Enzymatic production of cello-oligosaccharides with potential human prebiotic activity and release of polyphenols from grape marc.

Grape marc, the main winemaking byproduct, is an excellent source of bioactive polyphenols, such as anthocyanins, resveratrol and quercetin. An enzyme-catalysed treatment of marc was developed using endo-1,4-β-d-glucanase to release polyphenol O-glucosides and simultaneously generate the optimal concentration of water-soluble cello-oligosaccharides (COS), including cellopentaose, cellotriose, and cellobiose from the marc matrix. The prebiotic properties of marc hydrolysate rich in COS was assessed using human probiotic monocultures of Lactobacillus spp. and Bifidobacterium spp. strains, and invitro human faecal fermentation. The COS-rich hydrolysate showed excellent prebiotic effect in both studies, successfully supporting the growth of beneficial probiotic strains, and was highly fermentable by faecal microbiota producing gas and short chain fatty acids. Acetate and propionate production were the highest when faecal bacteria fermented COS-rich solution compared with standard substrates. For the first time, COS was shown to be fermented by faecal microbiota, demonstrating the potential benefits of valorised grape marc.