Development of new green processes for the recovery of bioactives from Phaeodactylum tricornutum.

Two novel extraction techniques, pressurized liquid extraction (PLE) and microwave-assisted solvent extraction (MAE) have been evaluated for the recovery of bioactive compounds from Phaeodactylum tricornutum. Microalga P. tricornutum is rich in polyunsaturated fatty acids (PUFAs), such as EPA, and has a high content of the carotenoid fucoxanthin, which is a valuable pigment with several biological activities. Cells were disrupted at high pressure and then freeze-dried as a previous step to extraction. Additionally, only green solvents as water and ethanol (EtOH) - and mixtures of them - were used. For comparison purposes, the same response variables were considered in both processes: extraction yield (% w/w), total phenolic content (Folin-Ciocalteu assay), total carotenoids and chlorophylls, and antioxidant activity (ABTS assay, expressed as TEAC value). Factorial experimental designs were employed for both PLE and MAE optimization, being %EtOH in water and temperature the common experimental factors. Extraction time was also a factor considered for optimization in MAE. A detailed chemical characterization of pigments was performed by HPLC-DAD-MS/MS (high performance liquid chromatography-diode array detector-mass spectrometry), being fucoxanthin the main compound extracted. Optimum extraction conditions were 50°C, 100% EtOH, 20min for PLE, while optimum conditions for MAE were 30°C, 100% EtOH and 2min. Both technologies extract fucoxanthin as a main compound but higher recoveries were achieved using PLE due to a higher extraction yield. In addition, both MAE and PLE extracts contained different lipid classes potentially enriched in EPA, given an added-value to the extracts.