ユーグレナの光合成生育に与える光質とCO_2濃度の影響 [in Japanese] Effect of Light Quality and CO_2 Concentration on Photosynthetic Growth of Euglena gracilis [in Japanese]
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World population is rapidly increasing, while the current food production cannot meet the need of the exponentially growing population. Accordingly, we are planning to develop a new food resource system by photosynthetically culturing a microalga <I>Euglena gracilis</I>. Moreover, it is aimed to reduce the excessive CO<SUB>2</SUB> in the atmosphere by making use of culturing <I>Euglena</I>. As a fundamental study on this new food resource system, this paper investigated the effect of light quality and CO<SUB>2</SUB> concentration on photosynthetic growth of <I>Euglena</I>. Light emitting diodes (LEDs) were used as red and blue light sources to examine the effect of light quality. On the air condition (with 0.04 % CO<SUB>2</SUB>), red and blue (PPF ratio = 9:1) LEDs showed the best effect on the growth of <I>Euglena</I>, while blue LEDs the worst. On the condition of high CO<SUB>2</SUB> (with 10 % CO<SUB>2</SUB>), no significant difference was found in the growth of <I>Euglena</I> among all of the light quality treatments. Chlorophyll content and Chlorophyll a/b ratio may account for these results. On the air condition with blue LEDs, energy level of photons is higher than those in other light quality treatments. The synthetic amount of protein of photosystem II (PS II) is more than the destructive one, and consequently the amount of protein in Chlorophyll b increased. Thus Chlorophyll a/b ratio decreased with the increase of Chlorophyll b. As a result, photosynthetic growth of <I>Euglena</I> decreased due to the decrease of photosynthetic activity. In contrast, on the condition of high CO<SUB>2</SUB>, since <I>Euglena</I> does not have the mechanism of CO<SUB>2</SUB> concentration, much CO<SUB>2</SUB> available for reduction presented in cells. Thus by increasing the CO<SUB>2</SUB> reduction and photosynthetic activity, <I>Euglena</I> in high CO<SUB>2</SUB> grew better than in the air.
Eco-Engineering 19(1), 27-32, 2007-01-31
The Society of Eco-Engineering