Microalgae as a sustainable alternative to palm oil: fatty acid profiles under photoautotrophic and heterotrophic growth

Palm oil is the world's most widely used vegetable oil, with a sizeable impact on the environment. As an alternative, microalgae are considered oil producers since they produce a variety of fatty acids (FA) depending on growth conditions. A collection of ten microalgae strains naturally producing oils similar in composition to palm oil was selected, and the effects of cultivation regime and varying light intensity on their growth and FA production and composition were analysed. To achieve high biomass density as well as total fatty acid (TFA) content, the optimum irradiance of 400 µmol photons m^-2 s^-1 in a photoautotrophic regime was determined for most of the strains. The growth rates of Scenedesmus and Desmodesmus strains in general were approximately twice as high as Chlamydomonas. The highest TFA content was found in S. obliquus CCALA 455 and D. subspicatus CCALA 467, grown photoautotrophically, reaching the values of about 66% and 58% of their dry weight, respectively. Moreover, the content of palmitic (PA), oleic (OA) and linoleic acid (LA) of about 39%, 30% and 14% of TFA, respectively, determined in D. subspicatus CCALA 467 was closest to that in palm oil (44% of PA, 39% of OA and 10% of LA). Eight of the ten microalgae strains were capable of heterotrophic growth, although their production under this regime has not been considered suitable in terms of TFA and individual FA content. KEY POINTS: • The optimum irradiance of 400 µmol photons m^-2 s^-1was determined • CCALA 467 produces selected FAs in amounts close to those in palm oil • TFA content (% of dry weight) in CCALA 467 is 1.6-fold higher than in the palm.