Exploring threshold operation criteria of biostimulation for azo dye decolorization using immobilized cell systems

This follow-up study provided an evaluation on threshold operation criteria of biostimulation in immobilized cell systems (ICSs) with Aeromonas hydrophila onto packing materials Porites corals. Essential nutrients in appropriate flow rate for biostimulation were inevitably required to maintain maximum attached cell population for cost-effective biodecolorization. With the method of “graphical reconstruction”, the most economically feasible strategy of medium stimulation for color removal was quantitatively revealed. Our findings pointed out no matter what operation mode of reactor was (e.g., suspended batch cultures or ICS) color removal efficiency for A. hydrophila still strongly depended upon intrinsic kinetics and chemical reactivities of azo dyes. Mass transport effects in ICS might not play most significant roles to limit dye biodecolorization of A. hydrophila (except Reactive red 198, Reactive green 19), as relative rankings of color removal rates of various dyes were almost in parallel with those in suspended batch cultures.     

Proposed pathways for the reduction of a reactive azo dye in an anaerobic fixed bed reactor

Some process has been proposed for azo dye degradation and anaerobic bioreactors are one of them, since for their reduction, the dye has to be the electron acceptor. An anaerobic fixed bed bioreactor packed with activated carbon (AC) is proposed to degradate the Reactive Red 272 azo dye. In the present paper a dye degradation mechanism in an anaerobic environment is explained. It is very important to consider the interaction dye-microorganism-AC, because the groups in the AC surface take part in the reaction besides being an excellent carrier for microorganism and an adsorbent for the dye. The aromatic compounds produced in the dye reduction are partially degraded as a function of inlet dye concentration and reactor residence time. In anaerobic environment the aromatic compounds are decomposed through hydroxylation, carboxylation and redox reactions, due to enzymatic reactions.     

Reactive red azo dye degradation in a UASB bioreactor: Mechanism and kinetics

Textile industry uses azo dyes in its processes, which are complex organic molecules that are not easy to be degraded. Reactive dyes are especially difficult to remove from wastewater because of the characteristics of the molecule: one or more azo bonds, naphthalene‐disulfonate, triazine or chloro‐triazine, and phenyl‐amine groups. The degradation of the azo dye reactive red 272 was studied under anaerobic conditions in a hybrid Upflow Anaerobic Sludge Bed reactor (UASB) with an activated carbon bed. An adapted consortium of microorganisms was used in the kinetic study (batch) and to inoculate the UASB reactor. The experimental design identified the main factors determining the dye reduction efficiency are the initial concentration of dye and dextrose (as electron donor) and the residence time in the reactor. Dye reduction rate was decreased as the concentration increases in the wastewater; as a result, a kinetic model with a change from first to second order is proposed. The kinetic study showed that the process is first abiotic (adsorption) and then biotic (biodegradation).     

Efficient decolorization and detoxification of sulphonated azo dye Ponceau 4R by using single and mixed bacterial consortia

Abstract

The decolorization of toxic azo dye Ponceau 4R by three strains of bacteria Bacillus sp. strain AK1, Lysinibacillus sp. strain AK2 and Kerstersia sp. strain VKY1 individually and in consortia was studied. At optimal conditions, up to 95%, 93% and 87% of the dye was decolorized by the strains AK1, AK2 and VKY1, respectively, in 24?h at 200?mg/L of the dye. Decolorization of the dye was optimized for different parameters such as the concentration of dye, pH, temperature and NaCl concentration. These strains were able to decolorize Ponceau 4R up to an initial concentration of 800?mg/L in the pH range of 5–10, temperature 25–55?°C and NaCl concentration up to 30?g/L. The dye decolorization efficiency of these strains was further enhanced by using different consortia of AK1, AK2 and VKY1 in various combinations. The complete decolorization of the dye by a consortium was achieved within 18?h at 200?mg/L. The cell-free extract of these strains grown on this dye exhibited a remarkable activity of azoreductase which is involved in the breakage of the azo bond. The steady-state kinetics of azoreductase, validated the ping pong Bi-Bi mechanism of enzyme action. UV–Vis spectra, HPLC, FTIR and LC-MS analysis of the dye decolorized samples showed the formation of 4-aminonaphthalene-1-sulphonic acid and 5-amino-6-hydroxynaphthalene-2, 4-disulphonic acid as the products of azo bond breakage. The phytotoxicity test of decolorized sample revealed a considerable reduction in the toxicity in comparison with the parent dye.     

