Innovation Center of Efficient Processing and Utilization of Forest Resources, College of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, China.
State Key Laboratory of Pulp Paper Engineering, South China University of Technology, Guangzhou 510640, China.
Int J Mol Sci. 2022 Oct 5;23(19):11829. doi: 10.3390/ijms231911829.
Hydrothermal pretreatment (HTP) has long been considered as an efficient and green treatment process on lignocellulosic biomass for bioconversion. However, the variations of cellulose supramolecular structures during HTP as well as their effects on subsequent enzymatic conversion are less understood. In this work, bamboo holocellulose with well-connected cellulose and hemicelluloses polysaccharides were hydrothermally treated under various temperatures. Chemical, morphological, and crystal structural determinations were performed systematically by a series of advanced characterizations. Xylan was degraded to xylooligosaccharides in the hydrolyzates accompanied by the reduced degree of polymerization for cellulose. Cellulose crystallites were found to swell anisotropically, despite the limited decrystallization by HTP. Hydrogen bond linkages between cellulose molecular chains were weakened due to above chemical and crystal variations, which therefore swelled, loosened, and separated the condensed cellulose microfibrils. Samples after HTP present notably increased surface area, favoring the adsorption and subsequent hydrolysis by cellulase enzymes. A satisfying enzymatic conversion yield (>85%) at rather low cellulase enzyme dosage (10 FPU/g glucan) was obtained, which would indicate new understandings on the green and efficient bioconversion process on lignocellulosic biomass.
水热预处理（HTP）长期以来被认为是一种有效的绿色处理工艺，用于木质纤维素生物质的生物转化。然而，纤维素超分子结构在 HTP 过程中的变化及其对后续酶转化的影响还不太清楚。在这项工作中，采用不同温度对具有良好连接的纤维素和半纤维素多糖的竹原纤维进行了水热预处理。通过一系列先进的表征，系统地进行了化学、形态和晶体结构的测定。木聚糖在水解产物中降解为木二糖，同时纤维素的聚合度降低。尽管 HTP 的结晶度降低有限，但纤维素晶须仍表现出各向异性的溶胀。由于上述化学和晶体变化，纤维素分子链之间的氢键连接减弱，导致纤维素微纤维凝聚膨胀、疏松和分离。经过 HTP 的样品具有显著增加的表面积，有利于纤维素酶的吸附和随后的水解。在较低的纤维素酶用量（10 FPU/g 葡萄糖）下，可获得令人满意的酶转化收率（>85%），这将为木质纤维素生物质的绿色、高效生物转化过程提供新的认识。
