ABSTRACT
Detoxification of synthetic dyes is one of the main challenges in clearing textile industry wastes. Biodegradation of azo-dyes using Phanerochaete chrysosporium is one the most environmentally friendly methods available. The main enzymes responsible for mycodecolorization process are lignin and manganese peroxidases. Here, optimization of expression conditions has been carried out with manipulating culture condition and nutrient sources. Therefore, the effects of buffer and temperature as well as nitrogen source on lignin peroxidase and manganese peroxidase production were investigated at two levels and four levels, respectively. For this purpose, P. chrysosporium RP78 based on Taguchi design of experiment has been applied. Maximum lignin and manganese peroxidase activities of 182 +/- 2.5 U/L and 850 +/- 41 U/L were obtained under predicted optimum conditions, respectively. Thereby, about 100% decolorization was achieved after 24 h for two most widely used groups of azo dyes in textile industry consisting reactive and acidic. The physical adsorption of the azo dyes by mycelia was not significant which indicated that the enzymatic degradation of the dyes was occurred. Time profile of these enzymes showed that manganese peroxidase was peaked on 9 th day while lignin peroxidase peaked on 13 th. day and remained stable in the culture. The extracellular expression profiles of both were studied by 2 dimensional gel electrophoresis to partially characterize the enzymes
Subject(s)
Azo Compounds/metabolism , BiotransformationABSTRACT
Application of a fluidized bed bioreactor working for treatment of colored wastewaters has been studied using Phanerochaete chrysosporium fungus immobilized in calcium alginate biogel beads. The working volume of the bioreactor was 1 L; experiments were performed at room temperature and pH of culture medium was initially adjusted to 4. Manganese Peroxidase activity, glucose and ammonium concentrations have been assayed daily along the 7 operating days. Azo dye Reactive Orange 16 was added to the bioreactor after 7 days of incubation and decolorization was assayed by spectrophotometer for 1 h intervals. Maximum Manganese peroxidase activity of 96 +/- 8 U/L was obtained on day 7, and 70 +/- 3% decolorization was achieved after 6 h of dye addition. The results were compared to free cell cultures from previous studies and the role of agitation and immobilization of cells in increasing of the efficiency of decolorization was discussed. The mechanism and morphology of the immobilization of cells in ca-alginate beads were studied and the relationship between glucose and ammonium consumption and ligninolytic activity of fungi were discussed