Effects of temperature, photosynthetic photon flux density, photoperiod and O2 and CO2 concentrations on growth rates of the symbiotic dinoflagellate, Amphidinium sp.

Abstract

Symbiotic dinoflagellates of the species Amphidi-nium are expected to be pharmaceutically useful microalgae because they produce antitumor macrolides. A microalgae production system with a large number of cells at a high density has been developed for the efficient production of macrolide compounds. In the present study, the effects of culture conditions on the cellular growth rate of dinoflagel-lates were investigated to determine the optimum culture conditions for obtaining high yields of microalgae. Amphidi-nium species was cultured under conditions with six temperature levels (21-35°C), six levels of photosynthetic photon flux density (15-70 μmol photons m −2 s −1), three levels of CO 2 concentration (0.02-0.1%), and three levels of O 2 concentration (0.2-21%). The number of cells cultured in a certain volume of solution was monitored microscopically and the cellular growth rate was expressed as the specific growth rate. The maximum specific growth rate was 0.022 h −1 at a temperature of 26°C and O 2 concentration of 5%, and the specific growth rate was saturated at a CO 2 concentration of 0.05%, a photosynthetic photon flux density of 35 μmol photons m −2 s −1 and a photoperiod of 12 h day −1 upon increasing each environmental parameter. The results demonstrate that Amphidinium species can multiply efficiently under conditions of relatively low light intensity and low O 2 concentration.