Enhancing the enzymatic degradation of lignocellulosic biomass

化石燃料是世界各地能源和碳基化学品的主要来源，但其使用是不可持续的。木质纤维素生物质是产生燃料和原材料的一种“更绿色”的替代来源。这种生物质的破坏以获得用于生物燃料的纤维素和半纤维素导致几乎没有价值的木质素废物，其构成初始植物生物质的15-30%，但是木质素（植物的“木质”部分）也是可再生底物和芳香族单体的潜在来源。在自然环境中，微生物使用酶如漆酶和过氧化物酶分解生物质中的木质素1。本项目将利用模型木质素和废弃木质素研究此类酶降解木质素的酶促过程，旨在提高和工业化该过程。如果要在从这种丰富和可持续的碳原料中获得价值方面取得进展，对木质素结构的分析仍然是必不可少的。例如，目前分子量的测定，通常通过凝胶渗透色谱法使用聚苯乙烯标准物进行，证明是不够的。有必要改进分析，特别是在按此处计划与降解实验同时进行时。被选中的博士生将使用SEM，FT-IR和FT-ICR MS等技术来建立我们对现成的木质素废物，Organosolv和Kraft木质素的详细分析。圣安德鲁斯大学在使用先进的核磁共振方法方面的专业知识也将有助于这项研究。已被验证为用于其选择性解聚成芳族单体的途径的木质素的一种重要转化涉及最常见的b-O-4键中的苄基羟基的选择性氧化。我们2和其他人的研究表明，这种氧化可以通过化学方法实现，但这种氧化也可以通过酶进行。为了研究这一点，学生将在韦斯特伍德实验室（圣安德鲁斯）准备合适的木质素模型化合物3，并使用这些模型来评估木质素加工酶（包括漆酶，锰过氧化物酶和将在Horsfall实验室产生的木质素过氧化物酶）进行这种氧化的能力。一旦这些方法在木质素模型化合物上进行了优化，学生将把这些方法应用于木质素本身，包括Westwood实验室中新产生的高水溶性富含b-O-4的木质素。

Fossil fuels are the major source of energy and carbon-based chemicals the world over but their use is unsustainable. A 'greener' alternative source for both the generation of fuel and raw materials is lignocellulosic biomass. The disruption of this biomass to access cellulose and hemi-cellulose for biofuels results in lignin waste of little value that constitutes 15-30% of the initial plant biomass but lignin, the 'woody' part of plants, is also a renewable substrate and a potential source of aromatic monomers. In the natural environment, microorganisms using enzymes such as laccases and peroxidases break down the lignin in biomass1. This project will study the enzymatic process of lignin degradation by such enzymes using model and waste lignins, aiming to enhance and industrialise the process. Analysis of the lignin structure remains essential if progress is to be made in deriving value from this abundant and sustainable carbon feedstock. For example, at present molecular weight determination, which is typically done by gel permeation chromatography using polystyrene standards, is proving inadequate. There is a need to improve analysis, especially when performed alongside degradation experiments as planned here. The PhD student selected will use techniques such as SEM, FT-IR and FT-ICR MS to build on our detailed analysis of readily available lignin waste products, Organosolv and Kraft lignins. Expertise from St Andrews in the use of advanced NMR methods will also contribute to this study. One important transformation of lignin that has been validated as a route for its selective depolymerisation to aromatic monomers involves selective oxidation of the benzylic hydroxyl group in the most common b-O-4 linkage. Studies by us2 and others have shown that this oxidation can be achieved using chemical approaches but this oxidation can also be carried out enzymatically. In order to study this, the student will prepare suitable lignin model compounds3 in the Westwood Lab (St Andrews) and use these models to assess the ability of lignin processing enzymes (including laccases, manganese peroxidases and lignin peroxidases that will be produced in the Horsfall lab) to carry out this oxidation. Once the methods have been optimised on lignin model compounds the student will apply these approaches to lignin itself including a newly generated highly water soluble b-O-4 rich lignin available in the Westwood lab.