Fucoxanthin and Polyunsaturated Fatty Acids Co-Extraction by a Green Process

Abstract

By their autotrophic nature and their molecular richness, microalgae are serious assets in the context of current environmental and societal challenges. Some species produce both omega-3 long chain polyunsaturated fatty acids (PUFAs) and xanthophylls, two molecular families widely studied for their bioactivities in the fields of nutrition and cosmetics. Whereas most studies separately deal with the two families, synergies could be exploited with extracts containing both PUFAs and xanthophylls. The purpose of our work was to determine cost effective and eco-friendly parameters for their co-extraction. The effect of several parameters (solvent, solvent/biomass ratio, temperature, duration) were studied, using two microalgal species, the non-calcifying Haptophyta Tisochrysis lutea, and the diatom Phaeodactylum tricornutum, that presents a silicified frustule. Analyses of PUFAs and fucoxanthin (Fx), the main xanthophyll, allowed to compare kinetics and extraction yields between experimental protocols. Co-extraction yields achieved using 96% ethanol as solvent were 100% for Fx and docosahexaenoic acid (DHA) in one hour from T. lutea biomass, and respectively 95% and 89% for Fx and eicosapentaenoic acid (EPA) in eight hours from P. tricornutum. These conditions are compatible with industrial applications.

Keywords: Phaeodactylum tricornutum; Tisochrysis lutea; cosmetics; food; fucoxanthin; green solvents; microalgae; polyunsaturated fatty acids.

Figure 1

Kinetics of fucoxanthin extraction from freeze-dried Tisochrysis lutea and Phaeodactylum tricornutum with ethanol (80 or 96%), methanol (100%) and ethyl acetate (100%). Extractions were carried out for 90 min at 30 °C (A,B) and for 24 h at 40 °C (C) with a 20:1 solvent/biomass ratio (v/w) in a closed system with magnetic stirring (n = 3 replicates).

Figure 2

Determination of particle size distribution (graphs) and scanning electron microscope observations at 30 µm scale of freeze-dried biomasses of Tisochrysis lutea (A,C) and Phaeodactylum tricornutum (B,D) crushed with mortar and pestle.

Figure 3

Kinetics of extraction of docosahexaenoic acid (DHA) from T. lutea (A) and eicosapentaenoic acid (EPA) from P. tricornutum (B) with ethanol (80 or 96%), methanol (100%) and ethyl acetate (100%). Extractions were carried out from freeze dried biomass for 90 min at 30 °C (A,B) and for 24 h at 40 °C (C) with a 20:1 (v/w) solvent/biomass ratio in a closed system with magnetic stirring (n = 3 replicates).

Figure 4

Comparison of the extraction yields of fucoxanthin (Fx) and total long chain polyunsaturated fatty acids (PUFAs) obtained with different ethanol/biomass ratios for 90 min at 30 °C (T. lutea) or for 24 h at 40 °C (P. tricornutum) with 96% ethanol in closed system with magnetic stirring. 100% references were determined from extractions with 96% ethanol (T. lutea) or 100% methanol (P. tricornutum) for Fx, and from direct transesterification of lipids from dry biomass into fatty acids methyl esters for PUFAs. Significant differences between data are represented by different letters. The relative ratios were compared for a given molecular family and species. (p-value ≤ 0.05, n = 3 replicates).

Figure 5

Cumulative extraction yields of fucoxanthin (Fx) and docosahexaenoic acid (DHA) from freeze-dried Tisochrysis lutea biomass with four successive 1 h extractions on the same biomass with a 10:1 (v/w) ethanol/biomass ratio (n = 3 replicates).