Microalgae of the genus Scenedesmus as a feedstock for biodiesel: characterization of the fatty acid profiles of total lipid isolates and assessment of the physicochemical properties of their transesterification derivatives

The fatty acid (FA) composition of total lipid (TL) isolates obtained from two strains of microalgae ( Scenedesmus obliquus IPPAS S-321 and Scenedesmus rubescens IPPAS D-292) grown in media with different ratios of principal nutrients were studied in the context of high-quality biodiesel production. In these experiments, the FA profiles of the studied microalgae could be successfully modified by application of nutritional stress, i.e. by limitation in the amounts of key nutrients – nitrogen, carbon, sulphur and phosphorus, supplemented to the growth medium. Thereby, the FA profile of S. obliquus IPPAS S-321 strain was featured with approximately equal proportions of saturated (predominantly stearic and palmitic acids) and unsaturated (predominantly oleic and α-linolenic acids) FAs, that indicated potential applicability of these microorganisms for highly efficient biodiesel production. The FA profiles of the lipid isolates obtained from the biomass of the S. rubescens IPPAS D-292 strain strongly dominated with unsaturated fatty acids (80.68–82.51%) while the saturated ones were much less abundant (17.48–19.25%). Such high contents of unsaturated FAs might assume lower applicability of the IPPAS D-292 strain for biodiesel production. Analysis of the physicochemical properties of the mixtures of FA methyl esters prepared from the biomass of S. obliquus IPPAS S-321 strain showed that, according to most calculated parameters (iodine value, cetane number, oxidative stability, viscosity), the acquired here lipid isolates meet the requirements of international standards EN 14214:2003 and ASTM D6751 − 2020. On the other hand, due to high contents of unsaturated FAs, the S. rubescens IPPAS D-292 strain was found to be non-compliant with these standards in a number of indicators. Thus, our results provide the basis for sustainable production of biodiesel from the Scenedesmus microalgae.