In order to confirm the contribution of delignification to the increase in lignocellulosic cellulose digestibility, several laboratory oxidative pretreatments under mild conditions, including alkaline-hydrogen peroxide (AP), two-step alkaline/peracetic acid (APAA) and sodium chlorite (SC) pretreatments were employed to achieve selective delignification of sugarcane bagasse and retained most of the hemicelluloses (xylan) in the pretreated solids. Four commercial cellulase cocktails were used to test the enzymatic hydrolyzability of pretreated substrates. Results revealed that delignification indeed could greatly improve the final (120 h) cellulose hydrolysis with relatively high final (120 h) glucan conversion (> 90%) by different cellulase cocktails even if the substrates still had a high hemicelluloses content. However, the xylan conversion seemed to be more greatly dependent on the pretreatments and cellulase cocktails used. AP and APAA pretreatments resulted in the disappearance of middle lamella and liberation of cellulose fibers with significant etching, deformation and fracture of cell wall structure. SC pretreatment greatly modified the sugar bagasse surface morphology to make the surface much coarser. The cell wall also underwent serious fracture and deformation with some middle lamella disappearing. However, no significant alteration on the structure of pure cellulose was observed by SC oxidative pretreatment of filter paper. Oxidative pretreatment might also modify lignin structure and surface properties thus greatly reducing the non-specific adsorption of enzymes. The obtained results strongly support the conclusion that delignification under mild pretreatment condition can be very helpful to improve the enzymatic hydrolysis of lignocellulosic cellulose by commercial cellulase cocktails even if the substrates has a high hemicelluloses content.

中文翻译：

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比较不同氧化预处理对多糖水解能力和细胞壁结构的影响，以解释通过脱木素作用大大提高甘蔗渣的酶消化率

为了确认脱木素作用对木质纤维素纤维素消化率增加的影响，在温和条件下进行了几种实验室氧化预处理，包括碱性过氧化氢（AP），两步式碱/过乙酸（APAA）和亚氯酸钠（SC）预处理将其用于实现甘蔗渣的选择性脱木质素并在预处理的固体中保留大部分半纤维素（木聚糖）。四种市售纤维素酶混合物用于测试预处理底物的酶水解能力。结果表明，即使底物仍具有高半纤维素含量，脱木质素的确可以通过不同的纤维素酶混合物极大地改善最终（120 h）纤维素的水解，并具有相对较高的最终（120 h）葡聚糖转化率（> 90％）。然而，木聚糖转化似乎很大程度上取决于预处理和所用的纤维素酶混合物。AP和APAA预处理导致中间层的消失和纤维素纤维的释放，并具有明显的蚀刻，变形和细胞壁结构破裂。SC预处理极大地改变了蔗糖蔗糖的表面形态，使其表面更加粗糙。细胞壁也经历了严重的断裂和变形，其中一些中间层消失了。然而，滤纸的SC氧化预处理未观察到纯纤维素结构的显着变化。氧化预处理也可能会改变木质素的结构和表面性质，从而大大减少酶的非特异性吸附。