Pre-treatment of Ulva rigida improves its nutritional value for European seabass (Dicentrarchus labrax) juveniles

Macroalgae are promising ingredients for aquafeeds, but their recalcitrant polysaccharide structure limits their wide use. To disrupt this structure, different physical (ultra-sounds, autoclave, microwaves), chemical (acid, alkaline), and biotechnological (solid-state fermentation, SSF; SSF followed by sequential hydrolysis, SSF-SH) treatments were carried out in Ulva rigida. The chemical composition, morphological microstructure, release of reducing sugars, soluble protein, and phenolic compounds were evaluated in the final products.