Bioprospecting Ulleungdo‐isolated microalgae for carbon valorization and utilization

Abstract The growing demand for renewable energy alternatives has intensified global interest in microalgae as versatile bioresources for carbon valorization and bioenergy production. Owing to their rapid growth and biochemical versatility, microalgae provide a sustainable route for converting captured carbon into bioenergy and high‐value products. This study aimed to isolate and characterize three indigenous freshwater green microalgal strains – Chlorella sp. KNUA211, Desmodesmus sp. KNUA215, and Graesiella sp. KNUA220 – from the pristine habitats of Ulleungdo, Republic of Korea, and to evaluate their physiological and biochemical traits for bioenergy and bioproduct development. The strains were identified through morphological and molecular analyses using ITS, 18S rRNA, and tuf A markers, and comprehensively assessed for growth, pigment accumulation, biochemical composition, biodiesel quality, and carbon dioxide (CO 2 ) fixation. Chlorella sp. KNUA211 exhibited high protein content (37.06%) and superior biodiesel properties including cetane number 49.28 and oxidative stability 4.68 h, meeting ASTM D6751 and EN 14214 standards. Desmodesmus sp. KNUA215 showed the highest biomass productivity (2.02 g L −1 ), CO 2 fixation rate (0.56 g CO 2 L −1 day −1 ), and calorific value (24.77 MJ kg −1 ), indicating potential for carbon utilization and energy recovery. Graesiella sp. KNUA220 accumulated abundant pigments and polyunsaturated fatty acids, accounting for 58.47% of fatty acid methyl esters, supporting its application in nutraceutical and biochemical industries. All three Ulleungdo strains exhibited volatile matter contents exceeding 90%, suggesting enhanced combustibility and suitability for bioenergy applications. Collectively, these findings highlight Ulleungdo microalgae as promising native bioresources for integrated carbon utilization and renewable energy production.