Study On The Isolation, Screening And Identification Of Cristal Violet Decoloring Strain And Its Degradation Capability

Synthetic dyestuffs are extensively used in textile, paper printing industries and dyehouses. During manufacturing and usage, an estimated 10% to 15% of total dyes are released into the environment. Dye-containing wastewater released from dye industry and dye printing industry has high chromaticity color, high chemical stability and biotoxicity, without adequate treatment, the release of coloured effluents into the environment is undesirable. Of all treatment methods, biological processes have attracted a great deal of attention, because such systems are regarded as more cost-effective and environmentally friendly.The triphenylmethane dye, crystal violet (CV), has been extensively used inindustry. There have been a few reports of CV biodegradation by bacteria. Eight strainswith decoloring capability for crystal violet were screened from the activated sludge fromtreating pools of one printing and dyeing factory, numbered F1～F8. The strain F7 whichhas the best efficiency of decoloration was identified as Stenotrophomnas maltophilia.Many factors influencing the decolorization efficiency of crystal violet with F7 in theculture media were studied. Under the optimal conditions of pH 7.0, temperature 35℃,salinity of 0.5%, inoculum size 5% and agitation rate at 150 r/min, for the solution withinitial concentration of 60 mg/L crystal violet, the decolorization rate could reach 95.7%by 8 hours. The strain F7 was immobilized with bagasse, and was used to decolor crystalviolet, for the solution with initial concentration of 20 mg/L crystal violet, thedecolorization rate could reach 95.7% by 1 hour. The immobilized live cells could bereused. After seven times reused, the decolorization rate could still reach 94%. Thedecolorizing enzymes of strain F7 were endocellular enzymes and could be producedunder non-inducting condition. The UV-visible, FTIR, HPLC were used to study thedegradation products of crystal violet. The UV-visible showed that the characteristicabsorbance peak in 589 nm and the absorption in UV district almost completelydisappeared, indicated that the conjugate structure of crystal violet was destroyed afterdegradation. FTIR showed that the absorption at 1586.47 cm^-1, 1176.79 cm^-1 and 893.93cm^-1, which were characteristic absorbance peaks of benzene ring structure, disappeared after degaradation, indicated that benzene ring structure of crystal violet was destroyed. HPLC indicated there may have formed four kinds of intermediate production during the degradation, the retention time of each was 4.346,5.972,6.388,10.137 min respectively, these intermediate productions could be further degraded. At last, the decolorization efficiency of printing and dyeing wastewater by a single strain and mixed strains was disscussed, results showed that the decolorization efficiency of mixed strains was better than single strain because of the complexity of dye-containing wastewater.