Abstract

Pretreatment to enhance the enzymatic digestibility of cellulose usually alters the structure of lignin, resulting in subsequent inferior depolymerization and utilization. Herein, a physicochemical pretreatment strategy, specifically, using a recyclable acid hydrotrope (p-toluenesulfonic acid, p-TsOH) followed by 10 s of ultrasonic treatment, was developed to facilitate high-value lignin extraction from lignocellulosic biomass and improve enzymatic hydrolysis for high-titer ethanol production. The wood material (poplar) was first treated with the recyclable p-TsOH aqueous solution under mild conditions (C80T80t15) to extract the lignin. The obtained lignin exhibited excellent properties, including a high hydroxyl (OH) content (4.19 and 4.07 mmol/g of aliphatic and phenolic OH, respectively), abundant β-O-4 aryl ether linkages (60%), a low M_w (3357 ± 121 g/mol), and a narrow polydispersity (2.28, M_w/M_n), according to the results from FTIR spectroscopy, TGA, ³¹P NMR spectroscopy, 2D-HSQC NMR spectroscopy, and GPC. The pretreated substrates were then subjected to 10 s of ultrasonication to improve the enzymatic saccharification and finally afford ethanol by quasi-simultaneous enzymatic saccharification and fermentation (Q-SSF). The highest ethanol concentration (40.08 ± 3 g/L) was obtained after 60 h of fermentation, and the residual glucose concentration was only 4.22 ± 1 g/L; this experimental ethanol yield was equivalent to the theoretical ethanol yield of 81.87 ± 4% based on the glucan content. In short, this pretreatment method simultaneously enhanced the accessibility of cellulose to enzymatic hydrolysis and provided high-value lignin.

Graphic abstract

中文翻译：

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使用可循环酸水溶助长剂和随后的短期超声预处理以促进高价值木质素提取和高滴度乙醇生产

摘要

增强纤维素酶消化率的预处理通常会改变木质素的结构，从而导致随后的解聚和利用不良。这里，物理化学预处理策略，具体地，使用一个可回收酸水溶助长剂（p -甲苯磺酸，p -TsOH），接着10秒超声处理的，被开发用于从木质纤维素生物质促进高价值的木质素提取和改进高酶促水解-滴定乙醇生产。木材（杨树）首先用可回收的p处理。-TsOH水溶液在温和的条件下（C80T80t15）提取木质素。所获得的木质素显示出优异的性能，包括高的羟基（OH）含量（分别为4.19和4.07 mmol / g的脂肪族和酚式OH），丰富的β-O-4芳基醚键（60％），低的M _w（根据FTIR光谱法（TGA）³¹的结果，其分子量为3357±121 g / mol）和窄的多分散性（2.28，M _w / M _n）。P NMR光谱，2D-HSQC NMR光谱和GPC。然后将预处理的底物进行10秒钟的超声处理，以改善酶促糖化作用，并最终通过准同时酶促糖化和发酵（Q-SSF）提供乙醇。发酵60 h后获得最高乙醇浓度（40.08±3 g / L），残留葡萄糖浓度仅为4.22±1 g / L。该实验乙醇收率相当于基于葡聚糖含量的理论乙醇收率81.87±4％。简而言之，该预处理方法同时提高了纤维素酶促水解的可及性，并提供了高价值的木质素。

图形摘要