Acid Hydrothermal Amendment of Grape Wine Pomace: Enhancement of Phenol and Carbohydrate Co-Solubilization

Abstract

Byproducts from the winery industry contain many bioactive compounds that are considered high-value-added compounds. White grape pomace (GP) is rich in carbohydrates; consequently, it can be used as a raw material for subsequent bioprocesses. In the present study, low-temperature hydrothermal treatments were carried out using different operational conditions regarding temperature (65–95 °C), time (120–240 min), and sulfuric acid addition at various concentrations (5–15% v/v). The results showed that by using a temperature of 65 °C, a period of 120 min, and 15% (v/v) of H2SO4, it was possible to obtain a liquid phase rich in phenols and carbohydrates, with total phenol compounds corresponding to 2113 ± 140 mg of gallic acid/kg GP and composed mainly of 3-hydroxytyrosol (1330 ± 22 mg/kg GP). In parallel, carbohydrate solubilization reached 245 g glucose/kg GP. These results demonstrate the promising potential of hydrothermally treated grape pomace as raw material for biorefinery processes.

Optimisation of the biological production of levulinic acid in a mixed microbial culture fed with synthetic grape pomace

“…We collected 10 L of aerobic sludge from the recirculation line on the aerobic reactor and let it settle for 12 h. In addition, 1.5 L of concentrated aerobic sludge was taken and used as inoculum. To ensure the reproducibility of the experiments, a synthetic GP hydrolysate was prepared based on the sugar composition previously reported by Serrano et al (2023), i.e., 64% glucose, 31% xylose and 5% arabinose. Using a synthetic mixture made it possible to circumvent undesirable interferences in the evaluation of the suitability of the sugar mixture as a substrate for LA accumulation.…”