Evaluation of three immobilization supports and two nutritional conditions for reactive black 5 removal with Trametes versicolor in air bubble reactor

Abstract

Polyurethane foam, Luffa cylindrica sponge and Ca-alginate (3% w/v) were evaluated as immobilization supports for removing reactive black 5 dye using the white rot fungus Trametes versicolor at 1, 4 and 8 days of colonization. According to statistical results, the L. cylindrica sponge was the best support at 4 days of colonization (90% color removal). Using a factorial design 2², two nutritional conditions were evaluated with free and immobilized biomass in air bubble reactor, determining that this microorganism requires a high ratio of C/N (50:1) associated with the addition of 2 g·L^-1 of glucose and 0.05 g·L^-1 of NH₄Cl to get the maximum decolorization (86 and 87%) and enzymatic activity (1.1 and 2.1 U·L^-1) with free and immobilized biomass, respectively. The removal kinetics were evaluated in the same reactor showing a 98% of color removal obtained at 7 days with 0.84 U·L^-1, 383 U·L^-1 of laccase and lignin peroxidase activities. The bioreactor operated in three successive batches for 12 days with immobilized biomass, was maintained throughout the fermentation; the color removal was 70% with 1.3 and 300 U·L^-1 of laccase and lignin peroxidase. Finally, the UV/VIS spectrum showed that the transformation of dye was associated with biochemical and physical mechanisms.

Key words: Reactive Black 5, Trametes versicolor, immobilization supports.