IN-VIVO CHARACTERIZATION OF ESTERASE-ACTIVITY IN CALOTHRIX PCC-7601, HASLEA-OSTREARIA AND PROROCENTRUM-MICANS

A fluorometric method for rapid measurement and characterization of nonspecific esterase activity was tested on several microalgae: Calothrix PCC 7601 (Cyanophyceae), Haslea ostrearia Simonsen (diatom) and Prorocentrum micans Ehrenberg (dinoflagellate). Km (in mumol L-1) and Vm (in fluorescence units) were respectively 7.5 and 131 for Calothrix, 6.1 and 32.1 for H. ostrearia and 4.7 and 19.4 for P. micans. A standard measurement protocol based on enzymatic characterization showed (1) that photoperiod-dependent esterase activity was minimal at the end of the dark phase and maximal after 8 hours of light phase during a 12 h: 12BAR h photoperiod and (2) that there was a relation between esterase activity and temperature, irradiance, salinity and growth phase. Thus, fluorometric measurement of esterase activity seems to be a good indicator of the metabolic activity of microalgae.