Oil palm frond (OPF) is one of the most abundant lignocellulosic biomass wastes found in the palm oil industry. However, the recalcitrant nature of OPF makes it hard to produce reducing sugar and convert it into subsequent high-value chemicals. Therefore, OPF was subjected to an ultrasound-assisted NaOH-aqueous deep eutectic solvent (DES) pretreatment in this study to increase delignification and enhance enzymatic saccharification. The effects of ultrasonication on the combined NaOH-aqueous DES for OPF pretreatment and saccharification were scrutinized. Under the recommended ultrasonic pretreatment (amplitude 60 %, duration 30 min) with 2.5 % NaOH-aqueous DES, lignin removal was significantly improved to 47.00 % in comparison to that obtained without ultrasound pretreatment, 30.92 %. OPF subjected to the recommended pretreatment was able to retain a high polysaccharide content, where subsequent enzymatic saccharification was able to achieve a glucose yield of 90.12 %. Physical and chemical characterizations of pretreated OPF were carried out to provide evidence to explain the observed improvement in lignin removal and enzymatic hydrolysis. The use of NaOH-aqueous DES as an ultrasonic medium was proven to be an effective method to promote a novel one-pot, two-processes pretreatment system.

油棕叶（OPF）是在棕榈油工业中发现的最丰富的木质纤维素生物质废物之一。然而，OPF的顽强特性使其很难产生还原糖并将其转化为后续的高价值化学品。因此，本研究对OPF进行了超声辅助的NaOH水溶液深共晶溶剂（DES）预处理，以增加去木质素和增强酶促糖化作用。考察了超声处理对NaOH水溶液DES进行OPF预处理和糖化的影响。在推荐的超声预处理（振幅60％，持续时间30分钟）中，使用2.5％NaOH水溶液DES，与未进行超声预处理（30.92％）相比，木质素去除率显着提高至47.00％。经过推荐的预处理的OPF能够保留较高的多糖含量，随后的酶促糖化作用可实现90.12％的葡萄糖产率。进行了预处理OPF的物理和化学表征，以提供证据来说明观察到的木质素去除和酶促水解方面的改进。实践证明，使用NaOH水溶液DES作为超声介质是推广新型一锅两步预处理系统的有效方法。