A study on comprehensive utilization technology of seawater <italic>Spirulina</italic> biomass

As an important economic microalga, the efficient extraction and comprehensive utilization of bioactive compounds from Spirulina are crucial for enhancing its value. This study investigated the effects of different extraction sequences on the extraction efficiency, characteristics and economic benefits of phycobiliproteins, lipids, and polysaccharides from Spirulina. Six sequential extraction protocols were designed by integrating low-temperature extraction (phycobiliprotein), 95% ethanol extraction (lipid) and hot water extraction (polysaccharide), including 1) phycobiliprotein-lipid-polysaccharide (PLS); 2) phycobiliprotein-polysaccharide-lipid (PSL); 3) polysaccharide-phycobiliprotein-lipid (SPL); 4) polysaccharide-lipid-phycobiliprotein (SLP); 5) lipid-phycobiliprotein-polysaccharide (LPS); and 6) lipid-polysaccharide-phycobiliprotein (LSP). The extraction efficiency and characteristics of bioactive compounds were evaluated using UV-Vis absorption spectra, three-dimensional fluorescence spectra, infrared spectra, fatty acid composition, and monosaccharide composition. The results showed that phycobiliproteins should be extracted preferentially (yield: 68.29% in PLS, 66.77% in PSL), while heating or ethanol pretreatment induced its denaturation (yield vs 66.76% in PSL), while the fatty acid composition remained stable. Polysaccharide extraction efficiency declined markedly after protein or lipid extraction (71.80% in SPL, 39.90% in LSP and 19.57% in PSL). Infrared spectroscopy showed that the polysaccharides in each group had stable structures and there was no significant difference in monosaccharide compositions. Residual biomass analysis revealed the highest protein content in LPS-treated microalgal residue (71.4% DW). Sequential extraction enabled the recovery of phycobiliproteins, lipids and polysaccharides, but the extraction order critically influenced both yields and quality. The PLS sequence achieved the maximum economic value (162 RMB·kg-1), tripling the value of raw Spirulina powder (40 RMB·kg-1). This study provides theoretical and technical foundations for the full-component valorization of Spirulina biomass.