Prospecting for novel platform organisms: Taxonomic diversity of the fungal genus Aureobasidium exploited for biotechnology

The genus Aureobasidium represents a group of highly versatile yeast-like fungi. They show great adaptability to different environments and can be found in diverse ecological niches, from cold marine habitats and temperate regions, across humid and tropical areas, to warm and dry habitats. Due to its attributes the polyextremotolerant fungus has great biotechnological potential. It not only features a large substrate and product spectrum but also tolerates cold temperatures and extreme pH values as well as high salt and sugar concentrations, thus representing an extremely robust platform organism.

To identify strains for potential biotechnological applications, we performed an extensive screening of 146 strains from the genus Aureobasidium. These involved 89 strains from two strain collections and 56 new wild-type strains isolated locally from diverse natural and anthropogenic environments. The tolerances of the strains towards different pH values, high salt concentrations, and different temperatures, were investigated to discover strains thriving under extreme conditions. This potentially paves the way for developing auto-sterile processes, thus eliminating the need for costly sterilization of fermenters and equipment.

In addition, we tested different low-cost and sustainable carbon sources important in the context of a circular bio-economy. The use of such carbon sources holds the potential to establish more sustainable and economically realizable processes. Most strains could grow on a variety of lignocellulose compounds, the most abundant raw material on earth. Additionally, several strains showed growth on acetate as a carbon source, which can potentially be produced from CO₂. A waste stream from industrial ethanol production was also identified as a potential carbon source.

Overall, we showcased the suitability of Aureobasidium as a potential microbial chassis organism for industrial biotechnology and identified strains for more detailed investigations, intending to establish economically competitive and sustainable biotechnological processes.