Hispidin (6-(3,4-dihydroxystyrl)-4-hydroxy-2-pyrone) production in submerged cultured mycelia of the basidiomycete Inonotus hispidus was doubled in shake flasks through irradiation with white light. The daily addition of 1 mM hydrogen peroxide as a chemical stressor and a repeated supplementation of the shake flask cultures with 2 mM caffeic acid, a biogenetic precursor, further increased the hispidin synthesis. These cultivation conditions were combined and applied to parallel fermentation trials on the 4 L scale using a classical stirred tank bioreactor and a wave bag bioreactor. No significant differences in biomass yield and colorant production were observed. The hispidin concentration in both bioreactors reached 5.5 g·L⁻¹, the highest ever published. Textile dyeing with hispidin was successful, but impeded by its limited light stability in comparison to industrial dyes. However, following the idea of sustainability and the flawless toxicity profile, applications in natural cosmetics, other daily implements, or even therapeutics appear promising.

Laetiporus sulphureus, a wood-decaying basidiomycete, produces yellow-orange pigments in fruiting bodies and, as was recently shown, in submerged cultivated mycelia. Out of four strains, the most potent laetiporic acid producer was identified and its yield compared in different media. The complex Moser b medium was replaced by potato dextrose broth, achieving higher yields at a lower cost. Cultivation was then scaled up from shake flask to a 7 L stirred tank bioreactor. Optimization of parameters led to increased product concentrations up to 1 g L⁻¹, the highest yield reported so far. An in situ product recovery strategy with a biphasic system was established, increasing the yield by 19% on the shake flask scale. A crude ethanolic extract of the biomass was examined for color stability and application trials. In contrast to what has been suggested in the past, the pigment showed limited long-term stability to oxygen and light, but was stable under storage in the dark at 4 °C under nitrogen. The orange extract was successfully incorporated into different matrices like foods, cosmetics and textiles. Laetiporic acid can potentially replace petrochemical based synthetic dyes, and can thus support the development of a circular bioeconomy.