Applicability of differential fluorescein diacetate and propidium iodide fluorescence staining for monitoring algal growth and viability

Microalgae can be cultivated for producing high-valued products through the production of enzymes to offset the cost of CO2 sequestration, providing financial incentives. The viability of algae in the photobioreactor needs to be monitored to ensure biologically active live cells. In this study, we explored a simple fluorometry method for differentiation of live and dead algal cells in photobioreactors by fluorescein diacetate (FDA) and propidium iodide (PI) fluorescence staining. FDA stains fluorescent green to the living cells while PI stains the dead cells, allowing the discrimination of live and dead cells. The method was evaluated using two green algae and two strains of cyanobacteria grown in shake flasks and a continuously stirred photobioreactor. The method was found applicable for Chlorella pyrenoidosa and Synechococcus 7002 but was not applicable for the cultures of Scenedesmus dimorphus and Synechococcus elongatus 7942. We conclude that FDA is a good stain for monitoring live algal cells in photobioreactors but its applicability to individual species of algae must be evaluated.