Integrated Analytical Approach to Micro- and Macroalgae: Tailored Extraction Strategies for Sustainable Biorefineries

This study evaluates the solvent-dependent extraction of Arthrospira platensis and Ascophyllum nodosum to guide sustainable marine biorefinery design. SOXTHERM rapid extractions were performed with n-hexane, ethanol–water (1:1, v/v), and water under controlled severity (3 h, n = 2). Ethanol–water consistently delivered the highest yields for A. platensis (25% DW ± 2.2) and A. nodosum (26% DW ± 2.2), with differences confirmed by a permutation test (p < 0.05). Hexane selectively enriched lipophilic fractions, whereas water favored polar constituents. For A. platensis, ethanol–water exceeded hexane (Δ20.3% DW ± 2.5) and water (Δ15.0% DW ± 1.2). For A. nodosum, differences were smaller versus water (Δ3.5% DW ± 3.6) but pronounced versus hexane (Δ23.5% DW ± 1.5). A. platensis extracts were protein-rich and contained long-chain polyunsaturated fatty acids, while A. nodosum extracts exhibited a high mineral content and structural carbohydrates. Ultra-high-resolution FT-ICR-MS revealed thousands of molecular features, including putative lipid-like and nitrogenous species; all structural assignments remain putative without MS/MS confirmation. Notably, biopterin analogues were detected in A. platensis water extracts, and polyphenolic signatures dominated A. nodosum ethanol–water extracts. Operationally, ethanol–water is recommended for scouting wide compositional space, while processing micro- and macroalgae requires desalting and antifoam strategies to mitigate foaming during polar extractions.