Growth Characteristics and Cellular Components of Chlorella regularis, Heterotrophic Fast Growing Strain

Abstract

A Chlorella strain with high growth rates under heterotrophic growth condition was isolated from a pond and identified as Chlorella regularis. The optimal temperature for growth was 36°C and the optimal pH 6.0~7.0. Glucose, galactose, acetic acid, ethanol, acetaldehyde and pyruvic acid may serve as the carbon source supporting the growth under both dark and light conditions. The specific growth rate μmax was; 0.3 hr−1 under autotrophic condition, 0.28 hr−1 under heterotrophic condition, and 0.45 hr−1 under mixotrophic condition. In the dark heterotrophic culture, the yield of the cells to glucose was 0.5~0.6, that to acetic acid 0.48, and that to ethanol 0.66. When dark heterotrophic cells were cultured under mixotrophic condition, the yield to glucose increased to 0.82, that to acetic acid to 0.85 and to ethanol to 0.91. The protein and chlorophyll contents of the cells in autotrophic culture were approximately, 60% and 4%, respectively. These contents of the cells in dark heterotrophic culture changed in accordance with the growth phase. The protein of the cells reached to, approximately, 60% and the chlorophyll to 2% in stationary phase of growth, although the cells were maintained even in the dark.