Quantification of the total lipids in three aquaculture microalgae using BODIPY™ 505/515 stain and flow cytometry

Abstract

Microalgae are essential food sources for fish and shellfish aquaculture and contain abundant lipids with diverse fatty acid profiles. Quantification of total lipids in microalgae could assist commercial microalgal culture operations, harvest, and management in hatchery farms. Currently, reported protocols for lipid quantification are mainly for biofuel microalgal species. This study aimed to develop effective methodologies for total lipid quantification in three aquaculture microalgae using lipid-specific probe BODIPY™ 505/515 and flow cytometry. The objectives were to determine the effects of (1) staining concentration and time; (2) microalgal concentration; and (3) microalgal age. For Tisochrysis lutea, Chaetoceros muelleri, and Tetraselmis suecica, the optimal staining concentrations and times were 2.0 μg/mL for 0.5–30 min, 2.5 μg/mL for 5–30 min, and 1.5 μg/mL for 5–30 min, and the suitable algal concentrations were 5 × 10^5–6, 5 × 10^4–6, and 1 × 10^4–6 cells/mL. The total lipid accumulation in all three microalgae was contrary to the cell growth— low at the exponential growth stage and high at the stationary stage (beyond day 9). Overall, the methodologies developed in this study could be used to quantify total lipids in microalgae rapidly and accurately and require a small sample biomass (about 1 mL directly from algal culture). To produce microalgae with high total lipid accumulation, the best time to harvest may be at the stationary stage but not at the exponential growth stage. This study provided a better understanding of the lipid accumulation dynamics in the three aquaculture microalgae.