Evaluation of antioxidant, antimicrobial and prebiotic activities of a xylooligosaccharide-rich grape pomace extract

Background: Grapes are one of the most cultivated fruit crops worldwide, from which more than 70% is intended to wine industry that generates up to 20% of wasted biomass in the form of grape skin, seeds, stems and residual pulp, known as grape pomace (Spanghero et al., 2009; Corbin et al., 2015). Recently, extraction of xylooligosaccharides from lignocellulosic feedstocks has become very common, as these molecules have a potential impact on gastrointestinal health, mainly due to their selectively stimulation of gut microbiota – mainly via prebiotic and antimicrobial activities - but also for their antioxidant activity. The objective of this work was to evaluate the biological properties of a xylooligosaccharide-rich grape pomace extract. Method: Grape pomace extract was obtained through enzymatic extraction using 100 IU/g of an enzymatic cocktail produced by Aspergillus niger 3T5B8, containing xylanase activity. Extraction was performed using citrate buffer with pH 5 as solvent, and extraction was performed at 40 °C for 4 hours, under agitation. The extract was filtered under vacuum and lyophilized after adding 2% (w/w) of maltodextrin. Antioxidant, antimicrobial and prebiotic activities were evaluated. Results & Conclusions: The xylooligosaccharides-rich grape pomace extract presented low concentration of total phenolic compounds but high antioxidant activity (ABTS and DPPH methods). The extract presented antimicrobial activity against methicillin-resistant Staphylococcus aureus at concentration of 3% (w/w), and bacteriostatic activity against Escherichia coli and Salmonella enteritidis at concentration of 2% (w/w). Prebiotic activity was also evaluated using Lactobacillus and Bifidobacterium spp and results showed a relevant activity mainly upon Bifidobacterium spp. In conclusion, xylooligosaccharide-rich grape pomace extract presented relevant antioxidant, antimicrobial and prebiotic activities.