Comprehensive amino acids profiling of microalgae by gas chromatography-mass spectrometry analysis after pre-column derivatization

Microalgae represent a sustainable protein supply compared to plant and animal sources. However, there is the need to characterize the full microalgae amino acids content, distinguishing among different species. In this work, a new efficient, fast, sensitive, reproducible and convenient gas chromatography-mass spectrometry (GC-MS) method, characterized by protein hydrolysis and derivatization performed in one-single-step, was validated for the determination of all amino acids in microalgal samples, including tryptophan. The overall optimized protein hydrolysis (improved in alkaline conditions due to tryptophan instability at acidic pH), the derivatization step (at neutral pH by using N-(tert-Butyldimethylsilyl)-N-methyltrifluoroacetamide) and the GC-MS method were validated. This methodology resulted selective, accurate (99.201 ± 7.61E-01 %), sensitive, reproducible and with a good recovery (96.20 ± 1.62E+00 %). Four commercial samples of Spirulina and three samples of Chlorella were analyzed. The resulting data were compared with the daily amino acid requirements identified by World Health Organization. The microalgae were found rich in the essential amino acids, including tryptophan, with a specific pattern associated to the species. Finally, by applying the principal component analysis, the intra/inter species differences of the amino acid profile of microalgae samples address them to specific uses, such as food in substitution of animal proteins or as food supplement.