The use of soybean peroxidase in the decolourization of Remazol Brilliant Blue R and toxicological evaluation of its degradation products

This study evaluated the potential use of soybean peroxidase in the decolourization of reactive textile dye Remazol Brilliant Blue R (RBBR) and its synthetic effluent. The following parameters were studied: reaction time, dye concentration (10–60 mg L−1), enzyme load (4.96–140 U mL−1) and H2O2 concentration (20–1100 μmol L−1). The maximum removal of RBBR (86%) was obtained after 13 min of reaction, using H2O2 100 μmol L−1, enzyme 70.4 U mL−1 and RBBR 40 mg L−1. The toxicity of the products formed after enzymatic treatment was assessed by using Artemia salina and lettuce seeds (Lactuca sativa). Although soybean peroxidase was very efficient in colour removal, the products obtained after enzymatic decolourization presented higher toxicity. The inhibition concentration (IC50) obtained for lettuce seeds was 27.9%, and the lethal concentration (LC50) for A. salina was 59.3%. The aforementioned results emphasize the importance of toxicological evaluation after enzymatic treatment. The potential application of peroxidases for colour removal and the increase in the products’ toxicity reinforce the need of combined treatments.

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► High peroxidase activity was obtained from soybean-processing industry.
► No purification procedures have been performed to the crude extract;
► Peroxidase obtained from wasted seed hulls was able to remove the dye RBBR in 13 min.
► The products obtained after enzymatic decolourization presented higher toxicity.
► Results emphasize the importance of a toxicological study after enzymatic treatment.