Abstract
The green alga Chlorella contains a storage polysaccharide, starch, which consists of amylose and amylopectin. Effects of various environmental factors during the growth on the intercellular content and structure of starch were investigated. When high CO2 (3%)-grown cells were transferred to low CO2 ( 0.04%, air level ) condition, pyrenoid and pirenoid starch developed, and starch content and the ratio of amylose to amylopectin increased. The chain length distribution of amylopectin was also affected by CO2 concentration during the growth. After NH4+ addition or in the dark, starch content decreased and the rate of amylose to amylopectin increased. Furthermore, expression of granule-bound starch synthase (GBSS), which is considered to be responsible mainly for the amylose synthesis, was determined. The result suggests that GBSS expression is upregulated at the transcritional level in the low CO2-condition.
