Dept. of Chemical Engineering, University of New Brunswick, Fredericton, NB, Canada.
Biotechnol Prog. 2012 Nov-Dec;28(6):1389-99. doi: 10.1002/btpr.1613. Epub 2012 Sep 27.
Cell wall deterioration throughout enzymatic hydrolysis of cellulosic biomass is greatly affected by the chemical composition and the ultrastructure of the fiber cell wall. The resulting pattern of cell wall deterioration will reveal information on cellulose activity throughout enzymatic hydrolysis. This study investigates the progression and morphological changes in lignocellulose fibers throughout enzymatic hydrolysis, using (transmission electron microscopy) TEM and field emission scanning electron microscopy (FE-SEM). Softwood thermo-mechanical pulp (STMP) and softwood bleached kraft pulp (SBKP), lignocellulose substrates containing almost all the original fiber composition, and with lignin and some hemicellulose removed, respectively, was compared for morphology changes throughout hydrolysis. The difference of conversion between STMP and SBKP after 48 h of enzymatic hydrolysis is 11 and 88%, respectively. TEM images revealed an even fiber cell wall cross section density, with uneven middle lamella coverage in STMP fibers. SKBP fibers exhibited some spaces between cell wall and lamella layers due to the removal of lignin and some hemicellulose. After 1 h hydrolysis in SBKP fibers, there were more changes in the fiber cross-sectional area than after 10 h hydrolysis in STMP fibers. Cell wall degradation was uneven, and originated in accessible cellulose throughout the fiber cell wall. FE-SEM images illustrated more morphology changes in SBKP fibers than STMP fibers. Enzymatic action of STMP fiber resulted in a smoother fiber surface, along with fiber peeling and the formation of ribbon-disjunction layers. SBKP fibers exhibited structural changes such as fiber erosion, fiber cutting, and fiber splitting throughout enzymatic hydrolysis.
细胞壁在纤维素生物质的酶解过程中的劣化受到纤维细胞壁的化学成分和超微结构的极大影响。细胞壁劣化的结果模式将揭示纤维素在整个酶解过程中的活性信息。本研究使用（透射电子显微镜）TEM 和场发射扫描电子显微镜（FE-SEM）研究木质纤维素纤维在酶解过程中的进展和形态变化。比较了软木热机械浆（STMP）和软木漂白硫酸盐浆（SBKP），这两种木质纤维素底物几乎都保留了原始纤维成分，分别去除了木质素和一些半纤维素，以研究水解过程中的形态变化。48 小时酶解后 STMP 和 SBKP 的转化率差异分别为 11%和 88%。TEM 图像显示，STMP 纤维的纤维细胞壁横截面密度均匀，中层片覆盖不均匀。由于木质素和一些半纤维素的去除，SBKP 纤维的细胞壁和层片之间有一些空间。在 SBKP 纤维中水解 1 小时后，纤维横截面面积的变化比在 STMP 纤维中水解 10 小时后更大。细胞壁降解不均匀，起源于整个纤维细胞壁中的可及纤维素。FE-SEM 图像表明，SBKP 纤维的形态变化比 STMP 纤维更多。STMP 纤维的酶作用导致纤维表面更光滑，同时纤维剥落和形成带状分离层。SBKP 纤维在整个酶解过程中表现出结构变化，如纤维侵蚀、纤维切割和纤维分裂。
