Characterization of Chlorella cell cultures in batch and continuous operations under a photoautotrophic condition

Abstract

In a microalgal culture under illuminated conditions, the production rate of cells depends on the distribution of light intensity and growth rate of cells. The relationship between light transmittance through culture liquid and cell concentration was estimated from experimental data using a green alga, Chlorella sp. UK001. In batch cultures of this alga, the optimum conditions for the growth were temperature of 30°C and pH of 5.7. Under these conditions, the value of specific growth rate of the alga increased with the increase in incident light intensity (I0) up to 130 W m-2, and it decreased when I0 was over 130 W m-2. Continuous cultures of the alga in a rectangular reactor were performed at I0 = 55.8 and 71.4 W m-2. The dilution rates maximizing the production rate of cells existed for the respective values of I0. The production rates of cells in these cultures were calculated considering the distribution of light intensity in the reactor. The calculated results could successfully describe the experimental data at different dilution rates, and when I0 = 55.8 and 71.4 W m-2, the production rates of cells indicated maxima at dilution rates of 0.0218 and 0.0220 h-1, respectively.