Production of carbohydrates, lipids and polyunsaturated fatty acids (PUFA) by the polar marine microalga Chlamydomonas malina RCC2488

Polar microalgae that are highly productive in cold climates can produce large amounts of biomass and polyunsaturated fatty acids (PUFA). The polar Chlamydomonas malina RCC2488, grows at low temperatures and produces high amounts of lipids, which are mainly composed of PUFA. However, not much is known about its phylogenetic relationship with other strains within the order Chlamydomonadales and the optimum growth conditions for maximum biomass productivity have not yet been identified. In this study, a phylogenetic analysis was performed to determine the closest relatives of C. malina within the Chlamydomonadales order. To select the best growth conditions for maximum biomass productivities in cultivations performed at 8 °C, different salinities (0–80) and light intensities (70–500 μmol photons m⁻² s⁻¹) were tested, using bubble column and flat-panel photobioreactors. The effect of nitrogen limitation was tested to determine if C. malina can accumulate energy reserve metabolites (carbohydrates and lipids). Phylogenetic analysis confirmed that C. malina, which belongs to the Chlamydomonales order, is closely related to the psychrophilics Chlamydomonas sp. UWO 241 and Chlamydomonas sp. SAG 75.94, as well as to the mesophilic C. parkeae MBIC 10599. The highest biomass (527 mg L⁻¹ day⁻¹), lipid (161.3 mg L⁻¹ day⁻¹) and polyunsaturated fatty acids (PUFA; 85.4 mg L⁻¹ day⁻¹) productivities were obtained at a salinity of 17.5, light intensity of 250 μmol photons m⁻² s⁻¹ and nitrogen replete conditions. Strikingly, the marine C. malina can grow even in fresh water, but the biomass productivity was reduced. While the intracellular lipid content remained unchanged under nitrogen deprivation, the carbohydrate content increased (up to 49.5% w/w), and the protein content decreased. The algal lipids were mainly comprised of neutral lipids, which were primarily composed of PUFA. Chlamydomonas malina RCC2488 is a polar marine microalga suitable for high biomass, carbohydrate, lipid and PUFA productivities at low temperatures.