Monoazo and diazo dye decolourisation studies in a methanogenic UASB reactor

Mixed anaerobic bacterial consortia have been show to reduce azo dyes and batch decolourisation tests have also demonstrated that predominantly methanogenic cultures also perform azo bond cleavage. The anaerobic treatment of wool dyeing effluents, which contain acetic acid, could thus be improved with a better knowledge of methanogenic dye degradation. Therefore, the decolourisation of two azo textile dyes, a monoazo dye (Acid Orange 7, AO7) and a diazo dye (Direct Red 254, DR254), was investigated in a methanogenic laboratory-scale Upflow Anaerobic Sludge Blanket (UASB), fed with acetate as primary carbon source. As dye concentration was increased a decrease in total COD removal was observed, but the acetate load removal (90%) remained almost constant. A colour removal level higher than 88% was achieved for both dyes at a HRT of 24h. The identification by HPLC analysis of sulfanilic acid, a dye reduction metabolite, in the treated effluent, confirmed that the decolourisation process was due mainly to azo bond reduction. Although, HPLC chromatograms showed that 1-amino-2-naphthol, the other AO7 cleavage metabolite, was removed, aeration batch assays demonstrated that this could be due to auto-oxidation and not biological mineralization. At a HRT of 8h, a more extensive reductive biotransformation was observed for DR254 (82%) than for AO7 (56%). In order to explain this behaviour, the influence of the dye aggregation process and chemical structure of the dye molecules are discussed in the present work.     

Enzymes from spent mushroom substrate of <Emphasis Type="Italic">Pleurotus sajor</Emphasis>-<Emphasis Type="Italic">caju</Emphasis> for the decolourisation and detoxification of textile dyes

The potential of ligninolytic enzymes, including lignin peroxidase (LiP) as the main enzyme from the spent mushroom substrate of Pleurotus sajor-caju was evaluated for the decolourisation of five dyes from azo and anthraquinone dye groups. Among the azo dyes, reactive black 5 and reactive orange 16 were 84.0 and 80.9% decolourised respectively, after 4 h of incubation with 45 U of LiP as compared to 32.1% decolourisation of disperse blue 79. Among the anthraquinone dyes, disperse red 60 was decolourised to 47.2% after 4 h of incubation with 45 U of LiP as compared to 5.9% decolourisation of disperse blue 56. Increasing the LiP concentration and incubation time had a positive effect on the decolourisation of anthraquinone dyes as compared to azo dyes. A 67.9% decolourisation of synthetic textile waste-water was achieved after 4 h of incubation with 25 U of LiP. Increasing the incubation time significantly increased (P < 0.05) the decolourisation of synthetic textile waste-water. Further, there was a 52.4% reduction in the toxicity of synthetic textile waste-water treated with 55 U of LiP for 4 h. However, only 35.7% reduction in toxicity was achieved when the synthetic textile waste-water was treated with 55 U of LiP for 24 h. In this study, it was shown that the spent mushroom substrate of P. sajor-caju could be a cheap source of ligninolytic enzymes for the decolourisation of dyes in textile industry wastewaters.     

Decolorization of Acid Black 210 by <Emphasis Type="Italic">Vibrio harveyi</Emphasis> TEMS1, a newly isolated bioluminescent bacterium from Izmir Bay,Turkey

The present study deals with the decolorization of Acid Black 210 by a bioluminescent bacterium, Vibrio harveyi TEMS1, isolated from coastal seawater of Izmir Bay, Turkey. Maximum rate of decolorization of Acid Black 210 was observed when Luria Bertani medium was used. Decolorization of Acid Black 210 was 38.9% and 93.9% at 24 h under shaking and static conditions, respectively. The optimum dye-decolorizing activity of the culture was obtained at 100 ppm initial dye concentration and incubation temperature of 20°C. Vibrio harveyi TEMS1 was also tested for its ability to decolorize four azo dyes (Acid Black 24, Acid Blue 7, Acid Green 20, Acid Yellow 36) in addition to Acid Black 210.     