Production of laccase by a newly isolated deuteromycete fungus <Emphasis Type="Italic">Pestalotiopsis</Emphasis> sp. and its decolorization of azo dye

The effect of various carbon and nitrogen sources on the production of laccase by newly isolated deuteromycete Pestalotiopsis sp. was tested under liquid-state fermentation. Twenty grams per liter of glucose and 10 g l⁻¹ ammonium tartrate were found to be the optimized concentrations of carbon and nitrogen sources, respectively. The influence of different inducers and inhibitors on the laccase production was also examined. Adding the Cu up to optimum concentration of 2.0 mM in medium (include 20 g l⁻¹ glucose and 10 g l⁻¹ ammonium tartrate), the highest laccase activity of 32.7 ± 1.7 U ml^−l was achieved. Cu had to be supplemented after 2 days of growth for its maximal effect, an addition after 6 days of growth, during which laccase activity was dominantly formed, resulted in distinctly reduced laccase activity. In addition, Direct Fast Blue B2RL can be effectively decolorized by crude laccase, the decolorization percentage of which was 88.0 ± 3.2% at pH 4.0 within 12 h. The results suggest that Pestalotiopsis sp. is a high potential producer of the industrially important enzyme laccase.     

Enhanced decolorization of sulfonated azo dye methyl orange by single and mixed bacterial strains AK1, AK2 and VKY1

Abstract

Methyl orange, a sulfonated azo dye having various industrial applications was decolorized by three bacteria Bacillus sp. strain AK1, Lysinibacillus sp. strain AK2 and Kerstersia sp. strain VKY1. The effect of various factors such as dye concentration, pH, temperature and NaCl concentration on decolorization was investigated. At 200?mg/L methyl orange concentration, the strains AK1, AK2 and VKY1 exhibited maximum decolorizing potential of 93, 95 and 96%, respectively, at temperature 35?°C and pH 7.0 within 18?h of incubation. These strains decolorized the dye over a wide range of pH (5–10), temperature (15–55?°C), and NaCl concentration (5–20?g/L). Further, these strains decolorize up to 800?mg/L concentrations of methyl orange within 24?h. The dye decolorization efficiency was further increased by using different consortia of these three strains which could decolorize the dye completely within 12?h of incubation. The cell-free extracts of the strains AK1, AK2 and VKY1 grown on methyl orange exhibited the azoreductase activity of 0.4794, 1.56 and 1.01?µM/min/mg protein, respectively. HPLC and FTIR analysis of the dye decolorized sample indicated the formation of 4-aminobenzenesulfonic acid and N,N-dimethyl-p-phenylenediamine as breakdown products of azo bond. The high decolorization potential of these bacterial strains individually and in consortia has potential application in remediation of dye effluent.     

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.     

Assessment of the biodegradability of a monosulfonated azo dye and aromatic amines

Biodecolourisation of an azo dye by anaerobic cultures using a liposomal textile levelling agent as primary substrate was assessed. Liposomes seem to facilitate the uptake of the dye (Acid Orange 7) by anaerobic biomass, leading to a fast decolourisation (colour removal of 96% was achieved in the first sample port of the reactor profiles). On the other hand, the presence of dye (60–300 mg l⁻¹) caused a decrease in the chemical oxygen demand (COD) degradation rate (4.1–2.5 g COD removed l⁻¹ d⁻¹ for 60 and 300 mg l⁻¹ of dye, respectively), suggesting inhibitory effects.Aerobic degradation of aromatic amines was investigated in aerobic respirometric assays with different types of inocula. Sulfanilic acid and aniline were mineralised by inocula with a significant microbiological diversity, even with domestic effluent. These results were confirmed by a significant reduction of COD, total organic carbon (TOC) and a high oxygen consumption (biochemical oxygen demand/theoretical oxygen demand), 92±4%. Kinetic analysis showed that a sigmoid function describes quite well the experimental data, even better than the exponential model. Orthanilic and metanilic acids and 1-amino-2-naphtol were persistent under the tested conditions.     

