Growth and fatty acid profile of the marine microalga Picochlorum Sp. grown under nutrient stress conditions

Growth, proteins, carbohydrates and chlorophyll a as well as fatty acid compositions of a native marine microalga Picochlorum Sp. were studied in batch culture at light intensity 100 μ mol photons m−2 s−1, temperature 25 ± 1 °C and 16:8 h light and dark diurnal cycles using Walen medium. Under nutrient stresses, the cell counts and biomass productivity of the tested alga decreased as compared by control culture after 12 days. Carbohydrate content increased by nearly 21%, and 44% in the cultures grown in media supplemented with (−50% & −100% NaNO3), respectively. The proteins showed a remarkable decrease by 54% and 69.7% under the same conditions, respectively. chl a contents of Pichochlorum Sp. culture grown under N-starvation (−100%) decreased and also, a yellowish colour was recorded in the culture. The lipids increased by about 0.55, 1.6 folds in the cultures growing on the medium containing (−50% & −100% NaNO3), respectively and a decrease by 0.6% in those growing on the media containing nitrogen (+100% NaNO3), respectively. Considering phosphorus stress, the carbohydrate content increased by nearly 30.27%, 62.38% for the culture growing on −50% and −100% NaH2PO4·2H2O with respect to the control culture. The proteins showed a remarkable decrease by 24.5%, 37.3% in the culture medium containing the same concentrations, respectively. On the other hand, phosphorus deficiency (−50%) caused an increase in the chl a level of the cultures. Similarly, the lipids increased by about 2.2% and 2.5 folds in the cultures growing on the phosphorus deficient media (−50% & −100%), respectively. Fatty Acid Methyl Ester (FAME) was also found to be improved in algal cultures grown under nitrogen & phosphorus stress (−50% & −100%) which are mainly saturated fatty acids. The unsaturation of the FAME profile is crucial for the overall performance of the final produced biofuel. With further augmentations of lipid & carbohydrate content and improved fatty acids, the native microalga strain could be a potent candidate for aqua-culture feeding and or biofuel production.