Effect of redox mediator, AQDS, on the decolourisation of a reactive azo dye containing triazine group in a thermophilic anaerobic EGSB reactor

The feasibility of thermophilic (55 °C) anaerobic treatment applied to colour removal of a triazine contained reactive azo dye was investigated in two 0.53 l expanded granular sludge blanket (EGSB) reactors in parallel at a hydraulic retention time (HRT) of 10 h. Generally, this group of azo dyes shows the lowest decolourisation rates during mesophilic anaerobic treatment. The impact of the redox mediator addition on colour removal rates was also evaluated. Reactive Red 2 (RR2) and anthraquinone-2,6-disulfonate (AQDS) were selected as model compounds for azo dye and redox mediator, respectively. The reactors achieved excellent colour removal efficiencies with a high stability, even when high loading rates of RR2 were applied (2.7 g RR2 l⁻¹ per day). Although AQDS addition at catalytic concentrations improved the decolourisation rates, the impact of AQDS on colour removal was less apparent than expected. Results show that the AQDS-free reactor R2 achieved excellent colour removal rates with efficiencies around 91%, compared with the efficiencies around 95% for the AQDS-supplied reactor R1. Batch experiments confirmed that the decolourisation rates were co-substrate dependent, in which the volatile fatty acids (VFA) mixture was the least efficient co-substrate. The highest decolourisation rate was achieved in the presence of either hydrogen or formate, although the presence of glucose had a significant impact on the colour removal rates.     

Batch tests for assessing decolourisation of azo dyes by methanogenic and mixed cultures

Most of the published studies on azo dye colour removal involve anaerobic mixed cultures and there is some interest in the knowledge of how dye reduction occurs, if by facultative, strictly anaerobic or both bacterial trophic groups present in classic anaerobic digestors. This paper describes the behaviour of methanogenic and mixed bacteria cultures on the colour removal in batch systems, of a commercial azo dye, C.I. Acid Orange 7, used in paper and textile industries. The aim of this study is to demonstrate, by analysing dye decolourisation, that it occurs with mixed cultures as well as with strictly anaerobic (methanogenic) cultures. Tests were performed with a range of dye concentrations between 60 and 300 mg l⁻¹. The influence of dye concentration on the carbon source removal and decolourisation processes was studied. The effect of carbon source concentration on colour removal was also analysed for both cultures. The degradation rates in mixed and methanogenic cultures were compared. The consumption of carbon source was monitored by COD analysis and dye degradation by ultraviolet-visible spectrophotometry and thin layer chromatography.     

Biological sulphate reduction and redox mediator effects on azo dye decolourisation in anaerobic–aerobic sequencing batch reactors

In this work, the anaerobic period of an anaerobic–aerobic sequencing batch reactor was found to allow the reductive decolourisation of azo dyes. 1-l reactors were operated in 24-h cycles comprising anaerobic and aerobic reaction phases, fed with a simulated textile effluent including a reactive type (Remazol Brilliant Violet 5R) or an acid type (Acid Orange 7) azo dye. The aim was to assess the role of different redox phenomena in the anaerobic decolourisation process. Selective inhibition of sulphate reducing bacteria was carried out in the sulphate-containing, reactive dye fed reactor, resulting in nearly complete, though reversible and inhibition of decolourisation. The acid dye fed reactor's supplementation with sulphate, though resulting in sulphate reduction, did not improve decolourisation. Other redox mediators, namely quinones, were more effective in promoting electron transfer to the azo bond. Bio-augmentation of the acid dye fed reactor with a pure sulphate reducer strain known to decolourise azo dyes, Desulfovibrio alaskensis, was also carried out. Decolourisation was improved, but apparently as a result of the carbon source change required to support D. alaskensis growth. A chemically mediated reduction of the azo bond coupled to biological sulphate reduction, thus seemed to account for the high decolourisation yields of both dyes.     

