High-resolution magic angle spinning 1H NMR analysis of whole cells of Thalassiosira pseudonana (Bacillariophyceae):: Broad range analysis of metabolic composition and nutritional value

Chemical composition of the microalga Thalassiosira pseudonana Hasle & Heimdal was studied with different proton nuclear magnetic resonance (H-1 NMR) techniques, and by comparing NMR spectra from extraction samples with a spectrum from a sample of whole cells we show that high-resolution magic angle spinning (HR MAS) H-1 NMR can be used for broad range analysis of metabolic composition in microalgal whole cells. Signals from important metabolites such as polyunsaturated fatty acids (PUFAs) eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids were seen in a H-1 NMR spectrum of lipophilic extract, and possibly also signals from the carotenoid fucoxanthin. In a spectrum of hydrophilic extract we assigned signals to amino acids such as glutamine (Gln) and glutamic acid (Glu), carbohydrate and ATP. These findings were compared to a spectrum of HR MAS H-1 NMR analysis of whole cells, where it was possible to find signals coincident with the different metabolites seen in spectra of the extraction samples. Since the position of resonance peaks in a NMR spectrum depends on the chemical surroundings of each atom at the time of analysis some peak shift differences between extract and whole cell sample spectra may occur, but signal shifts were not significantly different between the analyses here. In addition, application of HR MAS highly increased spectral resolution in the complex whole cell sample. We therefore suggest that HR MAS H-1 NMR analysis is a suitable analysis tool to study metabolic composition directly on whole cells of microalgae, making it possible to study a broad range of metabolites simultaneously without tedious extraction procedures.