木质纤维素预处理技术研究进展

Research progress on lignocellulose pretreatment technology

木质纤维素转化燃料乙醇一般需要经过原料预处理、酶水解和发酵过程。由于木质纤维原料化学结构复杂、直接酶解效率非常低,一般在酶水解之前需要进行适当的预处理以打破其致密结构,增加纤维表面积,提高后续纤维素酶的可及性。预处理程度直接影响纤维底物后续酶水解的效果。本文在木质纤维素常用预处理技术分析的基础上,重点讨论了3种相对高效的预处理技术:微波辅助离子液体预处理、两阶段深度共熔溶剂(D ES)预处理和氯化铁预处理技术,分析了它们的优势、不足及发展现状。文中指出微波辅助离子液体预处理可有效解构木质素和半纤维素,破坏纤维素结晶区域,利于后续酶解,但微波加热过程会使离子液体分解和部分底物碳化。两阶段DES预处理可有效提高酶水解效率,但是预处理后原料中残留的DES可能会对后续反应中纤维素酶和微生物产生抑制作用。氯化铁预处理可有效破坏木质素与碳水化合物间的结合键,脱除底物中的半纤维素,而对木质素和纤维素降解较少,具有很好的发展前景。由于单一预处理技术的局限性,寻求低成本高效的联合预处理技术将是未来重点发展的方向。

Fuel ethanol conversion by lignocellulose generally requires raw materials pretreatment,enzymatic hydrolysis and fermentation processes.The efficiency of direct enzymatic hydrolysis of cellulosic biomass is very low due to the complex chemical structure of the lignocellulosic materials.Generally,appropriate pretreatment is necessary before enzymatic hydrolysis is carried out in order to break the dense structure of substrate,increase the surface area of the cellulose and improve the subsequent cellulase accessibility.Based on the analysis of common pretreatment techniques for lignocellulose,this paper focused on three relatively efficient pretreatment techniques:microwaveassisted ionic liquid pretreatment,two-stage deep eutectic solvents pretreatment and FeCl3 pretreatment.Their strengths and weaknesses were analyzed.Microwave-assisted ionic liquid pretreatment can effectively deconstruct lignin and hemicellulose,destroy the crystalline region of cellulose,and facilitate subsequent enzymatic hydrolysis.However,microwave heating process will decompose ionic liquid and carbonize some substrates,which will reduce the effect of pretreatment.Two-stage DES pretreatment can effectively improve the enzymatic hydrolysis efficiency,but the residual DES in the raw material after pretreatment may inhibit the cellulase and microorganisms in the subsequent reaction.FeCl3 pretreatment can effectively destroy the ether bond and partial ester bond between lignin and carbohydrate,and remove hemicellulose from the substrate,while less degradation of lignin and cellulose.Finally,the paper prospected the development trend of lignocellulose pretreatment technology.