The use of solid waste of a nylon-6 plant as a nutrient for bacterial decolourisation of dyes

Three caprolactam-degrading bacterial isolates grew in liquid synthetic medium containing solubilised solid waste of a nylon-6 production plant as the sole source of carbon and nitrogen. Typically, the caprolactam content of solid waste was decreased by 95% in 72 h by Alcaligenes faecalis. A. faecalis was the most potent caprolactam-degrading bacterium out of the three isolates. The biomass of the bacteria obtained by growth in the solubilised solid waste medium had the ability to decolourise some synthetic azo and triphenylmethane dyes. Decolourisation of dyes was obtained in static condition, in synthetic medium which contained only the components of the solid waste as the sole sources of carbon and nitrogen and also in nutritionally rich medium. The supplementation of yeast extract to solid waste medium did not increase the efficiency of decolourisation in case of two of the bacterial cultures. Depending on the dye, medium and bacteria used, decolourisation in the range of 35–94% was achieved in 48–96 h. The decolourisation was not due to the adsorption of the dyes by the bacterial biomass except in case of Procion Blue MR and Black B. Based on these observations, the simultaneous biological treatment of the solid waste of nylon-6 plant and the decolourisation of synthetic dyes present in wastewater or solid waste is envisaged.     

Biodegradation of C.I. Reactive Red 195 by <Emphasis Type="Italic">Enterococcus faecalis</Emphasis> strain YZ66

Synthetic dyes are extensively used in textile dyeing, paper, printing, colour photography, pharmaceutics, cosmetics and other industries. Among these, azodyes represents the largest and most versatile class of synthetic dyes. As high as 50% of the dyes are released into the environment during manufacture and usage. Traditional methods of treatment are found to be expensive and have operational problems. Biological decolourization has been investigated as a method to transform, degrade or mineralize azo dyes. In the present studies bacteria from soil from dye waste area, dye waste, sewage and dung were subjected to acclimatization with C.I. Reactive Red 195 an azo dye, in the basal nutrient media. The most promising bacterial isolate was used for further dye degradation studies. The 16s rRNA gene sequencing and biochemical characteristics revealed the isolated organism as Enterococcus faecalis strain YZ66. The strain showed 99.5% decolourization of the selected dye (Reactive Red 195–50 mg/l) within one and half hour in static anoxic condition. The optimum pH and temperature for the decolourization was 5.0 and 40°C respectively. The biodegradation was monitored by UV–Vis, FTIR, TLC and HPLC. The final products were characterized by Gas chromatography and Mass Spectrophotometry. Toxicity study demonstrated no toxicity of the biodegradation product. The results suggest that the isolated organism E. faecalis strain YZ 66 can be used as a useful tool to treat waste water containing reactive dyes.     

耐碱的偶氮染料脱色菌筛选及其特性的研究

从浙江某污水处理厂的活性污泥中筛选出若干株在高pH条件下对偶氮染料酸性大红GR有脱色能力的菌株,经脱色验证得到一株具有高效脱色活性的菌株Z1,经鉴定为巴斯德葡萄球菌(Staphylococcus pasteuri),并对此菌株的脱色特性进行了初步研究。结果表明,在厌氧条件下,Z1在pH7~12,40h对50mg/L的酸性大红GR脱色率均可达90%以上。该菌株对染料有较强的耐受力,在酸性大红GR浓度为300mg/L时,48h的脱色率仍可达93%。此外,该菌株能够对多种偶氮染料脱色,具有较好的脱色广谱性,有望应用于处理工业废水中的偶氮染料。     

Decolourisation of effluent from the textile industry by a microbial consortium

Summary A microbial consortium, PDW, was isolated capable of the rapid decolourisation of commercially important textile dyes under anaerobic conditions. Decolourisation was dependent upon the presence of a carbon and energy source in addition to the textile dyes. PDW was capable of dye decolourisation when utilising cheap and readily available carbon sources such lactose, starch and distillery waste. PDW removed 76% of colour from textile plant effluent after 3 days.     

