Characterization of Protosiphon botryoides KNUA219 Isolated from Dokdo Island as a Potential Biofuel Resource

The increasing demand for sustainable and eco-friendly energy sources has intensified research into alternative biofuel feedstocks. Microalgae, recognized for their rapid growth and production of high-value products, have emerged as promising candidates for third-generation biofuels. This study evaluates the potential of Protosiphon botryoides KNUA219, a microalga isolated from Dokdo Island, South Korea, as a biodiesel feedstock. Molecular and morphological analyses confirmed its identity, while growth experiments demonstrated its species-specific physiological characteristics, including an optimal pH range of 5−7, limited salinity tolerance, and high biomass productivity. Biochemical analysis revealed significant levels of carbohydrates (30.42 ± 1.65%), proteins (26.18 ± 1.14%), and lipids (14.86 ± 0.33%) in P. botryoides KNUA219, with glucose and galactose as the dominant monosaccharides. Fatty acid methyl ester profiling identified a lipid composition consisting of saturated (20.54%), monounsaturated (19.03%), and polyunsaturated fatty acids (42.65%), with palmitic, oleic, and linolenic acids as key components. Biodiesel quality assessments indicated compliance with critical standards for cetane number and cold filter plugging point, although optimization was required for iodine value and density. Proximate and ultimate analyses revealed favorable energy properties, including a high volatile matter content (88.94 ± 0.33%) and a calorific value of 23.11 ± 0.11 MJ/kg. These findings establish P. botryoides KNUA219 as a promising and sustainable resource for biodiesel production, while highlighting its potential for broader industrial applicability.