Enhancement of BODIPY ^505/515 lipid fluorescence method for applications in biofuel-directed microalgae production

This paper describes a microalgal cell lipid fluorescence enhancement method using BODIPY ^505/515, which can be used to screen for lipids in wild-type microalgae and to monitor lipid content within microalgae production processes to determine optimal harvesting time. The study was based on four microalgae species (Dunaliella teteriolecta, Tetraselmis suecica, Nannochloropsis oculata, and Nannochloris atomus) selected because of their inherent high lipid content. An extended analysis was carried out with N. oculata due to the depressed fluorescence observed when compared with the other experimental strains. BODIPY ^505/515 lipid fluorescence was determined for two solvent pre-treatment methods (DMSO and glycerol) and four staining condition parameters (analysis time, staining temperature, dye concentration, and algal cell concentration). It was found that lipid fluorescence of thick cell-walled microalgae, such as N. oculata, is significantly enhanced by both the pre-treatment methods and staining condition parameters, thereby significantly enhancing lipid fluorescence by ca. 800 times the base autofluorescence. The lipid fluorescence enhancement method provides a quick and simple index for in vivo Flow Cytometry quantification of total lipid contents for purposes of species screening or whole culture monitoring in biofuel-directed microalgae production.