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

Abstract

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.

Microalgal biomass quantification from the non-invasive technique of image processing through red–green–blue (RGB) analysis

“…Moreover, these changes in microalgae culture, unlike in conventional agriculture which have a time window of days, must be taken in a few hours if a total loss of the crop is to be avoided (Gitelson et al, 2000). For this reason, an ideal biomass concentration measurement device would be based on a non-invasive methodology, in real time, with stable and low-cost sensors; it would also be fast, accurate and easy to apply (Lazcano-Hernández et al, 2019).…”

“…At present, the conventional methods most commonly used to estimate biomass concentration are varied, with advantages and disadvantages depending on the technique. Based on a classification of offline and online measurements, offline measurements are slow and invasive of the culture medium, having to extract a sample and analyze it in the laboratory, which complicates monitoring and delays measurement frequencies (Lazcano-Hernández et al, 2019). Among the best known offline methods is dry weight determination, which is problematic for small volume systems containing few cells (Chioccioli et al, 2014), and microscopic cell counting, which is time consuming and depends on the operator performing the count (Uyar, 2013).…”