SOLID-STATE FERMENTATION OF PINEAPPLE CROWN BY Aspergillus tubingensis: A STRATEGY FOR ENHANCED PHENOLIC COMPOUNDS AND ANTIOXIDANT CAPACITY

Due to its lignocellulosic structure containing bound phenolic compounds, pineapple crown (PC) has significant bioactive and technological potential. An alternative method for its extraction is solid-phase fermentation (SST), in which lignocellulolytic enzymes from filamentous fungi are used to promote its release. Therefore, the aim of this study was to evaluate the antioxidant capacity (AC) of PC and the extraction of phenolic compounds by SST with Aspergillus tubingensis. Except for the control (F0), 500 µl of saline solution (0.8%) containing the spores was pipetted into each Erlenmeyer flask. They were then fermented in BOD for seven (F7), twelve (F12) and fifteen (F15) days. Alkaline and acid hydrolysis of the pellets from the first extraction was performed for the bound compounds, while the free phenolic compounds were extracted with an 80% ethanol solution. The extracts were analyzed by HPLC-DAD. Total reducing compound content (TRC), total flavonoid content (TF) and AC values (DPPH, FRAP, ABTS and ORAC) were measured using a microplate reader. A total of 5 phenolic compounds were identified (4-hydroxybenzoic acid, ferulic acid, p-coumaric acid, chlorogenic acid and vanillin). p-Coumaric acid was the most important compound, followed by trans-ferulic acid. Vanillin was only present in PC and F0. In all samples, the bound extracts had higher TRC and TF. SST caused an increase in TRC and a decrease in TF compared to the controls. The TRC of the fermented samples ranged from 220.02 ± 24.04 to 639.63 ± 32.48 mg GAE/100 g and the TF showed values between 79.94 ± 15.92 and 142.75 ± 16.21 mg CE/100 g. The fermented samples showed an increase in AC, but the values varied according to time, type of extract and method (DPPH: 2268.99 ± 128.96; FRAP: 16686.15 ± 5254.2 mg TE/100 g). SSF of pineapple crown was effective to enhance phenolic compounds and AC.