Effect of nitrogen and carbon sources and salt stress on the bioactive components concentration in Scenedesmus obliquus

Abstract

In Scenedesmus obliquus culture, the effects of different nitrogen and carbon sources and saline stress on total carotenoids, total proteins and total phenols contents were investigated. Microalgae in Allen & Arnon culture medium were cultivated, until reaching the stationary phase. Then, sodium nitrate or urea as nitrogen source and sodium acetate or glucose as carbon source, were incorporated. Additionally, sodium chloride was added for cause saline stress. Fourteen treatments were carried out, during 40 days. Differences in bioactive components concentration were observed for the different nitrogen and carbon sources from day 26. When 0.24 g/L of urea were used, 3 times more of total carotenoids were obtained than when sodium nitrate was used; while, with 3.68 g/L of glucose, 1.5 times more of total carotenoids were reached than with sodium acetate was used. Total proteins concentration was 1.9 times higher when 0.24 g/L of urea and 5.02 g/L of sodium acetate were utilized as nitrogen and carbon sources, respectively. With 31.00 g/L of urea 4 times more of total phenols were obtained than with sodium nitrate; while, 12 times more of total phenols were achieved with 3.68 g/L of glucose than with sodium acetate. Saline stress caused a reduction in the bioactive components of interest. The highest concentrations obtained were: 513.20±13.21mg β-carotene/gdwc, 7.25±0.34 mg BSA/gdwc, and 16.78±0.54 mg GAE/gdwc. Therefore, this study confirmed that Scenedesmus obliquus microalgae developed strategies to adapt to the new conditions caused by the nitrogen and carbon sources incorporation, causing changes in the concentration of bioactive components.