<![CDATA[Optimizing environmental factors in microalgal cultivation is essential for improving biomass and lipid production for biofuel applications. This study examined the effects of light intensity under 15% CO2 supplementation on growth, biomass, lipid and paramylon productivity, pigment content, and fatty acid methyl ester (FAME) composition in a local acidophilic E. gracilis strain cultivated at 500, 2,100, 4,500, 6,000, and 8,500 lux. The highest proportions of saturated, monounsaturated, and polyunsaturated fatty acids were observed at 8,500 lux (42.35%), 500 lux (59.01%), and 4,500 lux (23.705%), respectively. Methyl palmitoleate (C16:1) showed its highest relative abundance at 500 lux (32.46%), whereas its relative abundance at 6,000 lux was 26.34%. Biomass and lipid productivities were highest at 6,000 lux (0.0874 ± 0.0035 and 0.0311 ± 0.0030 mg/mL/day, respectively), while paramylon productivity was highest at 8,500 lux (0.030 ± 0.0011 mg/mL/day). The logistic growth model gave the highest maximum specific growth rate at 8,500 lux (0.78 day⁻¹). Chlorophyll a, chlorophyll b, and carotenoid contents peaked at 6,000 lux. The predicted biodiesel properties at 6,000 lux were an iodine value of 89.67 g I₂/100 g, a saponification value of 190.99 mg KOH/g, and a cetane number of 49.16. Overall, 6,000 lux provided the best balance for biomass and lipid production, whereas 8,500 lux favored paramylon accumulation. The FAME profile, particularly the high relative abundance of C16:1, supports further evaluation of this strain as a biodiesel feedstock.]]>
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