Wallace Joshua, Brienzo Michel, García-Aparicio María P, Görgens Johann F
Department of Process Engineering, University of Stellenbosch, Private Bag X1, Stellenbosch 7602, South Africa.
Department of Process Engineering, University of Stellenbosch, Private Bag X1, Stellenbosch 7602, South Africa.
N Biotechnol. 2016 May 25;33(3):361-71. doi: 10.1016/j.nbt.2016.01.004. Epub 2016 Jan 25.
The enzymatic hydrolysis (EH) rate normally decreases during the hydrolysis, leaving unhydrolyzed material as residue. This phenomenon occurs during the hydrolysis of both cellulose (avicel) and lignocellulosic material, in nature or even pretreated. The progression of EH of steam pretreated sugarcane bagasse was associated with an initial (fast), intermediate (slower) and recalcitrant (slowest) phases, at glucan to glucose conversion yields of 61.7, 81.6 and 86%, respectively. Even though the EH of avicel as a simpler material than steam pretreated sugarcane bagasse, EH slowdown was present. The less thermo-stable endo-xylanase lost 58% of initial enzyme activity, followed by β-glucosidase that lost 16%, culminating in FPase activity loss of 30% in the first 24hours. After 72hours of EH the total loss of FPase activity was 40% compared to the initial activity. Analysis of the solid residue from EH showed that lignin content, phenolic compounds and ash increased while glucan decreased as hydrolysis progressed. During the initial fast phase of EH, the total solid residue surface area consisted predominantly of internal surface area. Thereafter, in the intermediate and recalcitrant phases of EH, the ratio of external:internal surface area increased. The proposed fiber damage and decrease in internal surface area, probably by EH action, was visualized by scanning electron microscopy imagery. The higher lignin/glucan ratio as EH progressed and enzyme deactivation by thermo instability were the main effects observed, respectively to substrate and enzyme.
酶水解（EH）速率通常在水解过程中降低，留下未水解的物质作为残余物。这种现象在纤维素（微晶纤维素）和木质纤维素材料的水解过程中都会出现，无论是在自然状态下还是经过预处理的情况下。蒸汽预处理甘蔗渣的EH进程与初始（快速）、中间（较慢）和顽固（最慢）阶段相关，葡聚糖向葡萄糖的转化率分别为61.7%、81.6%和86%。尽管微晶纤维素比蒸汽预处理甘蔗渣这种更简单的材料的EH速率较慢，但仍存在EH速率放缓的情况。热稳定性较差的内切木聚糖酶在最初24小时内丧失了58%的初始酶活性，其次是β-葡萄糖苷酶丧失了16%，最终FPase活性丧失了30%。EH 72小时后，与初始活性相比，FPase活性的总丧失率为40%。对EH固体残余物的分析表明，随着水解的进行，木质素含量、酚类化合物和灰分增加，而葡聚糖减少。在EH的初始快速阶段，总固体残余物表面积主要由内表面积组成。此后，在EH的中间和顽固阶段，外表面积与内表面积的比例增加。通过扫描电子显微镜图像可以看到，推测可能是由于EH作用导致纤维损伤和内表面积减小。随着EH的进行，较高的木质素/葡聚糖比例以及热不稳定性导致的酶失活分别是观察到的对底物和酶的主要影响。
