P7: Comparison of the indigo carmine discoloration with two immobilization systems using chitosan as support and non purified enzymes

The textile industry is a large water consumer and produces large volumes of contaminated water, mainly containing dyes. An overview of recent studies on the discoloration of textile dyes include the use of physical chemical methods or biological, like using algae, yeast, filamentous fungi and bacteria. Enzymes have been studied to degrade the dyes too. In this work we evaluate the indigo discoloration using the Trametes versicolor extracellular enzymes immobilized in two systems: A) using chitosan and glutaldehyde and B) into alginate-chitosan spheres. Trametes versicolor culture residual medium was ultra-filtered to concentrate the enzymes, then it was used to the immobilization. It was evaluated the laccase and peroxidase activity, % of immobilized protein, rate of indigo discoloration and fitotoxicity of the products.

Using system A immobilized protein was 1.65 mg/g, specific peroxidase activity was 600 U/mg protein and specific laccase activity was 7.93 KU/mg protein; for system B the parameters were 1.47 mg/g, 300 U/g protein and 6.54 KU/mg protein respectively. Using the system A, 100 ppm of indigo carmine was discolored completely in 6.5 h, using the system B the discoloration took 34 h. For system B indigo discoloration was observed at pH 2-5; for system A discoloration was at pH 2-7. The discoloration products obtained with system A were non fitotoxic for lettuce seeds, whereas the indigo product using system B was highly fitotoxic.

Extracellular enzymes of Trametes versicolor could be immobilized without purification with a good quantity of peroxidase and laccase, enough to discolored an indigo solution