J.Chem.Soc.Pak., Vol. 33, No. 2, 2011 209 Shake Flask Decolourization of Direct Dye Solar Golden Yellow R by Pleurotus ostreatus KASHIF JILANI*, MUHAMMAD ASGHER, HAQ NAWAZ BHATTI AND ZAHID MUSHTAQ Department of Chemistry and Biochemistry, University of Agriculture, Faisalabad, 38040, Pakistan. (Received on 4 th May 2010, accepted in revised form 17 th August 2010) Summary: Different on site treatment technologies are in practice for industrial wastewaters but bioremediation using white rot fungi is the most attractive option due to complete degradation of the pollutants to non toxic end products. Three direct dyes (Solar golden yellow R, Solar brilliant red BA and Solar orange RSN) were decolourized using white rot fungus (WRF) Pleurotus ostreatus. The best decolourized dye Solar golden yellow R was selected for subsequent optimization studies for decolourization. Under optimum conditions Pleurotus ostreatus caused 90.32 % decolourization of 0.01 % Solar golden yellow R solution within two days of shake flask incubation at pH 3.5 and 30 º C temperature in Kirk’s basal nutrient medium with added 1 % starch and 0.01 % ammonium sulphate as carbon and nitrogen sources, respectively. Ligninolytic enzyme activities were correlated to dye decolourization and maximum laccase activity of 356.23 U/ml was also noted in the maximally decolourized medium. Introduction Environmental pollution has increased with increasing industrial developments [1-3]. Chemical contamination of water by a wide range of pollutants is a serious environmental problem due to their potential human toxicity. The textile industry generates substantial quantities of waste waters containing large amount of dissolved dyestuffs and other products, such as dispersing agents, dye bath carriers, salts, emulsifiers, leveling agents and heavy metals [4]. The total world colorants production is estimated to be 8, 00,000 tons per year and at least 10 % of the used dyestuffs enter the environment through textile and other mills effluents [5-7]. Dyes are synthetic chemical compounds having structures that are stable against the harsh environmental conditions, such as light, pH and temperature are difficult to be eliminated by conventional chemical and biological wastewater treatment methods [8]. The utilization of biodegradative abilities of white rot fungi (WRF) seems to be promising in this regard. Owing to their extracellular non-specific free radical-based enzymatic system, WRF can degrade to non-detectable levels or even completely eliminate a variety of xenobiotics including synthetic dyes [9- 11]. There is considerable number of studies on decolourization and degradation of dyes by WRF that has been reported [12]. Since the ligninolytic enzymes of WRF comprising mainly lignin peroxidase (LiP), manganese peroxidase (MnP) and laccase are extracellular and substrate non-specific, these are capable of degrading a range of recalcitrant compounds including complex aromatic pollutants and synthetic dyestuffs [13]. Lignin peroxidase catalyzes the oxidation of non phenolic aromatic lignin moieties and similar compounds [14-16]. Manganese peroxidases are glycosylated glycoproteins [17] with an iron protoporphyrin IX (heme) prosthetic group [18]. Laccase is a ubiquitous enzyme among basidiomycetes [19]. Compared with Phanerochaete chrysosporium, Pleurotus ostreatus produces laccases instead of LiP as the major enzyme responsible for the biodegradation of lignin and textile dyes [20, 21]. The lignin-degrading ability of WRF has been the focus of intensive research efforts for many years and has been exploited for a wide array of human benefits. This paper presents the results of a study carried out to develop a decolourization process for a direct dye Solar golden yellow R using an indigenous strain of Pleurotus ostreatus. Results and Discussion Locally isolated Pleurotus ostreatus was screened on three direct textile dyes being extensively used in local textile processing industries of Faisalabad, Pakistan. It was noted that decolourization of all dyes increased gradually with the passage of time and on 5th day P. ostreatus showed 84.65, 70.3 and 59.44 % decolourization of Solar golden yellow R, Solar brilliant red BA and Solar orange RSN, respectively (Table-1). The best decolorized dye Solar golden yellow R was selected for subsequent optimization studies. J.Chem.Soc.Pak., Vol. 33, No. 2, 2011 * To whom all correspondence should be addressed.