Development of immobilized microbial consortia for decolorization of synthetic industrial dyes
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Date
2018-08
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
Industrial application of different types of synthetic toxic dyes in huge amount is of major concern with regard to environment and human health. Due to their carcinogenic and mutagenic properties these dyes are damaging the ecosystem and their natural flora and fauna. Therefore, the present investigation was carried out for the efficient bioremediation of seven toxic synthetic industrial dyes (direct brown, diazo black, congo red, direct black, turquoise blue, malachite green and brilliant green), which are widely used in different industries, using fourteen microbial (bacteria, fungi, yeast, microalgae and cyanobacteria) cultures. All the microbial cultures were initially screened for their in vitro dye decolorization efficiencies. Then, the selected isolates were further evaluated spectrophotometrically for the quantification of dye decolorization for all the dyes. Four fungal cultures, (PMF2, WFPN1, WDP2 and PPS1) showed maximum decolorization for most of the azo dyes, where as the microalgae (PASM, PHSM and PRSM) and the cyanobacteria (Synechococcus sp.) showed maximum decolorization for the dyes malachite green and brilliant green only in 4-7d. The microbial cocultures (consortia) were developed using the potential microbial monocultures to increase the extent of dye removal for the four selected dyes (congo red, direct black, malachite green and brilliant green). The decolorizing efficiencies shown by the selected fungal consortia for the azo dyes (congo red, direct black) and triaryl methane dyes (malachite green, brilliant green) were significantly higher than that for their monocultures. The consortia showed complete decolorization of the liquid cultures in lesser time (3-4d and upto 2d, respectively). The effect of certain factors such as concentration of dye and pH of the medium were also found to have a great impact on microbial dye decolorization. The developed microbial consortia (PHSM + Synechococcus) was able to grow and decolorize the synthetic dye (malachite green) upto a conc. of 1000 mgL-1 and could also tolerate high alkaline pH range decolorizing the dye upto pH 11. Reduction in the values of BOD, COD, electrical conductivity and pH of the treated samples as compared to their uninoculated control counterparts was also recorded. The immobilization of the co-cultures of microalgae and cyanobacteria was done on corn cob. The immobilized co-cultures showed rapid decolorization of the dye malachite green with better dye decolorizing efficacy. The extent of dye decolorization during microbial decolorization process was monitored by UV-visible spectroscopy, FTIR and SEM analysis.
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