CD Laboratory for Sustainable bioproduction with fungal systems through targeted strain development

Citric acid is produced industrially using the fungus Aspergillus niger. This CD Laboratory is researching selection strategies to identify and enrich particularly efficient strains. The aim is to optimise an important production process without genetic engineering.

The circular economy aims to produce renewable and sustainable chemicals. One of the most important biochemicals is citric acid, an important fruit acid that is used in the food and animal feed industry, as well as in cosmetics, medicines, cleaning agents and detergents. Citric acid has been efficiently produced industrially in large quantities for around 100 years by fermenting a sugar-containing nutrient solution with the fungus Aspergillus niger. Worldwide production is more than 2 million tonnes per year and demand is increasing.

Understanding the biological conversion process of sugar to citric acid helps in the development of highly efficient strains. Considerable progress has been made in this respect in recent years. We now know which genes in the fungal organism are responsible for switching citric acid production on and off. Such knowledge can be used to develop new, more efficient strains. In industrial food and feed production, however, this type of optimisation should be achieved without the use of genetically modified organisms (GMOs) wherever possible. For this reason, the focus of this CD Laboratory is on the selection of particularly efficient strains from naturally evolving colonies without making genetic changes.

The knowledge of the relevant genes will be used to develop targeted selection strategies and thus screen new production strains. Molecular analysis and selection tools that can be applied specifically to individual cells of Aspergillus niger will be used for this purpose. This targeted analysis of genomic data from naturally evolving populations allows a deep insight into the biology and biochemistry of the fungus and helps to uncover other key factors for efficient citric acid production. Particularly efficient strains are then specifically enriched.

In addition, a method for in vivo mRNA measurement is being developed to measure the spatial distribution of mRNA. distribution of mRNA relevant for citric acid production. In addition, novel control strategies with externally applied RNA will be tested to influence transcription patterns during citric acid production. The ability of the fungus to convert and store molecular oxygen will be analysed and the strain selection pipeline will be used to enrich for strains with improved oxygen storage capabilities.

The strains developed in this way will significantly improve citric acid production and, as they are obtained without genetic manipulation, they can be used directly in industry.