USDA Forest Service, Forest Products Laboratory, Madison, WI, USA.
Department of Biomedical Engineering, Jinan University, Guangzhou, P. R. China.
ChemSusChem. 2021 Aug 9;14(15):3031-3046. doi: 10.1002/cssc.202100915. Epub 2021 Jul 14.
This Minireview provides a comprehensive discussion on the potential of using acid hydrotropes for sustainably fractionating lignocelluloses for biorefinery applications. Acid hydrotropes are a class of acids that have hydrotrope properties toward lignin, which helps to solubilize lignin in aqueous systems. With the capability of cleaving ether and ester bonds and even lignin-carbohydrate complex (LCC) linkages, these acid hydrotropes can therefore isolate lignin embedded in the plant biomass cell wall and subsequently solubilize the isolated lignin in aqueous systems. Performances of two acid hydrotropes, that is, an aromatic sulfonic acid [p-toluenesulfonic acid (p-TsOH)] and a dicarboxylic acid [maleic acid (MA)], in terms of delignification and dissolution of hemicelluloses, and reducing lignin condensation, were evaluated and compared. The advantages of lignin esterification by MA for producing cellulosic sugars through enzymatic hydrolysis and lignin-containing cellulose nanofibrils (LCNFs) through mechanical fibrillation from the fractionated water insoluble solids (WIS), and for obtaining less condensed lignin with light color, were demonstrated. The excellent enzymatic digestibility of maleic acid hydrotropic fractionation WISs was also demonstrated by comparing with WISs from other fractionation processes. The recyclability and reusability of acid hydrotropes were also reviewed. Finally, perspectives on future research needs to address key technical issues for commercialization were also provided.
这篇综述全面讨论了利用酸水增溶剂可持续地将木质纤维素分级用于生物炼制应用的潜力。酸水增溶剂是一类具有木质素增溶性能的酸，有助于在水相体系中溶解木质素。这些酸水增溶剂能够切断醚键和酯键，甚至木质素-碳水化合物复合物（LCC）键，因此可以分离嵌入植物生物质细胞壁中的木质素，并随后将分离出的木质素溶解在水相体系中。评估并比较了两种酸水增溶剂，即芳香族磺酸（对甲苯磺酸（p-TsOH））和二羧酸（马来酸（MA））在脱木质素和溶解半纤维素、降低木质素缩合方面的性能。展示了 MA 对木质素进行酯化的优势，可通过酶水解生产纤维素糖，并通过机械纤化从分级后的不溶性固体（WIS）中获得含有木质素的纤维素纳米纤维（LCNF），并获得颜色较浅、缩合程度较低的木质素。通过与其他分级过程的 WIS 进行比较，还证明了马来酸水增溶分级 WIS 具有优异的酶可消化性。还综述了酸水增溶剂的可回收性和再利用性。最后，还就未来研究需要解决商业化的关键技术问题提供了展望。
