Center for Environmental Research and Technology and, Chemical and Environmental Engineering Department, Bourns College of Engineering, University of California, Riverside, 1084 Columbia Avenue, Riverside, CA 92507, United States.
Bioresour Technol. 2010 Dec;101(24):9624-30. doi: 10.1016/j.biortech.2010.06.137. Epub 2010 Aug 12.
Typically, the enzymatic hydrolysis rate of lignocellulosic biomass is fast initially but then slows down more rapidly than can be explained by just consumption of substrate. Although several factors including enzyme inhibition, enzyme deactivation, a drop in substrate reactivity, or nonproductive binding of enzyme to lignin could be responsible for this loss of effectiveness, we recently reported evidence that xylose, xylan, and xylooligomers dramatically decrease conversion rates and yields, but clarification was still needed for the magnitude of their effect. Therefore, in this study, xylan and various xylooligomers were added to Avicel hydrolysis at low enzyme loadings and found to have a greater effect than adding equal amounts of xylose derived from these materials or when added separately. Furthermore, xylooligomers were more inhibitory than xylan or xylose in terms of a decreased initial hydrolysis rate and a lower final glucose yield even for a low concentration of 1.67 mg/ml. At a higher concentration of 12.5mg/ml, xylooligomers lowered initial hydrolysis rates of Avicel by 82% and the final hydrolysis yield by 38%. Mixed DP xylooligomers showed strong inhibition on cellulase enzymes but not on beta-glucosidase enzymes. By tracking the profile change of xylooligomers, a large portion of the xylooligomers was found to be hydrolyzed by Spezyme CP enzyme preparations, indicating competitive inhibition by mixed xylooligomers. A comparison among glucose sugars and xylose sugars also showed that xylooligomers were more powerful inhibitors than well-established glucose and cellobiose.
通常情况下，木质纤维素生物质的酶水解速率最初很快，但随后的下降速度比仅消耗底物所解释的要快得多。尽管有几个因素，包括酶抑制、酶失活、底物反应性下降或酶与木质素的非生产性结合，可能是导致这种效力丧失的原因，但我们最近有证据表明，木糖、木聚糖和低聚木糖会显著降低转化率和产率，但仍需要澄清其影响的大小。因此，在这项研究中，在低酶负荷下向 Avicel 水解中添加木聚糖和各种低聚木糖，发现其效果比添加等量的这些材料中衍生的木糖或分别添加时更大。此外，与木聚糖或木糖相比，低聚木糖在初始水解速率降低和最终葡萄糖产率降低方面具有更大的抑制作用，即使低浓度为 1.67mg/ml。在 12.5mg/ml 的较高浓度下，低聚木糖使 Avicel 的初始水解速率降低了 82%，最终水解产率降低了 38%。混合 DP 低聚木糖对纤维素酶具有很强的抑制作用，但对β-葡萄糖苷酶没有抑制作用。通过跟踪低聚木糖的谱图变化，发现很大一部分低聚木糖被 Spezyme CP 酶制剂水解，表明混合低聚木糖存在竞争性抑制。葡萄糖糖和木糖糖的比较也表明，低聚木糖比已确立的葡萄糖和纤维二糖更具有抑制作用。