Accelerated decolorization of structurally different azo dyes by newly isolated bacterial strains

Wastewater effluents from the textile and other dye-stuff industries contain significant amounts of synthetic dyes that require treatment to prevent groundwater contamination. In research aimed at biotechnology for treatment of azo dyes, this study examined 288 strains of azo-dye degrading bacteria to identify efficient strains and determine incubation times required for decolorization. Initial enrichment cultures were carried out using a mixture of four structurally different dyes (Acid Red 88, Reactive Black 5, Direct Red 81, and Disperse Orange 3) as the sole source of C and N to isolate the bacteria from soil, activated sludge, and natural asphalt. Six strains were selected for further study based on their prolific growth and ability to rapidly decolorize the dyes individually or in mixtures. Treatment times required by the most efficient strain, AS96 (Shewanella putrefaciens) were as short as 4 h for complete decolorization of 100 mg l⁻¹ of AR-88 and DR-81 dyes under static conditions, and 6 and 8 h, respectively, for complete decolorization of RB-5 and DO-3. To our knowledge, these bacterial strains are the most efficient azo-dye degrading bacteria that have been described and may have practical application for biological treatment of dye-polluted wastewater streams.     

In vitro studies on degradation of synthetic dye mixture by Comamonas sp. VS-MH2 and evaluation of its efficacy using simulated microcosm

Reactive azo dyes are considered as one of the most detrimental pollutants from industrial effluents and therefore their biodegradation is receiving constant scientific consideration. A bacterial isolate VS-MH2, originating from dye contaminated sites of Gujarat, India, was exploited for its ability to degrade a synthetic dye mixture (SDM) (comprising of four azo reactive dyes) under static conditions. The identification of the isolate by 16S rRNA gene sequencing revealed it to be Comamonas sp. The biodegradation of the SDM was analyzed by UV-vis spectroscopy, IR spectroscopy and GC-MS analysis. The isolate showed high metabolic activity towards SDM and degraded it completely (100 mg L(-1)) within 30 h at pH 7 and 35 °C. Simulated microcosm studies in the presence and absence of indigenous microflora confirmed the ability of Comamonas sp. VS-MH2 for dye degradation and to colonize the soil. This is the first investigation reporting the degradation of SDM by Comamonas sp. under simulated soil microcosms.     

Optimisation for enhanced decolourization and degradation of Reactive Red BS C.I. 111 by Pseudomonas aeruginosa NGKCTS

Soil samples collected from dye contaminated sites of Vatva, Gujarat, India were studied for the screening and isolation of organisms capable of decolourizing textile dyes. The most efficient isolate, which showed decolourization zone of 48 mm on 300 ppm Reactive Red BS (C.I.111) containing plate, was identified as Pseudomonas aeruginosa. Reactive Red BS (C.I.111) was used as a model dye for the study. The isolated culture exhibited 91% decolourization of 300 ppm dye within 5.5 h over a wide pH range from 5.0 to 10.5 and temperature ranging from 30 to 40°C. The culture was able to decolourize more than 91% of Reactive Red BS under static conditions in presence of either glucose, peptone or yeast extract. Addition of 300 ppm of Reactive Red BS, in each step, in ongoing dye decolourization flask, gave more than 90% decolourization within 2 h corresponding to 136 mg l⁻¹ h⁻¹ dye removal rate. The isolate had the ability to decolourize six different reactive dyes tested as well as the actual dye manufacturing industry’s effluent. The degradation of the dye was confirmed by HPTLC.     

Influence of aromatic substitution patterns on azo dye degradability by Streptomyces spp. and Phanerochaete chrysosporium.

