The major objective of the research group Yeast Genetics is develop yeast as a model organism for the analysis of osmo-tolerance, and as an expression platform for heterologous gene expression. The latter is being exploited for functional gene analysis, as well as for the production of heterologous proteins. The yeast species used include both Saccharomyces cerevisiae and non-Saccharomyces yeasts such as Arxula adeninivorans. Yeasts and filamentous fungi also constitute a source of genes which could be used for metabolic redesign of plants, in order to engineer improved quality of end products, or to develop recombinant microbes for use as biosensors of environmental pollution.

The research on this topic based on our special expertise in development and application of various host vector systems based on non-conventional yeasts like Arxula adeninivorans, Hansenula polymorpha, Debaryomyces hansenii and D. polymorphus, the analysis of pathways which are unknown but of biotechnological interest and the characterization of key pathways, which play the decisive role for occurrence of exceptional properties in yeasts and filamentous fungi. The yeast A. adeninivorans for instance exhibit an extremely high level of osmo-resistance, and is particularly suitable as model organisms for a detailed analysis of this phenomenon. Our activities focus on the analysis of the key pathways which is subject to this tolerance, and the identification of compatible solutes. In addition the same yeast is able to assimilate and ferment many different substances like tannin, pyrogallol, protocatechuic acid, purine and uric acid. As the metabolism of these compounds bases on pathways that are either completely unknown or only partially characterised (e.g., tannin and purine biodegradation) they are in the focus of the group activities.

The exploitation of yeasts and fungi as a source of genes encoding proteins of biotechnological interest has been targeted predominantly at those which may have an impact on the quality of plant products. Some specific examples are the A. adeninivorans-derivedgenes encoding enzymes with broad substrate specificity such as tannase, acid phosphatase and lipase. Based on differences in substrate specificity, native and recombinant anthocyanases from various yeast species will be analysed. These enzymes are particularly suitable for decolorising anthocyanin-containing products such as grape extract.

In addition yeast strains are redesigned with new metabolic pathways in order to synthesize products of industrial interest. A first example is an A. adeninivorans strain which is able to synthesized polyhydroxyalkanoate (PHA), a biodegradable plastic. The resulting transformants accumulate high amounts of both poly-3-hydroxybutyrate (PHB) and poly-3-hydroxyvalerate (PHV), depending on the culture conditions imposed.

Another established direction in the research group surrounds the development of biosensors. The validation of a microbial estrogen sensor based on recombinant A. adeninivorans which includes the human estrogen receptor hERa is in progress. As the detection limit for 17b-estradiol as been decreased to 2ng/l, this sensor is currently the most sensitive available for endocrine-disrupting substances. Another biosensor project uses DNA and piezo-crystals for species-specific DNA-analysis. This will be developed and adapted for the taxonomic analysis of fungi (arbuscular mycorrhiza) as well as for identification of mycorrhiza residing on plant roots.
More information on these projects and other details are available in the Annual Reports of the institute.