Production of laccase and use of culture filtrate for the decolorization and detoxification of textile dyes

ABSTRACTPhD. ThesisPRODUCTION OF LACCASE AND USE OF CULTURE FILTRATE FOR THE DECOLORIZATION AND DETOXIFICATION OF TEXTILE DYESByNesrin ÖZMENA thesis sumitted toDepartment of BiologyInstitute of Natural SciencesMalatya, Turkey93+xii pages2008Supervisor: Prof. Özfer YEŞİLADA (PhD)Turkey has a significant role in the world in terms of textile production. Some of the dye stuff used in the textile industry are persistent matter. Therefore, the wastewater produced from this industry has some pollution problems in the aquatic environment. In the recent years, alternative biotechnological methods are becoming more preferable to the classical applications and environmentally friendly methods are being developed for the removal of pollutants. This study aims, in addition to the production of laccase enzyme in different culture media and processes assess the usability of produced laccase depending on the used substrates.This study consists of three main sections. Initially, Astrazon blue and Astrazon black dyes were removed from aqueous environment by biosorption using lignocellulose as adsorbent in 75 to 95 %, then, these substrate were utilized for the production of laccase. Secondly, enzyme production studies were carried out. For this aim, wheat bran and copper were added to the fermentation media, and depending on this, the activities of enzyme on both bran and copper added experimental groups were investigated. Also, the cell of Trametes versicolor and Funalia trogii were adsorbed into alginate gels and it was determined that when free- and immobilized fungi mixture is used, laccase activities significantly increased. In the third section of the study, Reactive blue 19, Reactive black 5 and Reactive blue 198 dyes were exposed to both crude culture filtrate and pure (commercial) laccase enzyme and their color changes ratio were observed for 24 h period by spectrophotometrically. According to the results, while the color of Reactive blue 19 was decreased 41% with crude culter filtrate (CCF) and 70% while the with pure laccase (PL) the color of reactive black 5 was decreased 30% by CCF and 35% by PL. The color of reactive blue 198 was reduced to 56% by CCF and 71% by PL. It was found that Reactive blue 198 had the highest color change ratio. The toxic effects of decolorized dye solutions were determined by Microtox test which utilizes the inhibition characteristics of a biolumminescent bacteria, namely Vibrio fischeri. Accordingly, the toxicity of Reactive blue 19, showed very little increase after CCF application, while showing decrease with PL application. The toxicity of Reactive black 5, which was highly toxic initially, increased toxicity with both applications. There was no toxic effect for Reactive blue 198 before and after applications.KEYWORDS: dye, decolorization, white rot fungus, solid substrat fermentation, culture filtrate, laccase, microtox