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.

Keywords

• euglenophyte
• eutreptiella
• morphology
• molecular
• phylogeny
• fatty acid