Characterization and Potential Utilizations of A Marine Euglenophyte from Okinawa, Japan

Abstract

mong many microalgae species, certain euglenophytes stand out as
excellent sources of valuable natural components with diverse
biotechnological applications. This study focused on investigating the identity
and potential utilizations of a green marine euglenophyte, namely EKoku01,
isolated from the brackish Kokuba River in Naha City, Okinawa, Japan.
Morphologically, cells of EKoku01 were 12-30m long and 8-10 m wide,
displaying dynamic changes during euglenoid motility with a distinctively
striated pellicular body. Notable features included two uneven flagella, an
eyespot, and multiple green discoid chloroplasts. The 18S rDNA molecular
phylogeny positioned Ekoku01 within Clade 1 of Eutreptiella, comprising
strain CCMP389, CCMP-1594, and LIS 2000, which was distantly related to
other known marine euglenophytes (i.e., the genus Eutreptia and Clade 2 of
Eutreptiella). Based on the morphology and molecular phylogeny, EKoku01
was identified as Eutreptiella sp., representing the first recorded species of
this genus in Okinawa, Japan. EKoku01 showed an optimum growth
performance at 20 oC (max. =0.17 ± 0.037 day-1) and exhibited an unusually
strong positive phototaxis response towards a light source. Its fatty acid (FAs)
profile comprised predominantly saturated FAs (69.8%), polyunsaturated FAs
(15.1%, with two omega-3 FAs), monounsaturated FAs (3.6%), and branched
FAs (4.4%), while ~7.1% remaining unidentified. Based on its growth
performance, FAs composition, and light sensitivity, we proposed several
potential utilizations of this strain (e.g., as a source for nutraceutical,
pharmaceutical, food, and aquaculture applications), including the use of
EKoku01 as a model organism for developing an innovative light-driven cell
concentration system based on phototaxis.