Untargeted metabolomics profiling of tropical marine microalgae in batch culture system with different mobile phase using Liquid Chromatography-Orbitrap High-resolution Mass Spectrometry combined with chemometrics

Microalgae have recently been identified as a valuable source of natural bioactive compounds, with potential applications suggested in areas such as food, animal feed, energy production (biofuels), fine chemicals, and pharmaceuticals. However, their chemical diversity remains largely unexplored and it is necessary to determine their potency for further application. This study will explore the diversity of chemical compound from six tropical marine microalgae with untargeted comparative metabolomics approach using a Liquid Chromatography-Orbitrap High Resolution Mass Spectrometry with different mobile phases. Six microalgae species were isolated from Jakarta Bay, Indonesia. Species identification was carried out using morphological and molecular identification. The isolates Chlorella vulgaris InaCC M205 (C5), Chlorella sp. 12 (C12), Tetraselmis subcordiformis InaCC M206 (T2), Tetraselmis sp. 5 (T5), Nannochloropsis oceanica InaCC 207 (N4), and Porphyridium purpureum (P) were then cultivated using f/2 media in 1 L glass photobioreactors, irradiated with daylight lamps (4000 lux) under a 12 h/12 h photoperiod at 25 ⁰C for until cultures reached the stationary phase. Biomass harvesting and measurements were carried out at the end of the culture period. The freeze-dry biomass then was analyzed using liquid chromatography-high resolution mass spectrometry. The results showed that biomass production on day 12 was not significantly different. Biomass production ranged from 0.8 to 1 g/L, with the highest production obtained from the C5 strain and the lowest from the C12 strain. Chromatography analysis revealed that untargeted metabolomics profiling of microalgae, using water-acetonitrile as mobile phase, identified potential compound markers such as N-Methyl-2-pyrrolidone, l-(+)-Cysteine, TBHQ and L-Phenylalanine, which can differentiate between species. Compound such as Cyromazine, Arachidic acid and 13(S)-HOTrE were the potential compound markers when using Water-Methanol as mobile phase. Our research indicates that the metabolomic profile of microalgae can be used to differentiate species depending on the choice of mobile phase.