Factors affecting water colour removal by tyrosinase

Abstract

Tyrosinase obtained from Agaricus bisporus was used to catalyze the decolourization of two reactive dyes: reactive yellow 15 (RY15) and reactive blue 114 (RB114). A 3³ factorial design was used to evaluate the effects of enzyme concentration, pH of the reaction medium and temperature on the decolourization yield. From fitted mathematical models, response surfaces were determined and the best decolourization conditions obtained were 25 °C, enzyme concentration of 200 U/L and pH 7.0. At these conditions, a maximum decolourization of 36 and 20% for RY15 and RB114, respectively, was obtained. In order to improve decolourization, aeration of the media, enzyme type (crude or lyophilized) and additives (CaCl₂ or CaCO₃) were evaluated. The lyophilized enzyme without any protective compound presented a better performance. The aeration was a very important factor confirming that oxygen was limiting the reaction. The aeration of the medium with lyophilized tyrosinase improves the dye decolourization to more than 90%.

Keywords:

• Tyrosinase
• Agaricus bisporus
• Reactive dyes
• 3³ Factorial design

Acknowledgements

Financial support for this work was in part provided by the project FCT/CAPES/(CAPES 4.1.3/CAPES/CPLP). P.F.F. Amaral and M.A.Z. Coelho thanks CNPq and FAPERJ (Brazil). This work is supported by project PEst-C/EQB/LA0020/2011 financed by FEDER through COMPETE – Programa Operacional Factores de Competitividade and by FCT – Fundação para a Ciência e a Tecnologia. A.P.M. Tavares acknowledge the financial support (Programme Ciência 2008) from FCT, Portugal. We are extremely grateful to the learned reviewer for all his help.