Improved Staining of Microalgae with Fluorescent Dyes Nile Red and BODIPY for the Determination of Neutral Lipids

Microalgae of different taxonomic affiliation, differing in cell wall structure and cultivation conditions, were effectively stained with BODIPY (2 µL of BODIPY working solution per 3 mL of culture) at different growth stages, which made it possible to estimate their content of neutral triacylglycerol lipids (TAG) using flow cytometry and fluorescence microscopy. The optimum staining time was 10 min. The obtained result can be applied to search for new effective strains of lipid-producing microalgae for their further application in the processes of third-generation biofuel production. The use of Nile Red (NR) dye requires the development of an individual staining protocol for each algal species under study, taking into account its morphological features and cultivation conditions. Effective staining of neutral lipids in algae characterized by rigid cell walls was achieved only by adding NR at a concentration of 10 µL per 1 mL of culture. The optimal concentration of NR for species with a “delicate” cell wall or surrounded only by a cytoplasmic membrane was 1 µL per 1 mL.