MICROBIAL DEGRADATION OF DYES

DECOLORIZATION RATE OF DYES BY SEVERAL STRAINS

Abstract

Microbial degradation by several strains isolated from activated sludge was studied for azo, triphenylmethane, anthraquinone and methine dyes. The activity of the strains to degrade the dyes was evaluated from the decolorization rate of the dyes. The dyes were decolorized selectively: monoazo dyes (p-aminoazobenzene, C. I. Acid Orange 7, C. I. Acid Orange 20 and C. I. Acid Red 88), most readily; diazo dyes (C. I. Direct Red 28 and C. I. Direct Yellow 4), triphenylmethane dyes (C. I. Basic Red 9, C. I. Basic Violet 1 and C. I. Basic Violet 3), anthraquinone dye (C. I. Disperse Violet 1) and methine dye (C. I. Basic Orange 21), least readily.
The effects of the dyes on the growth of the strains were studied. From the results, it was observed that p-aminoazobenzene which was most readily decolorized by Pseudomonas sp. and C. I. Acid Orange 20 which was most readily decolorized by strain-3, had unfavorable effects on the growth of the strains, and that C. I. Direct Red 28 which was least readily decolorized by Pseudomonas sp., strain-4, strain-2 and C. I. Acid Orange 20 which was least readily decolorized by strain-l, had no effects on the growth of the strains. The permeability of the monoazo dyes through the cell membrane of Gram-negative strains was discussed.