From pineapple crown to multi-targeting bioactive compounds by solid-state fermentation using Aspergillus tubingensis

Due to its lignocellulosic structure, with phenolic compounds bound to it, pineapple crown (PC) has significant bioactive and technological potential. Solid-state fermentation (SSF) might be applied to promote the liberation of phenolic compound, increasing antioxidant capacity. This study aimed to valorize PC waste by fermenting PC (SSF) using Aspergillus tubingensis and further preparing an infusion from it, which could have improved antioxidant, antimicrobial and prebiotic properties. The ground PC was fermented for 7, 12 and 15 days (F7, F12, F15) at 25 °C. The free phenolic compounds were extracted with ethanol (80 %) and the bound phenolics were hydrolyzed. The infusion was prepared by steeping fermented samples in hot water (10 min). Antioxidant capacity (AC), phenolic profile (HPLC-DAD) and volatile compounds (SPME-GC-MS), physicochemical properties, sugars, xylooligosaccharides (HPAEC-PAD) and antimicrobial activity were evaluated. Fermentation affected the profile of volatiles, with F12 having the highest terpene content. Free and bound phenol content increased with fermentation, with F7 exhibiting higher antioxidant activity. HPLC-DAD analyses identified hydroxybenzoic acid, chlorogenic acid, p-coumaric acid, ferulic acid and vanillin. The infusion prepared with F12 showed better antioxidant results (5.31-21.23 mg TE. 100 mL^-1), while xylose and xylotriose detected in the infusions made with F7 and F12 suggest a prebiotic potential. The extracts and infusions of F0 and F7 showed antibacterial activity against all bacteria analyzed. Overall, SSF with A. tubingensis has significantly improved the bioactive properties of pineapple crowns and offers a sustainable strategy for the utilization of agro-industrial waste and the development of new value-added bioactive drinks.