Deep eutectic solvent (DES) has been tipped as an upcoming green solvent in biomass processing. In this study, choline-based DES was facilely synthesized and applied for the valorization of banana peel waste. The as-prepared DES shows an excellent performance in the pretreatment of banana peel waste by removing amorphous part of lignin and hemicellulose content as confirmed by SEM, XRD, and FT-IR analysis. Optimization of hydrolysis parameters over heterogeneous catalyst including reaction temperature, catalyst dosage, biomass loading, and reaction time was investigated to attain maximum of 72.9% of TRS yield. The functional moieties such as –SO₃H, phenolic –OH, and –COOH groups on the surface of the catalyst play a vital role in the conversion of pretreated banana peel waste to reducing sugars by breaking the cleavage of glycosidic bonds into monomeric sugars. The catalytic hydrolysate was then fermented into bioethanol using Saccharomyces cerevisiae (baker’s yeast) and the presence of ethanol was confirmed with potassium dichromate method. As a result, DES pretreatment of lignocellulosic biomass will be effective with the combination of catalytic hydrolysis for the production of biofuel.

Graphical abstract

Choline-based deep eutectic solvent effectively deconstructs the complex structure of banana peel waste by reducing amorphous lignin and hemicelluloses, while cellulose remains intact. And also, utilization of MCAC favors the hydrolysis process by cleaving the glycosidic linkages on polysaccharides into maximum yield of monomers. The catalytic hydrolysate can produce biofuel via microbial fermentation.

中文翻译：

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在用于生物乙醇生产的多相催化剂上使用 DES 预处理和水解使水果废物增值

深共熔溶剂 (DES) 已被认为是生物质加工中即将到来的绿色溶剂。在这项研究中，基于胆碱的 DES 被轻松合成并应用于香蕉皮废物的增值。通过 SEM、XRD 和 FT-IR 分析证实，所制备的 DES 通过去除木质素的无定形部分和半纤维素含量，在香蕉皮废料的预处理中表现出优异的性能。研究了多相催化剂上水解参数的优化，包括反应温度、催化剂用量、生物质负载和反应时间，以获得最大 72.9% 的 TRS 产率。-SO ₃等功能性部分催化剂表面的 H、酚类 -OH 和 -COOH 基团通过将糖苷键断裂成单糖，在将预处理过的香蕉皮废料转化为还原糖方面发挥着至关重要的作用。然后使用酿酒酵母（面包酵母）将催化水解产物发酵成生物乙醇，并用重铬酸钾法确认乙醇的存在。因此，木质纤维素生物质的 DES 预处理与催化水解相结合将有效地生产生物燃料。

图形概要

基于胆碱的低共熔溶剂通过减少无定形木质素和半纤维素，有效地解构香蕉皮废料的复杂结构，同时纤维素保持完整。而且，MCAC 的利用有利于水解过程，通过将多糖上的糖苷键切割成最大产量的单体。催化水解产物可通过微生物发酵生产生物燃料。