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The effects of surfactant pretreatment and xylooligomers on enzymatic hydrolysis of cellulose and pretreated biomass.

机译：表面活性剂预处理和低聚木二聚体对纤维素和预处理生物质的酶促水解的影响。

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摘要

There is a vital need to reduce enzyme costs to facilitate production of cost-competitive cellulosic ethanol and other products. End-product inhibition, declining substrate reactivity, enzyme denaturation, and non-productive binding of enzyme to lignin are among the factors that could account for the loss of enzyme effectiveness as enzymatic hydrolysis of lignocellulosic biomass proceeds. In addition, lignin and hemicelluloses, the other two most abundant components in lignocellulosic biomass besides cellulose, are believed to be responsible for high recalcitrance of lignocellulosic biomass to biological conversion. This study focused on investigating the effects of hemicelluloses on enzymatic hydrolysis and developing possible strategies to overcome their negative impacts. In the first part of the study, we identified that xylooligomers released from biomass during pretreatment and enzymatic hydrolysis are stronger inhibitors than long known for glucose and cellobiose. Furthermore, mixtures of xylooligomers of varying chain length were shown to dramatically decrease enzymatic conversion rates and yields of both pure cellulose and pretreated biomass. To clarify the relative importance of different xylooligomers, gel permeation chromatography (GPC) was applied to separate xylooligomers according to their chain length, and selected fractions were added to pure cellulose hydrolysis to determine their relative influence on rates and yields. The degree of inhibition was found to increase with xylooligomer degree of polymerization (DP), and cellulase exhibited a greater binding affinity for birchwood xylan than pure cellulose. All of these observations suggest that xylooligomers could competitively adsorb on cellulase, thereby reducing enzyme accessibility to cellulose and cellooligomers. Consequently, applying hemicellulase to hydrolyze xylooligomers to much less inhibitory xylose prior to adding cellulase reduced this undesirable binding and was more beneficial than adding hemicellulase and cellulase together.
机译：迫切需要降低酶的成本，以促进具有成本竞争力的纤维素乙醇和其他产品的生产。最终产物的抑制，底物反应性的下降，酶的变性以及酶与木质素的非生产性结合都是可以解释随着木质纤维素生物质的酶促水解而导致酶效力下降的因素。另外，木质素和半纤维素是木质纤维素生物质中除纤维素之外的另外两个最丰富的组分，被认为是木质纤维素生物质向生物转化的高抵抗性的原因。这项研究专注于研究半纤维素对酶促水解的影响，并开发克服其负面影响的可能策略。在研究的第一部分中，我们确定了预处理和酶促水解过程中从生物质中释放的低聚木二糖是比长期以来对葡萄糖和纤维二糖已知的抑制剂更强的抑制剂。此外，显示出不同链长的二甲苯基低聚物的混合物显着降低了酶转化率以及纯纤维素和预处理生物质的产率。为了阐明不同的低聚木二聚体的相对重要性，将凝胶渗透色谱法（GPC）根据其链长应用于分离的低聚木二聚体，并将选定的级分添加到纯纤维素水解中，以确定它们对速率和产率的相对影响。发现抑制程度随着木寡聚体聚合度（DP）的增加而增加，并且纤维素酶对桦木木聚糖表现出比纯纤维素更大的结合亲和力。所有这些观察结果表明，低聚木二聚体可以竞争性地吸附在纤维素酶上，从而降低了纤维素和纤维素低聚体的酶可及性。因此，在添加纤维素酶之前，应用半纤维素酶将木糖寡聚体水解成抑制性较小的木糖可以减少这种不希望的结合，并且比将半纤维素酶和纤维素酶一起添加更有益。

著录项

  • 作者

    Qing, Qing.;

  • 作者单位

    University of California, Riverside.;

  • 授予单位 University of California, Riverside.;
  • 学科 Chemistry Biochemistry.;Engineering Chemical.
  • 学位 Ph.D.
  • 年度 2010
  • 页码 263 p.
  • 总页数 263
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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