Towards Microalgal Biorefinery: Multiproduct Fractionation of Phaeodactylum tricornutum by Liquid-Liquid Techniques

Phaeodactylum tricornutum is a promising biorefinery feedstock because it contains high-value compounds such as fucoxanthin and eicosapentaenoic acid (EPA), alongside other pigments, proteins, carbohydrates, and polyphenolics. However, downstream processing often targets single compounds, leaving possible co-products underutilised, thus limiting biomass valorisation. This study developed a multiproduct workflow for wet, disrupted P. tricornutum biomass by coupling solid-liquid-liquid extraction (SLLE) with centrifugal partition chromatography (CPC). The SLLE step used an ethyl acetate/n-butanol/water solvent system (3:2:5, v/v/v) and was optimised with respect to biomass loading and extraction time, yielding lipophilic, aqueous, interfacial, and insoluble primary fractions. Biomass content was the dominant factor governing partitioning into these fractions and target-compound recovery, whereas extraction time had a secondary influence. Under process-oriented optimised conditions of 1.3 h and 4.25% biomass content, fucoxanthin and EPA recoveries reached 91.3% and 70%, respectively. The lipophilic fraction was refined further by two-stage CPC, yielding high-purity fucoxanthin (99.4 ± 1.0%) and EPA-enriched glycerolipids (up to 99.9 ± 0.5%). Additionally, ten further fractions were obtained, including carotenoid-containing, chlorophyll, polyphenolic, protein-rich, and carbohydrate-rich fractions in the whole process. Overall, this twelve-fraction workflow supports the transition toward a scalable P. tricornutum biorefinery and provides a basis for assessing transferability to other microalgae.