A new omega-3 rich euglenoid Eutreptiella sp. from the Korean coastal waters

Euglenoids, the primary producers of fatty acids (FAs), are used in functional foods, feeds, and biofuels. Long-chain polyunsaturated FAs (LC-PUFAs) such as eicosapentaenoic acid and docosahexaenoic acid (DHA) are crucial for human health. The primary commercial source of LC-PUFA is fish; however, its heavy metal bioconcentration is concerning. Globally declining wild-harvested fish stocks is another recently recognized serious problem. Herein, the morphology, molecular phylogeny, matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectroscopy, and FA compositions of an unspecified euglenoid strain KCTC 19016P isolated from the Korean coastal waters were examined. The vegetative cells were longitudinally spindle-shaped with a truncated apex and a tail-like extension at the anterior and posterior ends, respectively and had two unequal flagella. They had distinct red eyespots, numerous chloroplasts, and paramylon granules. Pellicular cell striations were easily observed using a scanning electron microscope. Phylogenetic analyses based on nuclear and chloroplast small-subunit ribosomal RNA sequences revealed that Eutreptiella sp. KCTC 19016P was nested within the Eutreptiella clade and was closely related to Eutreptiella marina (AY703209). Using the MALDI-TOF spectrum analysis, we differentiated between Eutreptiella sp. KCTC 19016P and the related NIES strains, thereby confirming their taxonomic similarities. Eutreptiella sp. KCTC 19016P growth was observed for 30 days; the maximum growth rate and doubling time was 0.50 ± 0.05 day⁻¹ and 1.40 ± 0.15 day, respectively. Eutreptiella sp. KCTC 19016P had a relatively high monounsaturated FA percentage compared to the other species. The omega-3 FA content in Eutreptiella sp. KCTC 19016P was significantly higher than that of the other strains, as determined using ordinary one-way analysis of variance (P < 0.0001). Among the four euglenoids, Eutreptiella sp. KCTC 19016P had the highest α-linolenic acid and DHA contents. Thus, this new isolate could potentially be used in aquaculture and nutraceuticals without the risks associated with consuming fish.