Seaweeds biorefinery into pigments and carrageenans: Testing a sequential extractions approach

This study aims to test a sequential extraction (SE) method for red seaweeds ( Chondrus crispus, Mastocarpus stellatus, Gigartina pistillata ). The tested SE is a preliminary screening step towards the extrusion-based biorefinery (E2B2) of carrageenophytes into various natural products, a concept that still needs to be established. Phycobiliproteins, chlorophyll-a, carotenoids, and hybrid-carrageenans (HK) were isolated with the following sequence: cold-water extraction (CWE), ethanolic extraction (EE), hot water extraction (HWE), and hot alkaline extraction (HAE). HK chemical structures and gelling properties were systematically compared with those of carrageenans isolated from direct extractions (controls). Such comparison, which is critically missing in earlier SE studies, allows to assess the impact of prior extraction sequences on such HK properties. SE effectively separated algal components, facilitating the recovery of HK, particularly with M. stellatus and G. pistillata , with superior gel elasticity and viscosity compared to the controls. HWE yielded less sulphated HK with higher molecular masses and enhanced gelling properties. HAE extracts exhibited lower molecular masses and reduced gelation potential due to the prior HWE sequence. Prolonged extraction generally improved molecular masses and gels elasticity, although a distinct trend was found with C. crispus . The results from this preliminary screening suggest that M. stellatus is not a good candidate for testing in E2B2. • Sequential extractions (SE) separate hybrid carrageenans and pigments from carrageenophytes. • SE produce carrageenans with doubled gel elasticity compared to batch extraction. • Extraction times in each SE step must be optimized for each seaweed. • SE opens the way to the extractive extrusion-based biorefinery (E2B2) of seaweeds.