Microwave-assisted green solvents extraction as a sustainable approach to obtain antioxidants and enhance advanced bioethanol production from steam-exploded biomass

Achieving sustainable and economically viable bioethanol production from lignocellulosic biomass relies on efficient pre-treatments, e.g., steam explosion. However, these can generate inhibitors that hinder enzymatic hydrolysis and fermentation stages. To overcome this challenge, we explored an integrated approach combining physical extraction (microwave irradiation) with chemical solvents (green solvents) to enhance bioethanol production from steam-exploded eucalypt wood. Green solvents, such as bio-based and eutectic solvents, were essential for extracting phenolic inhibitors that can be revalorized as antioxidants. Notably, ethyl lactate emerged as the most effective extraction agent in a microwave-assisted extraction process at 100 °C for 6 min, followed by a distilled water washing step. A certain delignification effect was also observed. After separate hydrolysis and fermentation process of the extracted sample, a maximum bioethanol production of 15.7 ± 0.3 g/L was achieved compared to 12.7 ± 0.0 g/L for the control sample. In addition, the samples were characterised through chemical composition and FTIR analysis. Overall, this study marks a significant advancement in producing environmentally friendly biofuels by integrating innovative extraction techniques with green solvents. This opens new possibilities for second-generation biofuels. At the same time, valuable by-products like antioxidants contribute to the broader goal of making bioethanol production economically feasible.