Effect of culture temperature on fatty acid composition of diatom Cylindrotheca closterium

Abstract

Fish oil is widely used as a source of essential long chain poly-unsaturated omega-3 fatty acids, such eicosapentaenoic (EPA) and docosahexaenoic (DHA), for aquaculture. However, there is increasing interest in reducing the aquaculture industry?s dependence on this resource due to its unsustainability and variable cost and supply. Marine microalgae naturally produce EPA and DHA fatty acids and they content can be modified by manipulation of the growth conditions. The aim of this study was to assess the effect of temperature on fatty acid composition of the marine diatom Cylindrotheca closterium. To that end, C. closterium was grown in a photobioreactor: a) at 20 °C (control) and b) lowering the temperature from 20°C to 11°C in the stationary growth phase. Total lipid content and lipid fractions were determined spectrophotometrically and gravimetrically. Gas chromatography was performed to analyze fatty acid composition. C. closterium growth was not affected by temperature variation, as showed by cell density and dry weight determinations. When the temperature was lowered, triacylglyceride content significantly increased compared to the control condition. In addition, among omega-3 fatty acids, DHA and EPA showed a marked increase. Thus, these results evidence the potential of this strain as an alternative and sustainable source for aquaculture purposes.