Fungal strain development for screening and production of enzymes: development of a suite of tailored Aspergillus host strains with improved characteristics regarding proteolytic degradation, enzyme screening and fermentation characteristics

Wouter de Bonte Sylvia Segers Vivi Joosten Peter Punt
., Dutch DNA Biotech, Utrecht, Netherlands

Fungal host strains such as Aspergillus niger, Aspergillus sojae and Trichoderma reesei are used for the production of a wide variety of industrially relevant enzymes. About 80% of all industrial enzymes are derived from filamentous fungi, making these organisms also the hosts of choice for the production of new enzymes and proteins.

To develop suitable strain platforms to exploit the unique characteristics of fungi several strain improvement topics are being addressed in our research. These include development of protease deficient host strains using different classical genetic and molecular genetic approaches, followed up by systems biology approaches to further explore the details of the regulation of protease production in different filamentous host strains. From our research it has become clear that various different pathways may operate in different fungi.

Besides protease production also strain improvement aimed at improved fermentation characteristics is highly relevant for protein production. In particular aspects of fungal morphology have been addressed in our research in line with fungal fermentation process engineering. This research has resulted in improved fermentation design and performance.

In many cases prior to producing specific proteins of interest also selection of genes and gene-designs for optimal protein secretion is an important step in fungal strain development. For this purpose we have developed various fungal host strains suitable for this screening phase. An example of this is a line of host strains unable to use specific polymeric carbon sources and their use to develop selective biological screens for specific protein activities.