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

点击翻译按钮获取中文摘要

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.