Possibilities and limitations of non-destructive monitoring of the unicellular green microalgae (Chlorophyta) in the course of balanced growth

Abstract

Timely information about basic growth parameters, such as dry weight, cell number, and pigment (chlorophyll and carotenoid) content is of importance for the evaluation of physiological conditions and growth kinetics of microalgal suspension cultures. The possibility of non-destructive determination of these parameters using the optical density (total light attenuation due to light scattering and absorption by the microalgal cells and the pigments contained therein) spectra of the cell suspension was shown for unicellular green algae Ettlia carotinosa Komarek and Haematococcus pluvialis Flotow (Chlorophyceae). Estimation of the pigment content of morphologically heterogeneous cultures (such as H. pluvialis) with a reasonable accuracy required the light-scattering compensation of the measured extinction spectra. On the other hand, the scattering signal is useful for dry weight and cell density estimation (in the cultures with insignificant morphological heterogeneity). The spectral regions sensitive to the variation in the target culture parameters was found, and the spectral indices linearly correlated with the latter were constructed. The possibilities and limitations of the optical methods suitable for non-destructive monitoring of the microalgal cultures in the course of their balanced growth and the potential of the developed approach for microalga biotechnology are discussed.