Hydrolysis Assessment of Orange Peel and Brewer’s Spent Grain for Bioethanol Production

Bioethanol is a promising alternative to fossil fuels. This study evaluated bioethanol production from orange peel (OP) and brewer’s spent grain (BSG) through acid hydrolysis, followed by fermentation with Saccharomyces cerevisiae. A factorial design was applied to assess the influence of temperature, acid concentration, and time on sugar release. Hydrolysis of OP at 125 °C with 0.5% H2SO4 yielded 52.14 g/L of glucose and 15.70 g/L of xylose. For BSG, the best results were obtained with 2.5% H2SO4 at 160 °C, producing 27.10 g/L of glucose and 14.22 g/L of xylose. Fermentation at 30 °C achieved 5.25% v/v bioethanol in OP and 1.5% v/v in BSG, representing 41.4 g/L and 11.8 g/L of bioethanol, respectively. The kinetic models showed high predictive accuracy (R2 > 0.98). These findings demonstrate the potential of OP and BSG as viable substrates for bioethanol production under mild processing conditions.