Decolorization of azo and triphenylmethane dyes by Pycnoporus sanguineus producing laccase as the sole phenoloxidase

Partial decolorization of two azo dyes (orange G and amaranth) and complete decolorization of two triphenylmethane dyes (bromophenol blue and malachite green) was achieved by cultures in submerged liquid culture producing laccase as the sole phenoloxidase. Enzyme production could be correlated with dye decolorization, with sorption of dye to mycelia accounting for less than 3% of dye removal.     

A novel moderately halophilic bacterium for decolorizing azo dye under high salt condition

Halomonas sp strain GTW was newly isolated from coastal sediments contaminated by chemical wastewater and was identified to be a member of the genus Halomonas by 16S rDNA sequence analysis and physical and biochemical tests. The optimal decolorization conditions were as follows: temperature 30°C, pH 6.5.0–8.5, NaCl 10–20% (w/v) and the optimal carbon source was yeast exact. The results of experiments demonstrated that the bacteria could decolorize different azo dyes under high salt concentration conditions, and the decolorization rate of five tested azo dyes could be above 90% in 24 h. The exploitation of the salt-tolerant bacteria in the bio-treatment system would be a great improvement of conventional biological treatment systems and the bio-treatment concept.     

Decolorization of diazo dye Direct Red 81 by a novel bacterial consortium

Summary Samples collected from various effluent-contaminated soils in the vicinities of dyestuff manufacturing units of Ahmedabad, India, were studied for screening and isolation of organisms capable of decolorizing textile dyes. A novel bacterial consortium was selected on the basis of rapid decolorization of Direct Red 81 (DR 81), which was used as model dye. The bacterial consortium exhibited 90% decolorization ability within 35 h. Maximum rate of decolorization was observed when starch (0.6 g l⁻¹) and casein (0.9 g l⁻¹) were supplemented in the medium. Decolorization of DR 81 was monitored by high performance thin layer chromatography, which indicated that dye decolorization was due to its degradation into unidentified intermediates. The optimum dye-decolorizing activity of the culture was observed at pH 7.0 and incubation temperature of 37 °C. Maximum dye-decolorizing efficiency was observed at 200 mg l⁻¹ concentration of DR 81. The bacterial consortium had an ability to decolorize nine other structurally different azo dyes.     

Biodegradation of textile azo dye by <Emphasis Type="Italic">Shewanella decolorationis</Emphasis> S12 under microaerophilic conditions

The complete biodegradation of azo dye, Fast Acid Red GR, was observed under microaerophilic conditions by Shewanella decolorationis S12. Although the highest decolorizing rate was measured under anaerobic condition and the highest biomass was obtained under aerobic condition, a further biodegradation of decolorizing products can only be achieved under microaerophilic conditions. Under microaerophilic conditions, S. decolorationis S12 could use a range of carbon sources for azo dye decolorization, including lactate, formate, glucose and sucrose, with lactate being the optimal carbon source. Sulfonated aromatic amines were not detected during the biotransformation of Fast Acid Red GR, while H₂S formed. The decolorizing products, aniline, 1,4-diaminobenzene and 1-amino-2-naphthol, were followed by complete biodegradation through catechol and 4-aminobenzoic acid based on the analysis results of GC-MS and HPLC.     

产漆酶疣孢漆斑菌NF-05的分离及对偶氮染料的脱色

以木质素磺酸钠为唯一碳源的培养基对带岭凉水自然保护区土壤样品进行富集培养,涂布于愈创木酚-PDA平板。经2,2′-连氮-双(3-乙基苯并噻唑-6-磺酸)（ABTS）和丁香醛联氮（SGZ）平板检测初筛,ABTS法测定摇瓶发酵液酶活力复筛,筛选到一株漆酶高产真菌NF-05。形态学观察结合rDNA-ITS序列分析,鉴定该菌为半知菌疣孢漆斑菌Myrothecium verrucaria。该菌株在液体产酶培养基中生物量积累与产酶基本同步,发酵第5天达到产酶高峰,最高酶活力为8,375.87U/L。纯化漆酶对偶氮染料脱色研究结果表明,该酶在96h对甲基橙脱色率达到90%以上,以2,2,6,6-四甲基哌啶氧化物（TE）为介体时,48h脱色率即达90%以上;该酶在24h对橙黄Ⅰ的脱色率即达90%以上;以TE为介体时,该酶在24h即使橙黄G6完全脱色。     

