Assessment of the Biodiesel Production Potential of the Amazonian Microalga Stigeoclonium sp. B23 under Different Nutritional Conditions

ABSTRACT Despite growing interest in microalgae for biodiesel, the quality parameters of biodiesel from Amazonian species remain largely unexplored. The rich biodiversity of the Amazon and the limited studies of its native microalgae make species such as Stigeoclonium sp. B23 promising candidates for sustainable and high-quality biodiesel. This study evaluated the effects of different nutritional conditions on fatty acid production and biodiesel quality in the Amazonian microalga Stigeoclonium sp. B23. Eight experimental conditions were established using modified BG-11 medium, combining the presence or absence of sodium nitrate with supplementation of sodium acetate (0.82 g L⁻¹) and/or sodium bicarbonate (0.42 g L⁻¹), to assess the impact of nitrogen limitation and alternative carbon sources. Among the tested experiments, the sodium nitrate depletion combined with supplementation of sodium acetate and sodium bicarbonate (Experiment 8) produced the most favorable fatty acid profile for biodiesel synthesis, with a cetane number of 77.1, oxidative stability of 7.07 h, and a saponification value of 127.3 mg g-1. Experiment 8 also showed a balanced composition of saturated (28.6%) and monounsaturated (6.4%) fatty acids. The biodiesel produced met all evaluated quality standards, including cetane number, iodine value, cold filter plugging point, and oxidative stability. These findings demonstrate the strong biotechnological potential of Stigeoclonium sp. B23 as a sustainable source of high-quality biodiesel.