Removal of dyes by immobilization of Trametes versicolor in a solid-state micro-fermentation system

A novel bioreactor system (low cost and easily scaled-up) is presented for dye decolorization applying filamentous fungi. In this two-phase bioreactor, dyes were decolorized at 28 degrees C in a first phase by immobilized fungi in spherical cartridges prepared with a high-density plastic polyethylene mesh and filled with wheat bran as substrate for growth. In a second phase the capacity of the ligninolytic enzymes (laccase and Mn-peroxidase) present in the extracellular extracts from the solid residues was exploited for decolorization at 50 degrees C. Each sphere behaved as a small-scale bioreactor for cell-culture. This system allowed the decoupling of growth (sterile condition) and decolorization (non-sterile condition) stages. The ability to decolorize the azo dye xylidine and the triphenylmethane Malachite Green by two Argentinean strains of Trametes versicolor was evaluated. The highest decolorization rates were displayed by T. versicolor BAFC 2234. When both dyes were applied together in the bioreactor, after a first phase (100 min) 73.5% of Malachite Green and 40% of xylidine decolorization was attained, while at the end of the second phase (240 min) a 97% and 52% decolorization was observed. Laccase activity was detected in the decolorized solution, but no Mn-peroxidase activity. The easy change of the cartridges allows the continuous use of the bioreactor in the non-sterile decolorization of dye-containing effluents. (C) 2020 Asociacion Argentina de Microbiologia. Published by Elsevier Espana, S.L.U.

Automated summary

A novel bioreactor system using filamentous fungi for dye decolorization is presented, featuring a two-phase process utilizing ligninolytic enzymes for efficient decolorization. This system allows for growth and decolorization stages to be decoupled, achieving high decolorization rates for azo dyes and triphenylmethane. The ease of cartridge replacement enables continuous use of the bioreactor for non-sterile dye decolorization of effluents.