Improving the reliability of fluorescence-based neutral lipid content measurements in microalgal cultures

► An optimized Nile-Red fluorometric method with reduced variability is proposed. ► The microplate-based technique allows fast and reliable neutral lipid quantitation. ► Confidence in the use of Nile Red as a quantitative staining agent is improved. ► Proposed method can be used for culture monitoring and process condition screening. ► BODIPY was unsuitable for quantifying oil content in the microplate-based technique.