Fungal Physiology Projects

How fungi choose from nature's menu
STW 07063
Filamentous fungi play a crucial role in the global carbon cycle. They degrade and metabolise plant matter (mainly polysaccharides) and to this end produce diverse enzymatic mixtures. A complex regulatory network ensures the production of the most optimal mix of enzymes for the fungus finds itself in. It is expected that the organism will consume preferred (metabolically most favourable) carbon sources first. However, the issue of dietary preference has not been addressed before for filamentous fungi. For instance, Aspergillus niger is one of the best studied fungi with respect to plant polysaccharide degradation. However, all these studies have been performed with pure mono-, oligo- or polysaccharides. This project is aimed at understanding the substrate preferences from A. niger during growth in a natural environment. It is known that some monosaccharides (e.g. D-glucose) are better carbon sources for A. niger than others (e.g. L-arabinose). Does this imply that polysaccharides with large amounts of D-glucose are preferentially degraded compared to polysaccharides with large amount of L-arabinose? This topic will be addressed by micro-array analysis to compare the transcriptional response during growth on natural a pure substrates, and by studying the temporal and spatial expression in the colony. Moreover, identification of the responsible transcriptional regulators and studying the interaction between them will result in a better understanding of the regulatory network involved in carbon consumption of this fungus. The results of this project will significantly improve the understanding of the role of A. niger and other fungi in ecosystems.

Modification of the expression of transcriptional regulators of Aspergillus to improve industrial fermentations and use of agricultural by-products
STW 07938
Industry uses fungi from the genus Aspergillus for the production of metabolites and proteins. Production is often performed in large-scale fermentations using crude carbon sources, which consist of a variety of polymers such as starch, cellulose, xylan, xyloglucan, galacto(gluco)mannan, and pectin. These polymers are degraded by a large spectrum of secreted enzymes and the resulting degradation products are taken up by the fungus to serve as nutrients. In fact, these secreted enzymes are abundantly used in industry. The production of secreted proteins is known to be tightly regulated but little is known about the regulators involved. For instance, at least 10 regulators are expected to be involved in the degradation of sugar beet pulp but only 2 regulators have been reported in literature. The recent availability of the genome sequence (Pel et al, 2007) and DNA arrays of Aspergillus niger (facilitated by DSM) allow new approaches for the identification of transcriptional regulators of A. niger that are involved in pectin and galacto(gluco)mannan utilisation. These polymers are abundantly present in crude carbon sources. In this project we aim at identifying regulators and assess their role in extracting energy from crude carbon sources and the production of industrial enzymes and metabolites. In addition, the research should result in the production of high value products from agricultural by-products. Finally, we will evaluate to which extent these regulatory systems are conserved in fungi and transfer the knowledge obtained with A. niger to other industrial fungi and to phytopathogenic fungi.

Dissecting sequential substrate utilization in Aspergillus niger using transcriptomics and proteomics
Horizon 2008
Fungi use food sources in a specific order, by degrading these sequentially with enzymes.
The researchers will determine how this is organized for the fungus Aspergillus niger by analyzing which
enzymes are produced, and in which sequence they are produced.