Current Pretreatment Technologies for the Development of Cellulosic Ethanol and Biorefineries
Current Pretreatment Technologies for the Development of Cellulosic Ethanol and Biorefineries
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DOI：
10.1002/chin.201550242
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发表时间：
2015-12
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通讯作者：
M. H. L. Silveira;A. Morais;A. Lopes;Drielly N Olekszyszen;R. Bogel-Lukasik;J. Andreaus;L. Ramos
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文献类型：
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作者：
M. H. L. Silveira;A. Morais;A. Lopes;Drielly N Olekszyszen;R. Bogel-Lukasik;J. Andreaus;L. Ramos
木质纤维材料，如森林、农业和农用工业残渣，是生物炼油厂提供燃料、化学品和材料的最重要资源之一，至少部分取代了石油化学在现代社会中的作用。这些可持续的生物精炼产品大多可以从植物多糖(葡聚糖、半纤维素、淀粉和果胶物质)和木质素中生产出来。在这种情况下，几十年来，纤维素乙醇一直被认为是最有希望的替代方案之一，以减轻对化石燃料的依赖和大气中二氧化碳的积累。然而，需要一种前处理方法来克服木质素-碳水化合物复合材料中存在的物理和化学障碍，并使大多数(如果不是全部)植物细胞壁成分易于转化为有价值的产品，包括燃料乙醇。因此，预处理是经济上可行的生物炼油厂的关键步骤。成功的前处理方法必须部分或全部分离木质纤维组分，增加综纤维素对酶解的可及性，并为后续的酶解和发酵步骤释放抑制作用最小的化合物。每种前处理技术对碳水化合物和木质素都有不同的特异性，对于不同类型的生物质可能有效，也可能无效。此外，还需要开发使用更环保的化学品和对环境影响较小的流出物的前处理方法。本文概述了现有的最重要的前处理方法，包括基于使用绿色溶剂(超临界流体和离子液体)的方法。
Lignocellulosic materials, such as forest, agriculture, and agroindustrial residues, are among the most important resources for biorefineries to provide fuels, chemicals, and materials in such a way to substitute for, at least in part, the role of petrochemistry in modern society. Most of these sustainable biorefinery products can be produced from plant polysaccharides (glucans, hemicelluloses, starch, and pectic materials) and lignin. In this scenario, cellulosic ethanol has been considered for decades as one of the most promising alternatives to mitigate fossil fuel dependence and carbon dioxide accumulation in the atmosphere. However, a pretreatment method is required to overcome the physical and chemical barriers that exist in the lignin–carbohydrate composite and to render most, if not all, of the plant cell wall components easily available for conversion into valuable products, including the fuel ethanol. Hence, pretreatment is a key step for an economically viable biorefinery. Successful pretreatment method must lead to partial or total separation of the lignocellulosic components, increasing the accessibility of holocellulose to enzymatic hydrolysis with the least inhibitory compounds being released for subsequent steps of enzymatic hydrolysis and fermentation. Each pretreatment technology has a different specificity against both carbohydrates and lignin and may or may not be efficient for different types of biomasses. Furthermore, it is also desirable to develop pretreatment methods with chemicals that are greener and effluent streams that have a lower impact on the environment. This paper provides an overview of the most important pretreatment methods available, including those that are based on the use of green solvents (supercritical fluids and ionic liquids).