The filamentous fungus Aspergillus niger is well known for its capacity to secrete high amounts of proteins and metabolites, and is therefore used in industry for the production of enzymes and chemicals. The mycelium of this fungus is highly differentiated. After stationary growth phase, part of the mycelium is degraded in a process called autolysis. Autolysis is characterized by hyphal fragmentation, loss of biomass, ammonia release and the production of enzymes such as proteases and glycoside hydrolases. These glycoside hydrolases could function in degradation of cell wall polymers such as chitin. However, knowledge about the exact mechanism of autolysis is currently limited. During industrial fermentation processes, autolysis can cause the productive biomass to decrease, causing reduced product yield. A better understanding of autolysis can contribute to the formation of strategies to increase efficiency of fermentations. In order to increase understanding of the dynamics of the fungal mycelium, a consortium of academic and industrial partners investigates autolysis and differentiation in Aspergillus niger. One goal of this project is the identification and characterization of glycoside hydrolases that are involved in autolysis. By using microarrays to monitor transcription levels during growth, we have identified genes that are upregulated during the autolytic phase compared to exponential growth phase. Four of these genes belong to glycoside hydrolyse family 18, which consists mainly of (putative) chitinases. In order to investigate the properties of these enzymes we performed heterologous gene expression in E. coli with subsequent purification using affinity tags. The activity of purified proteins is investigated.
Full conference title:
7th International Aspergillus Meeting
- Asperfest 7 (2010)