Decolorization and partial mineralization of a polyazo dye by Bacillus firmus immobilized within tubular polymeric gel

Abstract

The degradation of C.I. Direct red 80, a polyazo dye, was investigated using Bacillus firmus immobilized by entrapment in tubular polymeric gel. This bacterial strain was able to completely decolorize 50 mg/L of C.I. Direct red 80 under anoxic conditions within 12 h and also degrade the reaction intermediates (aromatic amines) during the subsequent 12 h under aerobic conditions. The tubular gel harboring the immobilized cells consisted of anoxic and aerobic regions integrated in a single unit which was ideal for azo dye degradation studies. Results obtained show that effective dye decolorization (97.8%), chemical oxygen demand (COD) reduction (91.7%) and total aromatic amines removal were obtained in 15 h with the immobilized bacterial cell system whereas for the free cells, a hydraulic residence time of 24 h was required for an equivalent performance in a sequential anoxic and aerobic process. Repeated-batch experiments indicate the immobilized cells could decolorize C.I. Direct red 80 and reduce medium COD in five successive batch runs with enhanced activity obtained after each consecutive run, thus suggesting its stability and potential for repeated use in wastewater treatment. UV–visible spectrophotometry and HPLC analysis were used to confirm the partial mineralization of the dye. Data from this study could be used as a reference for the development of effective industrial scale biotechnological process for the removal of dyes and their metabolites in textile wastewater.

Application of response surface methodology for optimization of decolorization and mineralization of triazo dye Direct Blue 71 by Pseudomonas aeruginosa

“…However, subsequent incubation for 24 h under aerobic conditions resulted in 78.39 % reduction in TOC thus, suggesting the substantial conversion of the azo dye to CO 2 by P. aeruginosa under these conditions. The switch to aerobic condition after 48 h of reduced oxygen concentration was to encourage the degradation of resultant decolorization metabolites (aromatic amines) which can only be mineralized under aerobic condition (Khosravi et al 2013 ; Ogugbue et al 2012a ). No changes in TOC levels were obtained in the controls and in filter-sterilized microaerophilic-treated cultures.…”

“…However, the use of bacterial cultures is preferable since they exhibit a rapid growth rate and require shorter hydraulic retention time for dye decolorization. Previous reports indicated that bacterial strains like Bacillus firmus (Ogugbue et al 2012a ), Aeromonas hydrophila (Ogugbue et al 2012b ), Klebsiella sp. strain VN-31 (Franciscon et al 2009 ), Sphingomonas sp.…”

Strategic Design of Synthetic Consortium with Embedded Wastewater Treatment Potential: Deciphering the Competence of Isolates from Diverse Microbiome

“…B. firmus is capable of producing xylanases (Min-Jen et al, 2002) at alkaline conditions. It widely used of dye removal from textile wastewater (Ogugbue et al, 2012). P. otitidis was studied for its bioplastics production and dye degradation (Wu et al, 2009;Reddy et al, 2012).…”

Biodegradation and detoxification of textile azo dyes by bacterial consortium under sequential microaerophilic/aerobic processes

“…2) ). A previous study on aerobic decolorization of azo dyes has also shown that this process is insufficient to completely degrade most of azo dyes (Ogugbue et al, 2012[ 38 ]).…”

“…Formation of aromatic amines by bacterial degradation of azo dyes under microaerophilic conditions has been reported (Franciscon et al, 2009[ 15 ]). Aerobic treatments for biodegradation of azo dyes have also been reported; however, such oxidative break-down of azo bond is not sufficient to completely mineralize them into nontoxic form (Ogugbue et al, 2012[ 38 ]). Hence, in the present study the safe biode-gradation processes for complete mineralization of azo dyes without formation of aromatic amines have been evaluated.…”