Accomplished High-Resolution Metabolomic and Molecular Studies Identify New Carotenoid Biosynthetic Reactions in Cyanobacteria.

Cyanobacteria and microalgae are characterized by a rich and varied profile of chlorophyll (8-20 mg/g) and carotenoid (>2.2 mg/g) pigments, being noteworthy material for natural pigment production in the food industry. We propose a systematic workflow that uses high-performance liquid chromatography (HPLC) coupled with high-resolution tandem mass spectrometry in a broadband collision-induced dissociation mode (bbCID) acquisition mode to simultaneously obtain MS and MSn spectra. Metabolomic studies showed for the first time the presence of carotenoids with 5,6-epoxy-groups (5,6-epoxy- and 5,8-furanoid β-cryptoxanthin), carotenoids from the α-branch (5,8-furanoid-2'-3'-didehydro α-cryptoxanthin), and 2'-dehydrodeoxomyxol in cyanobacteria. To support the new findings, an in silico search retrieved the putative sequences of carotenogenic enzymes involved in the corresponding biosynthetic pathways (ZEP, NSY, CrtL-b and CrtR) in the analyzed cyanobacteria species. Consequently, high-throughput metabolomics studies assisted by molecular analysis offer a powerful tool for providing insights into the characterization of bioactive compounds and their metabolism in cyanobacteria and microalgae.