Cellulase digestibility of pretreated biomass is limited by cellulose accessibility
Cellulase digestibility of pretreated biomass is limited by cellulose accessibility
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DOI：
10.1002/bit.21408
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发表时间：
2007-09-01
影响因子：
3.8
通讯作者：
Johnson, David K.
中科院分区：
文献类型：
--
作者：
Jeoh, Tina;Ishizawa, Claudia I.;Johnson, David K.
试图将生物质的物理和化学性质与其对酶消化的敏感性相关联通常是不确定的或矛盾的，这取决于诸如底物类型、预处理条件和测量技术等变量。在这项研究中，我们提出了一种直接方法，通过使用来自里氏木霉的纯化纤维二糖水解酶（Cel 7A）直接探测纤维素酶结合和活性来测量控制生物质样品中纤维素消化率的关键因素。标记T. reesei Cel7A用于测定预处理的玉米秸秆样品和纯纤维素底物，以鉴定纤维素酶制剂的这一重要组分的可接近性的障碍。结果表明，T. reesei Cel7A以较高浓度结合，表明该酶更容易接近底物。发现预处理程度、预处理后的干燥和纤维素结晶度等因素直接影响酶的可及性。这项研究提供了直接的证据来支持这样的观点，即使生物质更容易被纤维二糖水解酶消化的最佳预处理方案是那些改善生物质细胞壁中纤维素的获得的方案，以及那些能够降低细胞壁纤维素的结晶度的方案。
Attempts to correlate the physical and chemical properties of biomass to its susceptibility to enzyme digestion are often inconclusive or contradictory depending on variables such as the type of substrate, the pretreatment conditions and measurement techniques. In this study, we present a direct method for measuring the key factors governing cellulose digestibility in a biomass sample by directly probing cellulase binding and activity using a purified cellobiohydrolase (Cel7A) from Trichoderma reesei. Fluorescence-labeled T. reesei Cel7A was used to assay pretreated corn stover samples and pure cellulosic substrates to identify barriers to accessibility by this important component of cellulase preparations. The results showed cellulose conversion improved when T. reesei Cel7A bound in higher concentrations, indicating that the enzyme had greater access to the substrate. Factors such as the pretreatment severity, drying after pretreatment, and cellulose crystallinity were found to directly impact enzyme accessibility. This study provides direct evidence to support the notion that the best pretreatment schemes for rendering biomass more digestible to cellobiohydrolase enzymes are those that improve access to the cellulose in biomass cell walls, as well as those able to reduce the crystallinity of cell wall cellulose.