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

Stillage is an acidic residue from ethanol production that has a high carbon load. Here, Ganoderma 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 Ganoderma mycelium using rum stillage. The production of edible biomass containing bioactive products demonstrates the potential of using Ganoderma strains to valorize this residue.