Improved pre-treatment for lipid staining of microalgae with a rigid cell wall

The worldwide depletion of energy and feedstock resources is an important topic of the current decade. Microalgae are an interesting option, offering rapid biomass production in combination with CO₂-fixation. For ongoing research in microalgae applications, well-functioning laboratory methods are important. One major aspect in microalgae-related studies is the measurement of the biomass' lipid content. In order to avoid elaborate extraction protocols, lipid staining with fluorescent dyes such as Nile Red or BODIPY is currently preferred in small-scale screening trials. Although practical, staining was hindered for microalgae with a rigid cell wall. Additional pre-treatment using solvents has already been described, but this was not sufficient for all strains. Besides sonication, we show here that fluorescent staining can be successfully implemented following the disruption of microalgal cell walls by bead beating. The protocol functions with conventional laboratory equipment (ball mill, shaker and vortex mixer), all of them allowing for small-volume samples and processing of multiple samples in parallel. The bead beating method extends the fluorescence lipid staining approach to microalgae with an extremely rigid cell wall and can be applied for screening trials in biofuel or biomaterial related research.