The freshwater alga Chlorella sorokiniana tolerates salt stress via modulating metabolites and minerals

Salinity stress is a laborious environmental stress for freshwater microalgae that can be overcame via modulating some physiological traits. This study assessed the impact of salt stress on growth and physiology of the freshwater alga Chlorella sorokiniana . The alga was exposed to salt concentrations of 0, 140, 270 and 340 mM NaCl in the BG11 basic growth medium with pH of 7.5 ± 0.20 for 43 d. Growth, in terms of the cell number, of Chlorella sorokiniana was progressively decreased with increasing salinity levels. Nevertheless, the salinity-induced reduction in the content of photosynthetic pigments (chlorophyll a, chlorophyll b and carotenoids) was most evident at 270 mM NaCl. Salinity led to progressive increase in the concentrations of protein, soluble sugars, starch and minerals (Na + and K + ) and lipids above the control. The present findings suggest that C. sorokiniana can withstand salinity stress up to 340 mM via enhancing production of lipids and compatible organic solutes such as proline with minor contribution of protein, soluble sugars and mineral ions (Na + and K + ) .