Dunaliella salina, a halophilic unicellular chlorophyte, produces bioactive compounds and biofuels applicable to various industries. Despite its industrial significance, comprehensive studies on the morphological, physiological, and biochemical characteristics of the genus Dunaliella remain challenging. In this study, we characterized an axenically isolated green alga from a salt pond in Taean, Republic of Korea, and assessed its industrially relevant traits. The morphological characteristics were typical of D. salina, and molecular phylogenetic analysis of the SSU, ITS1-5.8S-ITS, LSU regions of rDNA, and rbcL gene confirmed the isolate as D. salina strain DSTA20. The optimal temperature, salinity, and photon flux density required for its growth were determined to be 21 °C, 0.5 M NaCl, and 88 µmol m⁻² s⁻¹, respectively. Dried biomass analysis revealed 42.87% total lipids, with major fatty acids, including α-linolenic acid (31.55%) and palmitic acid (21.06%). The alga produced high-value carotenoids, including β-carotene (2.47 mg g⁻¹ dry weight (DW)) and lutein (1.39 mg g⁻¹ DW), with peak levels at 0.25 M salinity. Glucose (195.5 mg g⁻¹ DW) was the predominant monosaccharide. These findings highlight the potential of D. salina DSTA20 for biodiesel production and as a source of ω-3 fatty acids, carotenoids, and glucose. Morphological traits provide insights relevant to the industrial potential of the species.

Asterarcys quadricellularis strain AQYS21, a green microalga isolated from the brackish waters near Manseong-ri Black Sand Beach in Korea, shows considerable potential as a source of bioactive compounds and biofuels. Therefore, this study analyzed the morphological, molecular, and biochemical characteristics of this strain; optimized its cultivation conditions; and evaluated its suitability for biodiesel production. Morphological analysis revealed characteristics typical of the Asterarcys genus: spherical to ellipsoidal cells with pyrenoid starch plates and mucilage-embedded coenobia. Additionally, features not previously reported in other A. quadricellularis strains were observed. These included young cells with meridional ribs and an asymmetric spindle-shaped form with one or two pointed ends. Molecular analysis using small-subunit rDNA and tufA sequences confirmed the identification of the strain AQYS21. This strain showed robust growth across a wide temperature range, with optimal conditions at 24 °C and 88 µmol m⁻²s⁻¹ photon flux density. It was particularly rich in ω-3 α-linolenic acid and palmitic acid. Furthermore, its biodiesel properties indicated its suitability for biodiesel formulations. The biomass of this microalga may serve as a viable feedstock for biodiesel production and a valuable source of ω-3 fatty acids. These findings reveal new morphological characteristics of A. quadricellularis, enhancing our understanding of the species.

Mychonastes homosphaera MHSC24 is a green microalga newly isolated from a brackish coastal site in Korea. This study represents the first indigenous record of this species in the country. It provides a comprehensive characterization of its morphological, molecular, physiological, and biochemical characteristics. This microalga was identified through morphological observations and multilocus phylogenetic analyses. Strain MHSC24 exhibited robust growth under mesophilic temperatures (15–27 °C), moderate light intensities (88–300 μmol photons m⁻² s⁻¹), and low salinity levels (0–10 PSU). Optimal growth was observed at 27 °C, 193 μmol photons m⁻² s⁻¹, and 0 PSU. Under standard cultivation, the strain exhibited high protein levels (~54% of dry weight, DW) and accumulated substantial amounts of canthaxanthin (5.59 mg g⁻¹ DW), the predominant carotenoid in its pigment profile. Thus, MHSC24 is a promising candidate for sustainable protein- and carotenoid-based applications. Palmitic acid (11.95 mg g⁻¹ DW) and galactose (2.07 mg g⁻¹ DW) were the predominant fatty acid and monosaccharide, respectively. The physiological resilience, high protein yield, and substantial canthaxanthin accumulation of MHSC24 support its potential utilization in the functional food, feed, and nutraceutical sectors. Therefore, this study provides a basis for optimized cultivation strategies and industrial exploitation of indigenous Korean microalgae.

Graesiella emersonii is a green microalga, belonging to the phylum Chlorophyta, with ecological and industrial significance. However, its phylogenetic position and mitogenome structure remain largely unexplored. We analyzed the complete mitogenome of G. emersonii GEGS21. This genome was 35,893 bp in length and contained 43 genes that comprised 13 protein-coding, six ribosomal RNA, and 24 transfer RNA genes. Phylogenetic analysis based on six protein-coding genes placed G. emersonii GEGS21 in a strongly supported clade with Pectinodesmus pectinatus, confirming its affiliation within the order Sphaeropleales. This study will provide valuable insights into the mitogenome architecture of G. emersonii, thereby contributing to further elucidation of green algal phylogeny and organelle genomic evolution.