Microaerophilic–aerobic sequential decolourization/biodegradation of textile azo dyes by a facultative Klebsiella sp. strain VN-31

Abstract

Four different azo dyes were decolourized and biodegraded in a sequential microaerophilic-aerobic treatment by a facultative Klebsiella sp. strain VN-31, a bacterium isolated from activated sludge process of the textile industry. Dye decolourization was performed under microaerophilic conditions until no colour was observed (decolourization percentage >94%). The medium was then aerated to promote the biodegradation of the amines produced. The presence of aromatic amine in the microaerophilic stage and its absence in the aerobic stage demonstrate azo bond reduction and an oxidative biodegradation process, respectively. Total Organic Carbon (TOC) reduction for the growth medium plus dyes was $50% in the microaerophilic stage and $80% in the aerobic stage. The degradation products were also characterized by FT-IR and UV-vis techniques and their toxicity measured using Daphnia magna. The results provide evidence that the successive microaerophilic/aerobic stages, using a single Klebsiella sp. strain VN-31 in the same bioreactor, were able to form aromatic amines by the reductive break down of the azo bond and to oxidize them into non-toxic metabolites.

Destruction of azo dyes by anaerobic–aerobic sequential biological treatment: a review

“…The concentration and number of aromatic amines generated are found to be in accordance with the number of azo bonds in the chemical structure of the dye (Franciscon et al 2009). Some of the evidences of amine generation were based on quantitative direct detection of individual compounds.…”

“…Thus, the dye-containing wastewater may be toxic due to inherent toxicity and mutagenicity of dyes. The reactive dyes and hydrolysed reactive dyes have a lower toxicity potential in aquatic organisms as compared to acid, basic and disperse dyes (Franciscon et al 2009). Anaerobic decolourization by cleavage of azo bond generates aromatic amines, which are in some cases more toxic than the parent dyes.…”

Biological Treatment of Cyanide by Using Klebsiella pneumoniae Species

“…Klebsiella sp., which is a natural colonizer of humans, vertebrates, birds, reptiles and even insects, is also isolated from contaminated areas such as soil and wastewaters (14)(15)(16)(17). Accordingly, Klebsiella sp.…”

“…Accordingly, Klebsiella sp. is used as a remediation agent in research of the removal of azo dyes, phenols, hexahydro-1,3,5-trinitro-1,3,5-triazine, organochlorine insecticides, aromatic amines and many other toxic substances (16)(17)(18)(19). However, biodegradation of diff erent cyanide sources, optimization of medium containing cyanide and eff ect of diff erent ions on cyanide biodegradation using K. pneumoniae have not been studied yet.…”

“…However, biodegradation of diff erent cyanide sources, optimization of medium containing cyanide and eff ect of diff erent ions on cyanide biodegradation using K. pneumoniae have not been studied yet. Therefore, in this study, the aim is to investigate the cyanide biodegradation abilities of 17 …”