The project partners’ interdisciplinary research work is taking place at the wastewater treatment research facility operated by the University of Stuttgart in Büsnau. In the biorefinery concept, it undergoes dark fermentation instead, with the degradation process being halted at the stage involving production of short-chain organic acids. The microorganisms use the hydrolysate, which is rich in organic acids such as acetic, propionic and butyric acid, as a source of carbon and energy. If these organic acids are present in too high a concentration, they have toxic effects on the microorganisms. “Compared to the other bacteria we tested, Cupriavidus necator proved to be the more tolerant bacterium in contact with the organic acids,” Tamang says.