性について検討した。日射量の増加に伴って生産性が高くなり，最も高い結果は，日間最大成長速度で１７．９ｇ乾物／設置面積ｍ２／日，光合成効率は４．１２％（ＰＡＲ）であった。春季や秋季には太陽光の照射によって速やかに培養液温が上昇し，適切なレベルに維持された。一方，夏季には適切な温度まで冷却する必要があり，温度制御によって良好な生産性が示された。クロレラの生産性は，これまでに行ってきた室内実験結果より２割程度低かった。リアクターの大型化に伴って培養液がスムーズに流れにくくなったことが原因と考えられた。このため，流動性を改善するのに，リアクターサイズの適正化について室内実験で検討した。生産性ならびに光合成効率も０．２５ｍ２タイプと同等かそれ以上であったことから，１ユニットの大きさとしてはこの程度が適切と考えられた。

概要 （英文）

TO MITIGATE GLOBAL WARMING, MICROALGAL CO2 FIXATION/CONVERSION TECHNOLOGIES HAVE BEEN INVESTIGATED. IN A PREVIOUS REPORT, WE DEVELOPED A LABORATORY-SCALE PHOTOBIOREACTOR, TO UTILIZE STACK GAS FROM A THERMAL POWER PLANT. IN ADDITION, IT IS NECESSARY TO DESIGN A BIOREACTOR FOR OUTDOOR CULTURE THAT CAN USE SOLAR RADIATION DIRECTLY. HELICAL TUBULAR BIOREACTORS FOR OUTDOOR CULTURE WERE CONSTRUCTED WITH A 1.1-SQUARE M INSTALLATION AREA AND THE PHOTOSYNTHETIC PRODUCTION OFCHLORELLA WAS INVESTIGATED FROM MAY TO NOVEMBER 1996. THE FOLLOWING RESULTS WERE OBTAINED: (1)PHOTOSYNTHETIC PRODUCTIVITY CORRESPONDED WITH SOLAR RADIATION; MAXIMUM GROWTH RATE WAS 17.9 DRY WEIGHT BIOMASS/SQUARE M INSTALLATION AREA/DAY, AND PHOTOSYNTHETIC EFFICIENCY WAS 4.12% (PAR).(2)SINCE THE ILLUMINATED AREA TO CULTURE VOLUME WAS HIGH, THE TEMPERATURE CHANGE RESPONSE OF THE CULTURE BROTH TO SOLAR RADIATION OR AMBIENT TEMPERATURE WAS FAST. IN SPRING OR AUTUMN, THE TEMPERATURE OF THE CULTURE BROTH INCREASED WITH SOLAR RADIATION AND WAS MAINTAINED AT A SUITABLE LEVEL. IN SUMMER, IT INCREASED BEYOND THE SUITABLE LEVEL, AND THE TEMPERATURE WAS REDUCED BY SPRAYING WATER ON THE PHOTOSTAGE. IT IS IMPORTANT TO DEVELOP A CHEAP AND EASY CULTURE BROTH TEMTERATURE CONTROL SYSTEM. ALTHOUGH THE PHOTOSYNTHETIC PRODUCTIVITY IN THIS RESEARCH WAS SIMILAROR A LITTLE HIGHER THAN THAT OF A CONVENTIONAL OPEN-TYPE REACTOR, IT WAS 20% LESS THAN THE PREVIOUS INDOOR EXPERIMENT. THIS WAS PROBABLY DUE TO THE SLOW FLOW OF THE CULTURE BROTH IN THE BIOREACTOR TUBING, BECAUSETHE OUTDOOR BIOREACTOR WAS FOUR TIMES BIGGAER THAN THE LABORATORY REACTOR TO INCREASE THE CO2 REMOVAL RATE. TO IMPROVE THE CULTURE BROTH FLOW, THE BIOREACTOR SIZE WAS EXAMINED. A BIOREACTOR WITH A 0.5-SQUARE M INSTALLATION AREA WAS CONSTRUCTED AND THE PHOTOSYNTHETIC PRODUCTION OF CHLORELLA UNDER LABORATORY CONDITIONS WAS EXAMINED. THE PHOTOSYNTHETIC EFFICIENCY WAS SIMILAR TO OR A LITTLE HIGHER THAN THE 0.25SQUARE M BIOREACTOR, INDICATING THAT THE 0.5SQUARE M S

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