Fungal biodegradation of ellagitannins extracted from rambutan peel

Abstract

The rambutan peel is a by-product with a high quantity of ellagitannins. When ellagitannins are biodegraded, they produce ellagic acid. This work aimed to extract ellagitannins from rambutan peel and make a solid-state fermentation (SSF) to identify which enzymes are involved in the biodegradation of ellagitannins. Extraction of rambutan ellagitannins (RE) was done by microwave/ultrasound technology, isolated by column chromatography with Amberlite XAD-16 resin, and characterized by HPLC-MS. The SSF was done using RE as substrate at three different concentrations (7.5, 15, and 22.5 g/L), Aspergillus niger GH1, polyurethane foam as support and Czapeck-dox medium in tray reactors. Enzymatic activities cellulase, xylanase, polyphenol oxidase, ellagitannase, tannase, β-glucosidase and α-L-arabinofuranosidase were tested, and ellagic acid was quantified. The microwave/ultrasound allowed the extraction of seven ellagitannins where the major compound was geraniin. SSF allows the biodegradation of geraniin into ellagic acid, and ellagitannase was the enzyme with the highest value (25.49 U/L) at the times of maximum accumulation of ellagic acid (6–12 h of fermentation), indicating that this enzyme is directly associated to the process of biodegradation. Finally, the maximum titles of this enzymatic activity (353.27 U/L) were found at fermentation time of 42 h and RE concentration of 22.5 g/L.