Native fungal strains from Yucatan, an option for treatment of biomethanated vinasse

Vinasse is wastewater generated during ethanol production, with a high content of organic matter, and the presence of toxic and recalcitrant compounds that give it a dark brown color. Anaerobic digestion of vinasse is a low-cost method treatment that produces useful byproducts such as biogas. However, at anaerobic digestion of vinasse, a part of the organic matter, which includes melanoidins and phenolic compounds cannot be eliminated producing a wastewater named biomethanated vinasse (BV). It has been reported that fungi that produce ligninolytic enzymes can degrade recalcitrant compounds in raw vinasses but there is little information on the use of these microorganisms in the treatment of BV. In this work, seven fungi (Trametes hirsuta Bm-2 and AHB-6, Phanerochaete chrysosporium Bm-4, Cochliobolus lunatus AHB-1, and Athelia rolfsii AT5, AT13 and AT7) were evaluated for degrading BV. The pathogenic fungi C. lunatus and A. rolfsii species were not able to support the high concentration of toxic compounds present on the BV plate. On the other hand, Trametes hirsuta (Bm-2 and AHB-6) and Phanerochaete chrysosporium (Bm-4) can degrade and remove phenolic compounds present in BV in liquid medium. However, the Bm-2 strain it was the only microorganism able to produce a visible change in the color of the medium with a concentration of 25% BV, achieving 68.8% decolorization and 65.58% phenolic compound removal rate, with a maximum laccase activity (3415.9 U/ml) at 144 h. The results show the potential of T. hirsuta Bm-2 for degrading persistent toxic compounds present in biomethanated vinasses.