Organosolv and Hydrothermal Pretreatments of Sugarcane Bagasse and Straw and Enzymatic Hydrolysis of Hemicellulosic Liquor

The global demand for sustainable energy has accelerated the development of biofuels, aiming to reduce fossil fuel reliance and environmental impact. Second-generation ethanol (2G), produced from lignocellulosic biomass such as sugarcane bagasse and straw, is a promising alternative aligned with the circular economy. Its production relies on pretreatments to improve the enzymatic access to polysaccharides. Among the available methods, the organosolv (O) and hydrothermal (H) pretreatments are effective in separating the biomass into cellulose-rich pulps and hemicellulosic liquors. In this study, these pretreatments were applied to sugarcane bagasse (SCB) and straw (SS), aiming to obtain hemicellulosic fractions for bioconversion. The characterization of pretreated biomasses showed increased cellulose content, indicating successful delignification. After the lignin precipitation, the hemicellulosic liquors were submitted to enzymatic hydrolysis, with increases in the total reducing sugar (TRS) concentrations, from 11.144 to 13.440 g·L−1 (SBO), 16.507 to 22.492 g·L−1 (SBH), 8.560 to 9.478 g·L−1 (SSO), and 14.164 to 22.830 g·L−1 (SSH), with highlights for the hydrothermal pretreated hydrolysates in the improvement of sugar release. HPLC confirmed these gains, notably in the xylose content. The results indicated the potential of hemicellulosic liquors for the fermentation of pentoses, supporting integrated bioethanol production. This approach promotes the efficient use of agro-residues and strengthens the role of biofuels in low-carbon and sustainable energy systems.