Two pronounced Chlorella strains for efficient biodiesel feedstock production

Abstract

In this study, two indigenous Chlorella strains were evaluated for triacylglycerol (TAG) production and related parametersduring 10 days of N-deprivation. The strains were identified based on morphological characteristics and genomic information, namedas Chlorella sp. IMU12 and Chlorella sp. IMU17. Time-dependent reduction of growth was accompanied by decreased chlorophyllcontent, reduced oxygen evolution ratio, and elevated carotenoid content of both strains cultivated in N-free Bold’s basal medium.Nitrogen deprivation induced total lipid and neutral lipid content in both strains, supported by FTIR measurement of TAGs. Chlorellasp. IMU17 showed higher production of TAGs as a response to N-deprivation. Strikingly, relative polysaccharide content showed arapid increase on the first days and a noticeable reduction was recorded especially after 5 days of N-deprivation while TAG productionshowed a gradual increase during the whole period of N-deprivation in both strains. Starch might be a predominant form of carbonstorage in the short term and the continuous increase of TAG production might be supported by degradation of starch in a longerperiod of N-deprivation. FAME analysis of lipids showed that the saturation level of the fatty acids of both strains meets the Europeanstandard EN 14214 requirements. Lastly, N-deprivation stimulated a significant reduction of PUFA production in Chlorella sp. IMU17.Thus, Chlorella sp. IMU17 might stand as a promising candidate for biodiesel feedstock production with its low PUFA content and aconcomitant induction of saturation of fatty acids as a clear response to N-deprivation.