Jafari Narjes, Kasra-Kermanshahi Rouha, Soudi Mohammad Reaz
Department of Biology, Faculty of Science, Alzahra University, Tehran, Iran.
Iran J Microbiol. 2013 Dec;5(4):434-40.
Synthetic dyes are recalcitrant to degradation and toxic to different organisms. Decolorization of textile wastewaters is one of the major concerns since last decades. Physical-chemical treatments are very expensive and frequently producing large amounts of toxic wastes. Biological treatments can be more convenient. In the present study, an attempt has been made for decolorization of azo dyes using microbial process.
Screening of microorganisms capable of azo dye decolorization was performed from activated sludge. The decolorization of various dyes (Reactive Black 5, Reactive Orange 16, Reactive Red 198, Direct Blue 71, Direct Yellow 12 and Direct Black 22) was determined by measuring the absorbance of culture supernatant at their λmax. Culture supernatants were also analyzed for UV-Vis absorption between 200-800 nm. The effect of aeration, temperature, different concentrations of glucose and NaCl was studied with an aim to determine the optimal conditions required for maximum decolorization.
The yeast (strain JKS4) which had high ability to decolorize different azo dyes was isolated. Under aerobic condition, the yeast strain showed 85.7% of decolorization at 200 mg/l Reactive Black 5 (as a model azo dye), 1% (w/v) glucose concentration and 35°C after 24 h. All the examined dyes were extensively decolorized (53.35-97.9%) after 24 h. With elongated incubation period, complete decolorization was observed in presence of all dyes. From the physiological properties and phylogenetic analysis based on the 26S rDNA sequences, strain JKS4 was classified into Candida palmioleophila.
Because of high decolorizing activity against various azo dyes commonly used in the textile industries, it is proposed that the isolated yeast may have a practical application in the biotransformation of various dye effluents.
合成染料难以降解且对不同生物具有毒性。过去几十年来，纺织废水的脱色一直是主要关注点之一。物理化学处理成本高昂，且常常产生大量有毒废物。生物处理可能更为便捷。在本研究中，尝试采用微生物方法对偶氮染料进行脱色。
从活性污泥中筛选能够对偶氮染料进行脱色的微生物。通过测量培养上清液在其最大吸收波长（λmax）处的吸光度来测定各种染料（活性黑5、活性橙16、活性红198、直接蓝71、直接黄12和直接黑22）的脱色情况。还对培养上清液在200 - 800 nm之间进行紫外可见吸收分析。研究了曝气、温度、不同浓度葡萄糖和氯化钠的影响，以确定实现最大脱色所需的最佳条件。
分离出了对偶氮染料具有高脱色能力的酵母（菌株JKS4）。在有氧条件下，该酵母菌株在200 mg/l活性黑5（作为偶氮染料模型）、1%（w/v）葡萄糖浓度和35°C条件下培养24小时后，脱色率达85.7%。所有检测的染料在24小时后均被大量脱色（53.35 - 97.9%）。随着培养时间延长，在所有染料存在的情况下均观察到完全脱色。根据基于26S rDNA序列的生理特性和系统发育分析，菌株JKS4被归类为嗜油假丝酵母。
由于对纺织工业中常用的各种偶氮染料具有高脱色活性，建议分离出的酵母在各种染料废水的生物转化中可能具有实际应用价值。