A study on the utility of immobilized cells of indigenous bacteria for biodegradation of reactive azo dyes

Abstract

Azo dyes are recalcitrant compounds used as a colorant in various industries. The pollution caused by their extensive usage has adversely affected the environment for years. The existing physicochemical methods for dye pollution remediation are rather inefficient and hence there is a dearth of low-cost, potential systems capable of dye degradation. The current research studies the biodegradation potential of immobilized bacterial cells against azo dyes Reactive Orange 16 (RO-16) and Reactive Blue 250 (RB-250). Two indigenous dye degrading bacteria Bacillus sp. VITAKB20 and Lysinibacillus sp. KPB6 was isolated from textile sludge sample. Free cells of Bacillus. sp. VITAKB20 degraded 92.38% of RO-16 and that of Lysinibacillus sp. KPB6 degraded 95.36% of RB-250 within 72?h under static conditions. Upon immobilization with calcium alginate, dye degradation occurred rapidly. Bacillus. sp. VITAKB20 degraded 97.5% of RO-16 and Lysinibacillus sp. KPB6 degraded 98.2% of RB-250 within 48?h under shaking conditions. Further, the nature of dye decolorization was biodegradation as evident by high-performance liquid chromatography (HPLC), and Fourier-transform infrared spectroscopy (FTIR) results. Phytotoxicity and biotoxicity assays revealed that the degraded dye products were less toxic in nature than the pure dyes. Thus, immobilization proved to be a highly likely alternative treatment for dye removal.     

Phytoremediation of textile effluents containing azo dye by using Phragmites australis in a vertical flow intermittent feeding constructed wetland

An azo dye, acid orange 7 (AO7), was selected to study the role of Phragmites australis (P. australis) peroxidases (POD) activity in its degradation in a vertical flow constructed wetland (VFCW). Crude plant extract was found to degrade AO7 and its aromatic amines, after 120 h in contact with H₂O₂, and removals of were obtained for 40 mg_AO7 l⁻¹ ().The VFCW was found to be suitable to treat an effluent containing an azo dye. For influent concentrations of 130 mg_AO7 l⁻¹ POD activity increased 2.1-, 4.3- and 12.9-fold for leaves, stems and roots, respectively. At 700 mg_AO7 l⁻¹, inhibition of POD activity occurred immediately, but it returned to the previous levels after only 2 days. An AO7 organic load of 21 up to 105 g COD m² day⁻¹, revealed non-toxicity, being expectable to achieve removals of 11 up to 67 g COD m² day⁻¹. Both [AO7] and TOC removal efficiencies were found to be similar (approximately 70%), which is indicative of AO7 mineralization. A 3 h cycle was found to be sufficient to degrade AO7 and a system buffering capacity from 5 to 25 min cycle⁻¹ was demonstrated by flooding level control.     

Dynamic transport and reaction model for azo dye removal in a UAFB reactor

An Upflow Anaerobic Fixed Bed (UAFB) reactor packed with activated carbon was used to remove the azo dye Reactive red 272. The biomass grown on the activated carbon surface was composed of an adapted consortium of microorganisms. Residence time distribution test indicated that the reactor was a plug flow behavior. A dynamic mathematical model is presented for dye flux along the reactor and within the bioparticles composed of two regions: activated carbon core and biofilm. The model considers that the reaction is performed in the biofilm and in the liquid phase and includes dye transport by dispersion and diffusion. The concentration profile within the bioparticles changes with reactor height and time as the equilibrium is achieved. Changes in dye concentrations affect the concentration profile in the reactor and reduce the removal efficiency. The effectiveness factor depends on the reactor height and on the dye concentration at the inlet.     

