Conversion of Soluble Compounds in Distillery Wastewater into Fungal Biomass and Metabolites Using Australian Ganoderma Isolates

Stillage is an acidic residue from ethanol production that has a high carbon load. Here, <i>Ganoderma</i> isolates were assessed for the treatment of rum stillage while producing biomass and associated metabolites. Isolates grew in 25% raw stillage, removing up to 73% of soluble organic carbon, 77% soluble nitrogen, and 74% phenolic compounds. Isolate G2 demonstrated faster removal of organic carbon and nitrogen. Biomass and metabolite production were benchmarked against a nutrient medium. In stillage, maximum values of the following were obtained: 8.2 g·L^-1 biomass; 52.8% crude protein; 22.1 mg·g^-1 extractable protein; antioxidants of 17.2 mg TE·g^-1 (2,2'-azino-di-(3-ethylbenzothiazoline-6-sulfonic acid), ABTS) and 16.6 µmol Fe²⁺·g^-1 (ferric reducing antioxidant power, FRAP); 2.9 mg GAE·g^-1 phenolic compounds (gallic acid equivalents); 1.2% lipids; and 11% β-glucans. In the nutrient medium, the following were obtained: 6.9 g·L^-1 biomass; 56.4% crude protein; 38.7 mg·g^-1 extractable protein; antioxidants of 24.9 mg TE·g^-1 (ABTS) and 25.9 µmol Fe²⁺·g^-1 (FRAP); 6.0 mg GAE·g^-1 phenolic compounds; 0.7% lipids; and 13% β-glucans. To our knowledge, this is the first report detailing the biomass metabolite content of <i>Ganoderma</i> mycelium using rum stillage. The production of edible biomass containing bioactive products demonstrates the potential of using <i>Ganoderma</i> strains to valorize this residue.