A comparative study on three quantitating methods of microalgal biomass

Abstract

<em>Nannochloropsis oculata, Nannochloropsis salina</em>, <em>Nannochloropsis oceanica</em>, <em>Phaeodactylum tricornutum</em> and <em>Cylindrotheca fusiformis</em> were cultured in liquid <em>f</em>/2 medium with aeration till the end of exponential growth phase and serially diluted into eight cell suspensions, and cell concentration, optical density and dry weight in each suspension were determined. The cell density was counted on a hemocytometer, while optical density was measured in the spectrophotometer at 750 nm and dry weight was assayed after a lyophilization procedure. We found significant linear correlations between cell density, optical density and dry weight. When the cell concentration was low, the correlation between optical density and cell density was stronger than that between dry weight and cell density. When the cell concentration was high, the dry weight method was more accurate than other two, thus being applicable to single and high quality measurement.