The non-consumable parts of plants such as peels, skins, husks, pods, fruit stones, stems, leaves, and pomace represent readily available secondary raw materials that can be used to produce energy, materials and chemicals, or as new and unconventional sources of functional ingredients.

The objective of this work was to evaluate walnut shells and pea pods as sources for the production of xylooligosaccharides (XOS). XOS are known to have a prebiotic activity. They are non-digestible oligosaccharides that are selectively metabolized by part of the human microbiota, with health benefits arising from the production of short-chain fatty acids and the stimulation of probiotic strains, such as bifidobacteria.

Hemicellulose from walnut shells and pea pods was obtained by combining different delignification and alkaline extraction parameters. Xylose was the predominant monomer in the fractions obtained, leading to a glucuronoxylan bearing some arabinose branches. Extracts obtained under optimal conditions were hydrolyzed to xylooligosaccharides using an endoxylanase. Maximum xylan conversion rates of 70% on walnut shells and 90% on pea pods were achieved, showing the interest of these two biomasses as sources of oligosaccharides with prebiotic activity.