Effect of Pretreatment of Orange Peel with Deep Eutectic Solvents Before Acid Hydrolysis to Produce Reduced Sugars

Currently, approximately 80% of the energy used worldwide comes from fossil fuels. The production of bioethanol from agro-industrial waste requires pretreatment due to the latter’s rigid structure and resistance to degradation. In this work orange peel (OP) was pretreated with deep eutectic solvents (DESs), varying the molar ratio of the mixture to delignify the OP, exposing cellulose and hemicellulose, in order to improve the yield in the acid hydrolysis process with H3PO4 to produce reduced sugars. SEM, FTIR, and XRD were used to evaluate the structural changes in OP with and without pretreatment. Optimal pretreatment was achieved using ChCl/U at a 1:4 molar ratio, yielding 31.58 g of reducing sugars per 100 g of pretreated OP after 150 min, compared with 12.09 g of reducing sugars per 100 g of untreated OP after 300 min. The holocellulose content after pretreatment increased by 28%. Significant differences were found in the reducing-sugar yield and the structure of OP with and without pretreatment; DESs are useful for biomass delignification, thus enabling increased reducing-sugar production through acid hydrolysis.