Different bioreactor configurations for the decolourisation of the azo dye reactive black 5 by Geotrichum sp. CCMI 1019

Decolourisation of the azo dye Reactive Black 5 by Geotrichum sp. CCMI 1019 was studied using stirred tank reactors (STR) and two types of bubble columns (porous plate (PP) bubble column and aeration tube (AT) bubble column). For the bubble columns, the k_La increased with the gas fractional hold-up (ε_G) and the aeration rate. A linear relationship between ε_G and superficial gas velocity was obtained for all reactors. At same aeration rates, the PP bubble columns showed higher k_La and hold-up values than the AT bubble column. In the STRs, large and dense aggregates were formed which adhered to surfaces whereas bubble columns gave smaller and less compact pellets.

Manganese peroxidase and laccase were detected in the extracellular media in all reactors. However, laccase was only detected after the onset of decolourisation, suggesting that additional enzymes may be involved. Mn peroxidase activity was detected (about 46 U/ml) in both the STRs and AT bubble columns but higher values (110 U/ml) were obtained with the PP bubble columns.

Out of the three reactor systems studied, the AT bubble columns gave the most favourable results for Reactive Black 5 decolourisation. Rapid and complete colour removal was obtained throughout the visible spectrum. Bubble columns are simple in design as well as operation and may be useful for the bioremediation of textile wastewater.     

Mechanism of enzymatic degradation of the azo dye Orange II determined by ex situ 1H nuclear magnetic resonance and electrospray ionization-ion trap mass spectrometry

Removal of azo dye effluents generated by textile photography industries is a main issue in wastewater treatment. Enzymatic treatment of dyes appears to be one of the most efficient processes for their degradation. The elucidation of degradation pathways is of special interest considering health and environmental priorities. Ex situ nuclear magnetic resonance (NMR) spectroscopy and electrospray ionization (ESI)-ion trap mass spectrometry performed directly on incubation medium have been used for the first time to follow kinetics of sulfonated azo dye Orange II enzymatic degradation. Nine transformation products were identified using these complementary analyses performed ex situ without any prior treatment. Three types of cleavage are proposed for the degradation pathway: (i) a symmetrical splitting of the azo linkage that leads to the formation of 4-aminobenzenesulfonate (and 1-amino-2-naphthol, not detected); (ii) an asymmetrical cleavage on the naphthalene side that generates 1,2-naphthoquinone and 4-diazoniumbenzenesulfonate as products, with the latter one being transformed into 4-hydroxybenzensulfonate; and (iii) a third degradation pathway that leads to 2-naphthol and 4-hydroxybenzenesulfonate. Moreover, three other intermediates have been identified. This study, which constitutes the first concomitant use of (1)H NMR spectroscopy and ESI-ion trap mass spectrometry in this field, illustrates the indubitable interest of the ex situ approach.     

Bioremediation potential of a widespread industrial biowaste as renewable and sustainable biosorbent for synthetic dye pollution

In this study, a model synthetic azo dye (Basic red 46) bioremoval by Carpinus betulus sawdust as inexpensive, eco-friendly, and sustainable biosorbent from aqueous solution was examined in a batch biosorption system. The effective environmental parameters on the biosorption process, such as the value of pH, amount of biosorbent, initial dye concentration and contact time were optimized using classical test design. The possible dye-biosorbent interaction was determined by Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). The equilibrium, thermodynamic, and kinetic studies for the biosorption of Basic red 46 onto the sawdust biomass were performed. In addition, a single-stage batch dye biosorption system was also designed. The dye biosorption yield of biosorbent was significantly influenced by the change of operating variables. The experimental data were best described by the Freundlich isotherm model and both the pseudo-first-order kinetic and the pseudo-second-order kinetic models. Thermodynamic research indicated that the biosorption of dye was feasible and spontaneous. Based on the Langmuir isotherm model, the biosorbent was found to have a maximum biosorption potential higher than many other biosorbents in the literature (264.915?mg g^?1). Thus, this investigation presents a novel green option for the assessment of waste sawdust biomass as a cheap and effective biosorbent material.