Biotechnological production of fungal colorants

Since a global transformation towards circular bioeconomy relies on sustainable processes and environmentally friendly products, alternatives to currently used colorants and dyes are explored in this thesis. The proposed solutions are biotechnologically produced pigments from fungi. Two different species and their potential to produce colorants were investigated: the sulphur shelf (Laetiporus sulphureus) and shaggy bracket (Inonotus hispidus). Both species are known to synthesize colorful molecules in their fruiting bodies and in the mycelium grown in liquid culture. L. sulphureus synthesizes several orange laetiporic acids and I. hispidus produces the yellow hispidin, which is a known antioxidant with several other bioactivities. In this thesis, the cultivation of both species was scaled up from shake flask to a 4 and 7 L bioreactor and nutrition medium was optimized. By comparing four different L. sulphureus strains, the most potent pigment producer was identified and achieved yields of around 1 g/L laetiporic acid. Different physical and chemical influencing factors for improved hispidin yield were tested for the cultivation of I. hispidus. Irradiation and oxidative stress stimulated pigment synthesis, as well as supplemented precursors. The effects were combined in a comparison of two different types of bioreactors and a yield of 5.5 g/L hispidin was achieved. Different product recovery strategies were investigated, from conventional extraction to a biphasic system. The prior poor stability of laetiporic acid extracts was improved by addition of nitrogen and storage at low temperatures. The potential for application in textiles, cosmetics and food was demonstrated. In conclusion, the biotechnological production of fungal colorants was demonstrated using two examples in this thesis. Upscaling from laboratory to pilot scale was reported and optimization of chemical and physical parameters resulted in g/L-scale product titers, which render bioprocesses competitive to conventional production processes for natural colorants.