Calibration Curves of Culture Density Assessed by Spectrophotometer for Three Microalgae (Nephroselmis sp., Amphidinium carterae and Phormidium sp.)

Abstract

This study concerns the finding of an effective operational equation relating the measured absorpbance (or O.D. - optical density) in a spectrophotometer of the suspended cells of microalgae to their cell density (c.d.) in culture in order to construct calibration curves for use in culture operations. The microalgae examined were the chlorophyte Nephroselmis sp., the dinophyte Amphidinium carterae and the filamentous cyanobacterium Phormidium sp. Wavelengths of 430 and 680 nm were selected that correspond to chlorophyll-a peaks of their absorption spectra were used and additionally 750 and 570 nm where absorbance was not peaked. From all equations extracted best fitness with strong predictive values were those of a logarithmic type: O.D.=0,9328*ln(c.d.)-14,108 (R2=0,9943) at 680 nm for Nephroselmis, a power equation: O.D.=0,0000009*(c.d.)0,9195 (R2=0,9936) at 680 nm for Amphidinium and a polynomial second order: O.D.=0,9869(c.d.)2+2,4393(c.d.)+0,2666 (R2=0,9737) at 570 nm for Phormidium.