Bioconversion of vine shoots into renewable products using ohmic heating extraction and autohydrolysis

Abstract

The valorization of vine shoots (VS), a lignocellulosic waste from the viticulture industry, was evaluated using different alternative and sustainable extraction processes. An innovative biorefinery approach, sequentially combining ohmic heating extraction (OHE) and autohydrolysis (AH), was selected for the extraction of nutraceutical compounds and bioethanol production. Overall, the use of both technologies improved the extraction yield of target compounds, modulated their profiles (due to the affinity of each solvent used), and improved the saccharification of the residual biomass when compared to non-sequential processing, reinforcing the advantages of the novel approach proposed. An optimal combination of OHE (80 °C for 60 min) followed by AH at 200 °C for 30 min showed the highest recovery of phenolic compounds (31.3 mg GAE/g VS) and antioxidant activity (48.5 mg TE/g VS with FRAP methodology). Simultaneously, the recovery of glucose in the solid fraction (96.3 %) was promoted, making it suitable for simultaneous saccharification and fermentation, with ethanol yields of up to 61.26 % (achieving 20.57 g/L after 72 h). The novel cascading valorization process applied in this work maximizes the extraction of value-added products and aligns with circular economy principles by promoting the efficient use of this agro-industrial waste, reinforcing the importance of environmentally-friendly processing in the production of nutraceuticals, biofuels and bioproducts.