Green Protocols for the Isolation of Carbohydrates from Vineyard Vine-Shoot Waste

Abstract

Annually large amounts of vineyard waste are produced from vine pruning. Romania has a vineyard of 183,000 ha and produces 6.0 million hl of wine/annum, being ranked 10th in the world and 5th in Europe, after Spain, France, Italy, and Portugal. Currently, the waste is incorporated into the soil or burned in open field, leading to increased greenhouse gas emissions. The extraction of cellulose, hemicellulose, and lignin from vine-shoot waste is a primordial step for the integral valorization of these resources. The study aims to obtain carbohydrates from vine-shoot waste from Romanian grape varieties by using an innovative method for the transformation of vine-shoot waste into valuable compounds. Microwave pretreatments were performed using different operational conditions: temperature (150–180 °C) and residence time (10–30 min). The pretreated vine-shoot waste was delignified with sodium chlorite for lignin removal and then enzymatically hydrolyzed using new types of enzymes (cellulase from Trichoderma reesei and β-glucosidase). A maximum of 14 g glucose can be obtained from 100 g vine-shoot waste by microwave pretreatment (165 °C for 20 min), delignification, and enzymatic hydrolysis for 80 h. It can be concluded that the vine-shoot waste may be used as a raw material for bioethanol production by using a green technology in the context of circular economy objectives.