Sweet spots for fungal lignocellulose degradation; elucidating the enzymatic mechanism underpinning interaction of Aspergillus niger with wheat straw

作为枯死植物生物量的高效降解者，真菌能够产生酶，分解组成植物细胞壁的多糖和木质素(连同木质纤维素)的复合体，形成更多的单糖。这种能力在生物技术中被利用，从小麦秸秆等可再生资源中释放糖，否则这些资源将成为农业废物。这些糖随后被用来生产生物燃料和高价值的化学品。在过去的十年里，我们对真菌遇到木质纤维素时的行为以及在这样做时产生哪些酶的了解大幅增加，特别是对于工业上重要的真菌，如黑曲霉。然而，我们对真菌酶的活性如何影响木质纤维素的了解非常有限。这项跨学科的项目旨在利用该领域的最新技术，研究黑曲霉及其酶在复杂的木质纤维素底物上降解作用的生化机制。当黑曲霉生长在木质纤维素上时，编码多糖降解酶的基因被连续打开。这表明真菌会顺序地分泌降解酶，这些酶会分解木质纤维素，瞬间暴露出单个多糖。通过这些多糖的酶降解，可溶性糖被释放出来，这些糖可以作为信号分子启动基因的表达，导致基因的顺序表达。本项目研究了木质纤维素模型麦草表面多糖的分阶段分解，以及使能酶机械的降解能力。这里将使用传统上应用于材料表面表征的最先进的工具来展示多糖是如何被真菌降解酶获取和暴露的。为了表征真菌酶，我们最近开发的一种方法将被扩展，以允许同时对许多不同的酶活性进行信息和快速筛选。该方法将用于研究黑曲霉在麦草上产生的降解酶的活性。这项研究将加深我们对真菌酶机械如何与木质纤维素相互作用和分解的理解，这是开发真菌作为酶细胞工厂的先决条件。通过研究黑曲霉木质纤维素解结构的调节和酶方面以及广泛适用的工具集而获得的理解，可用于理解其他未表现出特征的真菌种类。这项研究将由曼彻斯特大学曼彻斯特生物技术研究所萨宾·弗利奇教授的化学生物学研究组的微生物学家和酶学家乔兰达·范·蒙斯特博士进行。表面分析实验将在利兹大学植物科学中心植物细胞生物学教授Paul Knox的实验室和加拿大多伦多大学化学工程与应用化学系副教授Emma Master的实验室进行。

As efficient degraders of dead plant biomass, fungi are able to produce enzymes that can break down the complex of polysaccharides and lignin (together lignocellulose) comprising the plant cell wall, forming more simple sugars. This ability is exploited in biotechnology to release sugars from renewable resources such as wheat straw, which would otherwise be agricultural waste. These sugars are subsequently used to produce biofuels and high-value chemicals.In the last decade, our understanding of how fungi behave when encountering lignocellulose, and which enzymes they produce upon doing so has increased dramatically, especially for industrially important fungi such as Aspergillus niger. However, we have very limited understanding of how the activity of the fungal enzymes affects lignocellulose. This interdisciplinary project aims to study the biochemical mechanism underpinning the degradative effect of A. niger and its enzymes on a complex lignocellulose substrate, using state-of-the-art techniques novel to this field.When A. niger grows on lignocellulose, genes encoding polysaccharide-degradative enzymes are switched on consecutively. This suggests that the fungus sequentially secretes degradative enzymes, which deconstruct the lignocellulose to transiently expose individual polysaccharides. Via enzymatic degradation of these polysaccharides, soluble sugars are released that can act as signalling molecules to switch on expression of genes, resulting in sequential gene expression. This project investigates both the time-staged deconstruction of polysaccharides on the surface of the model lignocellulose wheat straw, as well as the degradative capacity of the enabling enzymatic machinery. State-of-the-art tools conventionally applied for the characterisation of material surfaces will be used here to show how polysaccharides are accessed by and exposed to fungal degradative enzymes. To characterise the fungal enzymes, a method that has recently been developed by us will be expanded to allow informative and fast screening of many different enzyme activities simultaneously. This method will be applied to characterise the activities of degradative enzymes produced by A. niger on wheat straw. This research will enhance our understanding of how the fungal enzymatic machinery interacts with and deconstructs lignocellulose, a prerequisite for exploitation of fungi as enzyme cell factories. Understanding gained by studying the regulatory and enzymatic aspects of A. niger lignocellulose deconstruction, as well as the broadly applicable tool set, can be applied to understand other uncharacterised species of fungi. Research will be executed by Dr Jolanda van Munster, a microbiologist and enzymologist, based in the Chemical Biology research group of Professor Sabine Flitsch, in the Manchester Institute of Biotechnology of the University of Manchester. The surface analysis experiments will be done in the laboratory of Paul Knox, Professor of Plant Cell Biology in the Centre for Plant Sciences at the University of Leeds, and in the laboratory of Emma Master, Associate Professor in the Chemical Engineering & Applied Chemistry Department, at the University of Toronto, Canada.