SATO Kazuhisa Tohoku Univ.,Faculty of Engineering,Research Associate, 工学部, 助手 (30215769)
ZHENG Shuang Ning Tohoku Univ.,Faculty of Engineering,Research Associate, 工学部, 助手 (60227486)
YONEMOTO Toshikuni Tohoku Univ.,Faculty of Engineering,Associate Professor, 工学部, 助教授 (40125688)
|Budget Amount *help
¥4,300,000 (Direct Cost : ¥4,300,000)
Fiscal Year 1992 : ¥800,000 (Direct Cost : ¥800,000)
Fiscal Year 1991 : ¥3,500,000 (Direct Cost : ¥3,500,000)
Recently, photoculture of microalgae which have a high photosynthetic ability has been paid atcention for one of the means of utilizing carbon dioxide discharged into the atmosphere. In order to obtain the basic knowledge of photoculture of microalgae in the photobioreactor using sun light, batch culture experiments of Chlorella using electroluminescent light, flat backlight and fluorescent light were carried out.
We used the reactor made of Pyrex-glass designed by ourselves. Pigment concentrations were represented by absorbance for respective pigments, which were measured by use of spectrophotometer with integral sphere.
To estimate biomass amount, we measured both absorbances at 680 nm for chlorophyll a and at 780 nm for turbidity of cell suspension, and then obtained the relations between these absorbances and dry weight, respectively. It was indicated turbidity is a more adequate index of dry weight than chlorophyll a.
Photocultures at various light intensity from 1,000 to 11,000lux were carried out and the effect of light intensity on growth rate and pigment composition of Chlorella was investigated. It was shown that the maximum absorbance for turbidity is held constant at any light intensities. On the other hand, chlorophyll a decreased with increase of light intensity. Furthermore, time courses of chlorophyll a, turbidity and cell number indicated that the increase of chlorophyll a and turbidity can represent the progress of cell division and whole cell growth, respectively.
When light intensity was high, because of algae cell adaptation to high light, the intracellular amount of photosynthetic pigments such as chlorophyll a, b and carotenoids decreased, and the ratio of chlorophyll b and carotenoids to chlorophyll a increased. As a result, light adaptation of Chlorella is supposed to be mainly carried out by changing the content of chlorophyll a.