Enzyme and Microbial Technology 49 (2011) 465–471 Contents lists available at ScienceDirect Enzyme and Microbial Technology jou rn al h om epage: www.elsevier.com/locate/emt Differential decolorization of textile dyes in mixtures and the joint effect of laccase and cellobiose dehydrogenase activities present in extracellular extracts from Funalia trogii Silvia Tilli, Ilaria Ciullini, Andrea Scozzafava, Fabrizio Briganti ∗ Laboratorio di Chimica Bioinorganica, Dipartimento di Chimica, Università di Firenze, Italy a r t i c l e i n f o Article history: Received 6 April 2011 Received in revised form 1 June 2011 Accepted 10 August 2011 Keywords: Textile dyes mixtures Funalia trogii Laccase Cellobiose dehydrogenase Decolorization Bioremediation a b s t r a c t The largest part of the bio-decolorization investigations have been performed to date on a single dye without exploring the behavior in complex mixtures as the real dyeing baths. Therefore, mixtures of dyes belonging to azo and anthraquinonic classes, chosen among the most utilized in textile wool dyeing, were employed for comparative enzymatic decolorization studies using the extracellular extracts from the white rot fungus Funalia trogii, to understand how the concomitant presence of more than one dye could influence their degradation course and yield. Fungal extracts containing laccase activity only were capable to partially decolorize dyes mixtures from the different classes analyzed. The deconvolution of the decolorization with time allowed to monitor the degradation of the single dyes in the mixtures evidencing a time dependent differential decolorization not observed for the singles alone. Some dyes in the blend were in fact decolorized only when the most easily converted dyes were largely transformed. These experiments would allow to help the dyeing factories in the selection of the most readily degraded dyes. Since F. trogii grown on different media and activators shows diverse levels of expression of the redox enzymes laccase and cellobiose dehydrogenase (CDH), the dyes mixtures recalcitrant to decolorization by laccase activity alone, were subjected to the combined action of extracts containing laccase and CDH. The use of CDH, in support to the activity of laccase, resulted in substantial decolorization increases (>84%) for all the refractory dyes mixtures. © 2011 Elsevier Inc. All rights reserved. 1. Introduction Synthetic dyes are extensively used in the textile, paper, tan- ning, pharmaceutical, cosmetics and food industries. Over 50,000 t of approximately 10,000 different dyes and pigments produced annually worldwide are discharged into the environment [1]. Color is usually the first contaminant to be recognized in wastewater. The discharge of less than 1 ppm for some dyes is aesthetically dis- pleasing, impedes light penetration, affects gas solubility damaging the quality of the receiving streams and may be toxic to microor- ganisms utilized in treatment processes, to food chain organisms and to aquatic life [2]. For these reasons several countries adopted demanding regulations for the release of colored industrial efflu- ents. ∗ Corresponding author at: Dipartimento di Chimica, Università degli Studi di Firenze, Via Della Lastruccia 3, 50019 Firenze, Italy. Tel.: +39 0554573343; fax: +39 0554573333. E-mail addresses: fabrizio.briganti@unifi.it, fbriganti@unifi.it (F. Briganti). Azo, anthraquinone and indigo are the major chromophores found in commercial dyes [3]. Decolorization of these dyes by phys- ical or chemical methods (adsorption and precipitation methods, chemical degradation or photodegradation) is financially and often also methodologically demanding, time-consuming and mostly not very effective [4]. The degradation of synthetic dyes in the environ- ment by microorganisms is generally very slow due to the variety of their chemical structures and properties. It is known that 90% of reactive textile dyes entering the conventional bio-treatments with activated sludge sewage treatment plants will be discharged to rivers unchanged [5]. Moreover the industrially important azo dyes, under anaerobic conditions are transformed by bacterial azo- reductases into the corresponding mutagenic and/or carcinogenic amines generating the expected health hazards [4]. As a consequence several studies have focused on the utiliza- tion of fungi since their mechanisms of dyes decolorization involve oxidative reactions which therefore do not produce toxic amines [2]. Their biodegradation capacities are generally due to highly non-specific, free-radical-mediated processes resulting from the activities of several enzymes secreted by these fungi such as laccase, manganese peroxidase (MnP) and lignin peroxidase (LiP) [6]. The 0141-0229/$ – see front matter © 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.enzmictec.2011.08.002