Two-stage cultivation of Chlorella vulgaris using light and salt stress conditions for simultaneous production of lipid, carotenoids, and antioxidants

The effects of light and salt stress (NaCl and MgCl2) on the two-stage cultivation of Chlorella vulgaris, with or without a medium replacement, for the simultaneous production of lipid, carotenoids, and antioxidant compounds were investigated. The highest lipid productivity (15.59 ± 0.10 mg L−1 day−1) was obtained at 5 g L−1 MgCl2 and 140 μmol photons m−2 s−1 light intensity. The saturated fatty acids (SFA) ranged from 52.35–81.64%, monounsaturated fatty acids (MUFA) from 7.38–34.26%, and polyunsaturated fatty acids (PUFA) from 7.25–25.10%, with palmitic (C16:0), stearic (C18:0), and oleic (C18:1) acids as predominant fatty acids. Under high light intensity and nitrogen limitation in the two-stage cultivation, supplementation of 10 g L−1 NaCl with a medium replacement caused a marked increase in the total carotenoids (4.37 ± 0.33 μg mL−1). Cultivation of C. vulgaris in a medium containing 5 g L−1 NaCl or Mg Cl2, with or without a medium replacement step and with exposure to 140 μmol photons m−2 s−1 light intensity, led to enhanced antioxidant activities (65–79%). The different levels of antioxidant activities of the C. vulgaris extracts suggested the variation in the phytochemical compounds, a result of the stressed conditions.