Influence of macronutrient concentration on the growth, photosynthetic pigment content, and fatty acid composition of the microalga Scenedesmus rubescens

The rise in greenhouse gas emissions and the depletion of fossil fuel reserves threaten sustainable development and public health. In this context, microalgae are receiving increasing attention owing to their high productivity and broad biotechnological potential. Species of the genus Scenedesmus are considered promising raw materials for biodiesel production as well as for obtaining natural pigments with diverse biological activities. This study examines the effect of nutrient medium composition on the growth, pigment accumulation, and fatty acid profile of the microalga Scenedesmus rubescens D-292. The microalga has been cultivated in Gromov’s medium with varying concentrations of KNO₃ (0.1, 1.0, and 10 g L-1), K₂HPO₄×3H₂O (0 and 0.262 g L-1), MgSO₄×7H₂O и NaHCO₃ (0, 0.2, and 2.0 g L-1). The highest growth rate, pigment content (10 mg g-1 dry biomass) and proportion of polyunsaturated fatty acids (65% of total fatty acids) has been observed under sulfur-rich conditions (2.0 g L-1 MgSO₄×7H₂O) combined with nitrogen, phosphorus, and carbon limitation. The highest fatty acid yield (229.9 mg g-1 dry biomass) has been obtained under carbon-rich conditions (2.0 g L-1 NaHCO₃) with limited availability of other macronutrients. The lipid profile of the strain has been dominated by palmitic (14.4–17.5 %), oleic (13.8–29.1 %), linoleic (10.1–13.8 %), and α-linolenic (19.7–36.7 %) acids. Although the strain exhibits limited potential for biodiesel production, it demonstrates potential as a source of natural pigments and lipids rich in polyunsaturated fatty acids, particularly α-linolenic acid (up to 37% of total fatty acids).

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