Twenty-two azo dyes were used to study the influence of substituents on azo dye biodegradability and to explore the possibility of enhancing the biodegradabilities of azo dyes without affecting their properties as dyes by changing their chemical structures. Streptomyces spp. and Phanerochaete chrysosporium were used in the study. None of the actinomycetes (Streptomyces rochei A10, Streptomyces chromofuscus A11, Streptomyces diastaticus A12, S. diastaticus A13, and S. rochei A14) degraded the commercially available Acid Yellow 9. Decolorization of monosulfonated mono azo dye derivatives of azobenzene by the Streptomyces spp. was observed with five azo dyes having the common structural pattern of a hydroxy group in the para position relative to the azo linkage and at least one methoxy and/or one alkyl group in an ortho position relative to the hydroxy group. The fungus P. chrysosporium attacked Acid Yellow 9 to some extent and extensively decolorized several azo dyes. A different pattern was seen for three mono azo dye derivatives of naphthol. Streptomyces spp. decolorized Orange I but not Acid Orange 12 or Orange II. P. chrysosporium, though able to transform these three azo dyes, decolorized Acid Orange 12 and Orange II more effectively than Orange I. A correlation was observed between the rate of decolorization of dyes by Streptomyces spp. and the rate of oxidative decolorization of dyes by a commercial preparation of horseradish peroxidase type II, extracellular peroxidase preparations of S. chromofuscus A11, or Mn(II) peroxidase from P. chrysosporium. Ligninase of P. chrysosporium showed a dye specificity different from that of the other oxidative enzymes.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of aromatic substitution patterns on azo dye degradability by Streptomyces spp. and Phanerochaete chrysosporium.

Twenty-two azo dyes were used to study the influence of substituents on azo dye biodegradability and to explore the possibility of enhancing the biodegradabilities of azo dyes without affecting their properties as dyes by changing their chemical structures. Streptomyces spp. and Phanerochaete chrysosporium were used in the study. None of the actinomycetes (Streptomyces rochei A10, Streptomyces chromofuscus A11, Streptomyces diastaticus A12, S. diastaticus A13, and S. rochei A14) degraded the commercially available Acid Yellow 9. Decolorization of monosulfonated mono azo dye derivatives of azobenzene by the Streptomyces spp. was observed with five azo dyes having the common structural pattern of a hydroxy group in the para position relative to the azo linkage and at least one methoxy and/or one alkyl group in an ortho position relative to the hydroxy group. The fungus P. chrysosporium attacked Acid Yellow 9 to some extent and extensively decolorized several azo dyes. A different pattern was seen for three mono azo dye derivatives of naphthol. Streptomyces spp. decolorized Orange I but not Acid Orange 12 or Orange II. P. chrysosporium, though able to transform these three azo dyes, decolorized Acid Orange 12 and Orange II more effectively than Orange I. A correlation was observed between the rate of decolorization of dyes by Streptomyces spp. and the rate of oxidative decolorization of dyes by a commercial preparation of horseradish peroxidase type II, extracellular peroxidase preparations of S. chromofuscus A11, or Mn(II) peroxidase from P. chrysosporium. Ligninase of P. chrysosporium showed a dye specificity different from that of the other oxidative enzymes.(ABSTRACT TRUNCATED AT 250 WORDS)     

Reactive azo dye reduction by Shewanella strain J18 143

A bacterial isolate designated strain J18 143, originally isolated from soil contaminated with textile wastewater, was shown to reduce intensely coloured solutions of the reactive azo dye, Remazol Black B to colourless solutions. Phylogenetic placement based on 16S rRNA gene sequence homology identified the bacterium as a Shewanella species. Based on results from analyses of the end products of dye decoloration of Remazol Black B and the simpler molecule, Acid Orange 7, using capillary electrophoresis, UV-visible spectrophotometry and liquid chromatography-mass spectrometry, we suggest that colour removal by this organism was a result of microbially mediated reduction of the chromophore in the dye molecules. Anaerobic dye reduction by Shewanella strain J18 143 was 30 times more efficient than the reduction carried out by aerated cultures. Whole cells used a range of electron donors for dye reduction, including acetate, formate, lactate, and nicotinamide adenine dinucleotide (NADH), with formate being the optimal electron donor. The impact of a range of process variables was assessed (including nitrate, pH, temperature, substrate concentration, presence of an extracellular mediator) and results suggest that whole cells of Shewanella J18 143 offer several advantages over other biocatalysts with the potential to treat azo dyes.     

