Rapid triacylglyceride detection and quantification in live micro-algal cultures via liquid state 1H NMR

Non-invasive methods for measuring lipid content in live microalgal cultures are critically needed for algal biofuel research and development. A non-destructive method requiring minimal sample preparation was developed utilizing liquid state ¹H NMR for quantifying triacylglycerides (TAGs) in live algae cultures. ¹H NMR and ¹H HR-MAS spectra of live algae cells show outstanding correlation with published chemical shifts for TAGs. ¹H NMR spectra of Chlamydomonas reinhardtii whole cells and isolated lipid bodies were compared with a standard oleic TAG ¹H spectrum, demonstrating that only lipid body TAGs were observed. A “model” TAG was derived, providing a proton count and molecular weight for conversion of TAG ¹H NMR integrals to volumetric TAG or fatty acid methyl ester (FAME) equivalent concentrations, which were correlated to FAME concentrations by gas chromatography (FAME-GC) at several time points. A customized NMR flow cell was subsequently constructed, allowing real-time, continuous measurements of multiple cultures. ► ¹H NMR method for detection of triacylglycerides in live microalgal cultures. ► Quantitation model TAG includes weighted average MW and proton count. ► ¹H NMR and FAME-GC data correlated throughout a growth cycle. ► A flow NMR probe was constructed to provide real-time TAG measurements.