Single-stage fractionation of vine shoots using microwave heating

Abstract

Vine shoots are agricultural residues that can be used as a raw material in agro-biorefineries, in which their main constituents can be individually converted into valuable bioproducts. The treatment of vine shoots in uncatalyzed media containing water and 1-butanol enabled the single-stage separation of the major vine shoots constituents in different phases: the aqueous phase from treatments contained hemicellulose-derived products (mainly in the form of oligosaccharides), the organic phase accumulated the dissolved lignin, and the cellulosic fraction was recovered in solid phase. The aqueous phase from treatments was refined using membranes and processed with enzymes to obtain a refined product (RP) containing 92.2 g of oligosaccharides/100 g of non-volatile compounds. The oligosaccharides were mainly composed of anhydroxylose units substituted by acetyl and uronic groups. Enzymatic hydrolysis of RP with endo-xylanases reduced the average degree of polymerization to 2–3, which are preferred for application as healthy food ingredients. The solid phase from treatments was used as a substrate for enzymatic hydrolysis, enabling the production of solutions containing 34.9 g glucose /L and 4.2 g xylose /L.