Decolorization of practical textile industry effluents by white rot fungus Coriolus versicolor IBL-04

Abstract

Textile industry discharges a vast amount of unused synthetic dyes in effluents. The discharge of these effluents into rivers and lakes leads to a reduction in sunlight penetration in natural water bodies, which, in turn, decreases both photosynthetic activity and dissolved oxygen concentration rendering it toxic to living beings. This paper describes the decolorization potential of a local white rot fungus, Coriolus versicolor IBL-04 for practical industrial effluents collected from five different textile industries of Faisalabad, Pakistan. Screening of C. versicolor IBL-04 on five effluents showed best decolorization results (36.3%) for Arzoo Textile Industry (ART) effluent in 6 days followed by Crescent Textile Industry (CRT), Itmad Textile Industry (ITT), Megna Textile Industry (MGT) and Ayesha Textile Industry (AST) effluents. Optimization of different process parameters for ART effluent decolorization by C. versicolor IBL-04 showed that manganese peroxidase (MnP) (486 U/mL) was the lignolytic enzyme present in the culture filtrates with undetectable lignin peroxidase (LiP) and laccase. The MnP synthesis and effluent decolorization could be enhanced to 725 U/mL and 84.4%, respectively, with a significant time reduction to 3 days by optimizing pH and temperature and using 1% starch as a supplementary carbon source.

Introduction

The textile industry wastewater is rated as the most polluting among all industrial sectors in terms of both volume and composition of the effluents [1], [2]. The color in these wastewaters is due to synthetic dyes left unused due to industrial inefficiencies. Presently over 10,000 different dyes and pigments are used in dyeing and printing industries all over the world. The total world colorant production is estimated to be 800,000 tons per year and at least 10–15% of the used dyestuff enters the environment through wastes [3], [4], [5]. Many of them are believed to be toxic and carcinogenic [6].

The efficient and economical removal of these dyes from textile industry effluents is an environmental challenge [7] because of the difficulty of their removal from effluents. Literature suggests that there is a great potential for developing microbiological decolorization systems with total color removal, in some cases within few hours [8], [9]. The class of microorganisms most efficient in breaking down synthetic dyes is the white rot basidiomycetes [2]. The dye degradation property of white rot fungi (WRF) is based on their capacity to produce one or more extracellular lignin-modifying enzymes (LME), which, thanks to their lack of substrate specificity, have potential for degrading a wide range of xenobiotics [10], [11] including azo-, triphenylmethane, anthraquinone, phthalocyanine and heterocyclic dyes [12], [13], [14]. There are a considerable number of recent reports on decolorization and degradation of individual synthetic dyes by white rot fungi [6], [14], [15]. Chander and Arora [16] evaluated white rot fungi Dichomitus squalens, Daedalea flavida, Irpex flavus and Polyporus sanguineus for their potential to decolorize eight dyes, employed in different industries. D. squalens and I. flavus were found to be competitive dye decolorizers in comparison to much studied white rot fungus P. chrysosporium. Schizophyllum commune was used for the biodegradation of reactive textile dye Cibacron Red FN-2BL [17]. The fungus caused 98% dye removal catalyzed by lignin peroxidase (LiP) and manganese peroxidase (MnP) at pH 4.5 and 30 °C temperature with the addition of 1.5% (w/v) glucose as carbon source. The white rot fungi S. commune IBL-06 was found to completely (100%) decolorize direct dye Solar golden yellow R under optimum conditions secreting MnP as the major enzyme with minor laccase and LiP activities [18]. However a few studies have been reported on decolorization of complex industrial effluents [19], [20], [21], [22].

In continuation of our work on decolorization of synthetic dye solutions [15], [17], [18], this study was focused on decolorization of practical textile industry effluents by Coriolus versicolor IBL-04, optimizing the process and studying the enzymes involved in effluent degradation.