Submit Manuscript | http://medcraveonline.com Introduction The global climate change, increasing environmental pollution due to growing world population, and fast-growing industrialization resulted in rapid consumption of resources and increase in amount and variety of waste. All these developments are worrying and have forced industries and scientists to take measures against these adversities. Destruction of the natural environment we live in, which is not going to return, has been ongoing from the very old days, and recent attempts to reduce environmental pollution are very recent. Since 1980, movements towards conservation of natural life and environment have come into prominence and consumers in many countries have started to prefer products made with materials and methods that do not harm the environment during production, and post-use disposal phases. 1 The widespread environmental impact of the textile industry is manifested by discharge of high amounts of chemicals to the environment. 2 The various dyestuffs used in the textile industry are being discharged in large quantities during the production process. 3 This is the beginning of a process that is diffcult to compensate for environment and human health. 4,5 Biological approaches evaluated to reduce negative effects of waste water containing dyestuffs and chemicals have gained importance. Suggested chemical and physical treatment processes have some disadvantages such as high cost, formation of toxic by-products, excessive consumption of energy, formation of concentrated sludge, and non-adaptability to all waste water in different characters. 6–9 Therefore, biological approaches have been becoming more advantageous. The laccase enzyme, a member of peroxidases used for remediation of textile dyes, is the most promising enzyme since it can be operated without expensive cofactors. 10–12 Laccases are also increasingly used in many industrial scales such as delignifcation, biological remediation agents, ethanol production, biosensors, and bio fuels as well as dye removal. 13–22 Cotton, the most widely used natural fber in the world, needs high amounts of water during its growing and processing. The most commonly used dyestuff for dyeing this fber is reactive dyestuff, which is used and produced 80 000tons per year. Considering that about 70-150litres of water, 0.6-0.8kg of NaCl and 30-60g of dyestuffs are consumed for one kilogram of cotton dyeing, 23 the amount of pollution in the waste water that is released after dyeing is frightening. Salt, coloured and organic matters load of the wastewater discharged especially in the washing processes which are repeated in many baths after the dyeing is very high. The waste water is coloured because 20- 30% of the dyestuff used in dyeing is hydrolysed. 24–26 The reactive dyeing via exhaustion method is faced with increasingly aggressive environmental protection measures. In this regard, with this paper decolorization of wastewater after reactive dyeing of cotton fabrics was operated with commercial laccase enzyme. It was tried to determine the amount of colour removal after enzymatic decolorization of three different colour reactive dyes at three different concentrations used in the dyeing of cotton fabric. Methods In the dyeing process, Setazol Red / Blue / Orange PLF reactive dyes were used as three different concentrations (0.5, 2, 4%) together with salt (NaCl, 60g/l) and soda (Na 2 CO 3 , 20g/l). Dyeing processes were carried out at 80 °C for 60 minutes at pH=11 using ATAÇ Sample Dyeing Machine. The coloured wastewater after the dyeing process was treated with laccase enzyme (Setenzim Eco-L/SetaşKimya) at 50˚C for 40minutes. The L*, a*, b*, C*, and h° values were calculated by refectance measurements (under D65 illuminant and 10˚ standard observer) the Konica Minolta CM-3600D spectrophotometer by Color Mission software (v.3.4.1 by Argetek). The K/S values were calculated using the Kubelka-Munk equation. The colour strength (K/S) formula is presented in Equation 1. ( ) 2 1 2 R K S R − = (1) In the Formula 1, R is the decimal fraction of the refectance of fabric, K is the absorption coeffcient, and S is the scattering coeffcient. Tinctorial strengths were calculated by using maximum absorption values of each colour. In addition to tinctorial strength, absorbance values of the dyeing and enzymatic-treated baths were determined via UV-VIS spectrophotometer. The percentage decolorization was calculated as follows: (2) The amount of dyestuff remaining in the solution was calculated via Beer-Lambert law (3): J Textile Eng Fashion Technol. 2018;4(4):308‒311. 308 ©2018 Toprak et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and build upon your work non-commercially. Enzymatic Decolorization of Reactive Dyeing Baths Volume 4 Issue 4 - 2018 Tuba Toprak and Pervin Anis Department of Textile Engineering, Uludag University, Turkey Correspondence: Tuba Toprak, Textile Engineering Department, Uludag University, Gorukle Campus, Bursa, Turkey, Tel +905070099345, Email tubatoprak@uludag.edu.tr Received: June 06, 2018 | Published: July 11, 2018 Abstract Increasing social awareness and social cognition about environment are challenging the textile industry, which has highly coloured waste water. For this reason, in this study, enzymatic decolorizations of three different coloured reactive dyeing baths containing soda, salt and reactive dyes with laccase were studied. The maximum absorbance of the red coloured bath showed hypsochromic shift after enzymatic decolorization, i.e. shifted towards the blue region. The percentage of colour removal was the highest in the red and the lowest in the orange due to their tinctorial strengths. The highest colour removal among three colours were observed at 0.5 and 2% dyestuff concentrations, which indicated that laccase could be used successfully in decolorization of textile waste water. Keywords: enzymatic decolorization, environmentally friendly, sustainability, laccase, reactive dyeing, absorbance, tinctorial, hypsochromic Journal of Textile Engineering & Fashion Technology Research Article Open Access Initial absorbance Observed absorbance %Decolorization x100 Initial absorbance − =