Integrated artichoke by-product biorefinery: Astaxanthin production from Phaffia rhodozyma and biocomposite development

Astaxanthin is a high-value xanthophyll carotenoid with strong antioxidant activity and wide applications in nutraceuticals, cosmetics, and aquaculture. Microbial production using the red yeast Phaffia rhodozyma (syn. Xanthophyllomyces dendrorhous) represents a sustainable alternative to chemical synthesis, but production costs are a key obstacle to its large-scale deployment. In this study, an integrated biorefinery strategy is proposed to valorise artichoke (Cynara scolymus L.) by-products as a low-cost substrate for P. rhodozyma fermentation. These by-products, rich in lignocellulosic polysaccharides and inulin, were subjected to a combined ultrasound and enzymatic pre-treatment under mild conditions, increasing the sugar release by 146% compared to the untreated control. The resulting hydrolysate supported yeast growth and astaxanthin production in a 5 L bioreactor, reaching 310.3 mg L 1 , with a final biomass of 15.8 g L 1 and almost complete depletion of sugars after 168 h. In a second valorisation step, the recovered fibrous fraction was used to prepare citric acid-crosslinked chitosan biocomposites with potential application as biodegradable food contact materials, which showed good thermal stability (T5% 170.87 ◦ C; Tmax 257.47 ◦ C) and a more ductile mechanical response (Young's modulus 189.33 MPa; elongation at break 17.83%) compared to the control consisting of chitosan, citric acid, and glycerol. Overall, this single-feedstock platform co-produces a high-value carotenoid and biodegradable composites, supporting circular bioeconomy options for artichoke supply chains.