Decolorization and degradation of Disperse Blue 79 and Acid Orange 10, by Bacillus fusiformis KMK5 isolated from the textile dye contaminated soil

The release of azo dyes into the environment is a concern due to coloration of natural waters and due to the toxicity, mutagenicity and carcinogenicity of the dyes and their biotransformation products. The dye degrading bacterial strain KMK 5 was isolated from the textile dyes contaminated soil of Ichalkaranji, Maharashtra, India. It was identified as Bacillus fusiformis based on the biochemical and morphological characterization as well as 16S rDNA sequencing. KMK 5 could tolerate and degrade azo dyes, Disperse Blue 79 (DB79) and Acid Orange 10 (AO10) under anoxic conditions. Complete mineralization of DB79 and AO10 at the concentration of 1.5g/l was observed within 48h. This degradation potential increased the applicability of this microorganism for the dye removal.     

Decolorization of textile azo dyes by newly isolated halophilic and halotolerant bacteria

Studies were carried out on the decolorization of textile azo dyes by newly isolated halophilic and halotolerant bacteria. Among the 27 strains of halophilic and halotolerant bacteria isolated from effluents of textile industries, three showed remarkable ability in decolorizing the widely utilized azo dyes. Phenotypic characterization and phylogenetic analysis based on 16S rDNA sequence comparisons indicate that these strains belonged to the genus Halomonas. The three strains were able to decolorize azo dyes in a wide range of NaCl concentration (up to 20%w/v), temperature (25-40 degrees C), and pH (5-11) after 4 days of incubation in static culture. They could decolorize the mixture of dyes as well as pure dyes. These strains also readily grew in and decolorized the high concentrations of dye (5000 ppm) and could tolerate up to 10,000 ppm of the dye. UV-Vis analyses before and after decolorization and the colorless bacterial biomass after decolorization suggested that decolorization was due to biodegradation, rather than inactive surface adsorption. Analytical studies based on HPLC showed that the principal decolorization was reduction of the azo bond, followed by cleavage of the reduced bond.     

Accumulation of Acid Orange 7, Acid Red 18 and Reactive Black 5 by growing Schizophyllum commune

The effect of Acid Orange 7, Acid Red 18 and Reactive Black 5 on the growth and decolorization properties of Schizophyllum commune was studied with respect to the initial pH varying from 1 to 6 and initial dye concentration (10-100 mg/L). The optimum pH value was found to be 2 for both growth and color removal of these azo dyes. Increasing the concentration of azo dyes inhibited the growth of S. commune. It was observed that S. commune was capable of removing Acid Orange 7, Acid Red 18 and Reactive Black 5 with a maximum specific uptake capacity of 44.23, 127.53 and 180.17 (mg/g) respectively for an initial concentration of 100 mg/L of the dye. Higher decolorization was observed at lower concentrations for all the dyes. Finally it was found that the percentage decolorization was more in the case of Reactive Black 5 dye compared to the other two dyes used in the present investigation.     

Synthetic dyes decolourisation by white-rot fungi: Development of original microtitre plate method and screening

A microtitre plate-based method was developed for a fast screening of numerous fungal strains for their ability to decolourise textile dyes. In 3 days, this method allowed to estimate significant fungal decolourisation capability by measuring the absorbance decrease on up to ten dyes. More than 325 white-rot fungi (WRF) strains belonging to 76 fungal genera were compared with regards to their capability to decolourise five azo and two anthraquinone dyes as well as the dyes mixture. The most recalcitrant dyes belonged to the azo group. Several new species unstudied in the bioremediation field were found to be able to efficiently decolourise all the dyes tested.