Off-line and on-line optical monitoring of microalgal growth

The growth of Chlamydomonas reinhardtii microalgae cultures was successfully monitored, from classic off-line optical techniques (optical density and fluorescence) to on-line analysis of digital images. In this study, it is shown that the chlorophyll fluorescence ratio F685/F740 has a linear correlation with the logarithmic concentration of microalgae. Moreover, with digital images, the biomass concentration was correlated with: the luminosity of the images through an exponential equation, and the length of penetration of a superluminescent blue beam (λ=440 nm), through an inversely proportional function. Outcomes of this study are useful to monitor both research and industrial microalgae cultures.