Salinity stress has been verified to be a successful approach to enhance lipid production in high-starch marine algae, and salinity-induced carbon flow switching has been proposed as an algal response specific to brackish water. With the aim of testing this assumption, Chlorella sorokiniana SDEC-18, a low-starch freshwater alga, was grown in BG11 medium with NaCl addition at various concentrations (0, 2, 5, 10, 20, and 30 g/L). The results showed that salinity stress promoted carbon redistribution and starch conversion to lipid. The most desirable lipid productivity of 19.66 mg/L·d occurred in the medium with 20 g/L NaCl, about 2.16 times as high as that in the BG11 medium control. Moreover, microalgae with salinity stress were able to produce biodiesel with a more suitable cloud point, due to a decrease in the saturated fatty acid content. This therefore confirms that low-starch freshwater microalgae can also carry out salinity-induced carbon flow switching.
Keywords: Carbon partitioning; Freshwater algae; Low-starch algae; Salinity stress; Starch-to-lipid shift.
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