Journal of Bioremediation & Biodegradation

Abstrait

Degradation of the Azo Dye Reactive Red 195 by Paenibacillus spp. R2

Mohd Zaini Nawahwi, Zaharah Ibrahim and Adibah Yahya

Azo dyes are a widespread class of poorly biodegradable industrial pollutants. In anaerobic environments, azo bonds are reductively cleaved yielding carcinogenic aromatic amines, many of which are assumed to resist further metabolism by anaerobes bacteria. The latter compounds generally require aerobic conditions for their degradation. A reactive group of azo dye called SFRed (C.I: Reactive Red 195) was found to be degraded using Gram negative, coccobacillus, facultative anaerobe bacteria, Paenibacillus sp. R2 to α-ketoglutaric acid with transient accumulation of 4-aminobenzenesulphonic acid (sulphanilic acid), 4-amino, 3-hydronapthalenesulphonic acid and 4-amino, 5-hydronapthalene 2,7 disulphonic acid as a degradation intermediate in anaerobic facultative batch culture. Colour and total organic carbon (TOC) was successfully removed more than 95% and up to 50% respectively. There is no significant correlation between pH and oxygen depletion since there is slightly change in pH was observed (pH from 7.21 to 7.25) though the anaerobiosis was found developed throughout the experiment (redox potential from 0.7 to 1.6 mV). The anaerobic metabolism of glucose as co-metabolite also shown to provide the electrons required for the
initial reductive cleavage of the azo group. This finding suggest that it is possible to mineralize the azo dye in the environment; thereby, avoiding accumulation of toxic intermediates in the water.