Fungal Laccases and Fumonisin Decontamination in Co-Products of Bioethanol from Maize

Maize (<i>Zea mays</i> L.) may be infected by <i>Fusarium verticillioides</i> and <i>F. proliferatum</i>, and consequently contaminated with fumonisins (FBs), as well as the co-products of bioethanol intended for animal feed. Laccase enzymes have a wide industrial application such as mycotoxin degradation. The aims were to isolate and identify fungal laccase-producing strains, to evaluate laccase production, to determine the enzymatic stability under fermentation conditions, and to analyse the effectiveness in vitro of enzymatic extracts (EEs) containing laccases in degrading FB₁. Strains belonging to <i>Funalia trogii</i>, <i>Phellinus tuberculosus</i>, <i>Pleurotus ostreatus</i>, <i>Pycnoporus sanguineus</i> and <i>Trametes gallica</i> species showed laccase activity. Different isoforms of laccases were detected depending on the evaluated species. For the FB₁ decontamination assays, four enzymatic activities (5, 10, 15 and 20 U/mL) were tested, in the absence and presence of vanillic acid (VA) and 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) as redox mediators (1 and 10 mM). <i>Trametes gallica</i> B4-IMICO-RC EE was the most effective strain in buffer, achieving a 60% of FB₁ reduction. Laccases included in EEs remained stable at different alcoholic degrees in maize steep liquor (MSL), but no significant FB₁ reduction was observed under the conditions evaluated using MSL. This study demonstrate that although laccases could be good candidates for the development of a strategy to reduce FB₁, further studies are necessary to optimise this process in MSL.