Degradation analysis of Reactive Red 198 by hairy roots of <Emphasis Type="Italic">Tagetes patula</Emphasis> L. (Marigold)

Tagetes patula L. (Marigold) hairy roots were selected among few hairy root cultures from other plants tested for the decolorization of Reactive Red 198. Hairy roots of Tagetes were able to remove dye concentrations up to 110 mg L^−l and could be successively used at least for five consecutive decolorization cycles. The hairy roots of Tagetes decolorized six different dyes, viz. Golden Yellow HER, Methyl Orange, Orange M2RL, Navy Blue HE2R, Reactive Red M5B and Reactive Red 198. Significant induction of the activity of biotransformation enzymes indicated their crucial role in the dye metabolism. UV–vis spectroscopy, HPLC and FTIR spectroscopy analyses confirmed the degradation of Reactive Red 198. A possible pathway for the biodegradation of Reactive Red 198 has been proposed with the help of GC–MS and metabolites identified as 2-aminonaphthol, p-aminovinylsulfone ethyl disulfate and 1-aminotriazine, 3-pyridine sulfonic acid. The phytotoxicity study demonstrated the non-toxic nature of the extracted metabolites. The use of such hairy root cultures with a high ability for bioremediation of dyes is discussed.     

Decolorization and detoxification of Congo red and textile industry effluent by an isolated bacterium <Emphasis Type="Italic">Pseudomonas</Emphasis> sp. SU-EBT

The 16S rRNA sequence and biochemical characteristics revealed the isolated organism as Pseudomonas sp. SU-EBT. This strain showed 97 and 90% decolorization of a recalcitrant dye, Congo red (100 mg l⁻¹) and textile industry effluent with 50% reduction in COD within 12 and 60 h, respectively. The optimum pH and temperature for the decolorization was 8.0 and 40°C, respectively. Pseudomonas sp. SU-EBT was found to tolerate the dye concentration up to 1.0 g l⁻¹. Significant induction in the activity of intracellular laccase suggested its involvement in the decolorization of Congo red. The metabolites formed after decolorization of Congo red, such as p-dihydroxy biphenyl, 8-amino naphthol 3-sulfonic acid and 3-hydroperoxy 8-nitrosonaphthol were characterized using FTIR and GC–MS. Phytotoxicity study revealed nontoxic nature of the degradation metabolites to Sorghum bicolor, Vigna radiata, Lens culinaris and Oryza sativa plants as compared to Congo red and textile industry effluent. Pseudomonas sp. SU-EBT decolorized several individual textile dyes, dye mixtures and textile industry effluent, thus it is a useful strain for the development of effluent treatment methods in textile processing industries.     

Significant reduction in toxicity,BOD, and COD of textile dyes and textile industry effluent by a novel bacterium <Emphasis Type="Italic">Pseudomonas</Emphasis> sp. LBC1

The 16S rRNA sequence analysis and biochemical characteristics were confirmed that the isolated bacterium is Pseudomonas sp. LBC1. The commonly used textile dye, Direct Brown MR has been used to study the fate of biodegradation. Pseudomonas sp. LBC1 showed 90% decolorization of Direct Brown MR (100 mg/L) and textile industry effluent with significant reduction in COD and BOD. The optimum condition for decolorization was 7.0 pH and 40°C. Significant increase in a activity of extracellular laccase suggested their possible involvement in decolorization of Direct Brown MR. Biodegradation metabolites viz. 3,6-dihydroxy benzoic acid, 2-hydroxy-7-aminonaphthol-3-sulfonic acid, and p-dihydroperoxybenzene were identified on the basis of mass spectra and using the 1.10 beta Shimadzu NIST GC–MS library. The Direct Brown MR and textile industry effluent were toxic to Sorghum bicolor and Vigna radiata plants as compared to metabolites obtained after decolorization. The Pseudomonas sp. LBC1 could be useful strain for decolorization and detoxification of textile dyes as well as textile industry effluent.     

Decolorization of Acid red 151 by Aspergillus niger SA1 under different physicochemical conditions

The fungal strain A. niger SA1 isolated from textile wastewater pond proved to be an important source of remediation (decolorization/degradation) for textile dye, AR 151 (Reactive diazo dye) under different physicochemical conditions. Decolorization assays of AR 151 were carried out in Simulated textile effluent under shake flask condition for 8 days. Decolorization (at 20 mg l⁻¹ of dye) and related biomass production overall decreased with increase in pH from 5 to 9, at 30°C. It was maximum (95.71%) at pH 5 with highest amount of three residual products (36.91 (α-naphthol = 5.72) (sulfanilic acid = 24.81) (aniline = 6.38)) besides 2.05 mg ml⁻¹ of biomass production at an optimum concentration 6 and 0.1 mg l⁻¹ of glucose and urea respectively. The formation of the three products followed a quite different pattern at different pH values, however, it was considerably low (Total = 2.81 mg l⁻¹) compared to the amount of decolorization (67.26%) at pH 8. Decolorization (95–97%) was most favored under mesophilic temperature (25–45°C). It increased i.e., 90–98% with subsequent increase in dye from 10 to 100 mg l⁻¹, kept ≥50% below 400 mg l⁻¹ and drastically declined to 17% at 500 mg l⁻¹ of dye. Apparently, decolorization is found to be associated with fungal growth and hyphal uptake mechanism (Biosorption/Bioadsorption), however, mineralization of AR 151 and related products under different operational conditions also suggested a metabolically mediated decolorization/degradation.     

Decolorization of structurally different textile dyes by Aspergillus niger SA1

The fungal strain, Aspergillus niger SA1, isolated from textile wastewater sludge was screened for its decolorization ability for four different textile dyes. It was initially adapted to higher concentration of dyes (10–1,000 mg l⁻¹) on solid culture medium after repeated sub-culturing. Maximum resistant level (mg l⁻¹) sustained by fungal strain against four dyes was in order of; Acid red 151 (850) > Orange II (650) > Drimarene blue K₂RL (550) > Sulfur black (500). The apparent dye removal for dyes was seen largely due to biosorption/bioadsorption into/onto the fungal biomass. Decolorization of Acid red 151, Orange II, Sulfur black and Drimarine blue K₂RL was 68.64 and 66.72, 43.23 and 44.52, 21.74 and 28.18, 39.45 and 9.33% in two different liquid media under static condition, whereas, it was 67.26, 78.08, 45.83 and 13.74% with 1.40, 1.73, 5.16 and 1.87 mg l⁻¹ of biomass production under shaking conditions respectively in 8 days. The residual amount (mg l⁻¹) of the three products (α-naphthol, sulfanilic acid and aniline) kept quite low i.e., ≤2 in case AR 151 and Or II under shaking conditions. Results clearly elucidated the role of Aspergillus niger SA1 in decolorizing/degrading structurally different dyes into basic constituents.     

Adhesion to the hydrocarbon phase increases phenanthrene degradation by <Emphasis Type="Italic">Pseudomonas fluorescens</Emphasis> LP6a

Microbial adhesion is an important factor that can influence biodegradation of poorly water soluble hydrocarbons such as phenanthrene. This study examined how adhesion to an oil–water interface, as mediated by 1-dodecanol, enhanced phenanthrene biodegradation by Pseudomonas fluorescens LP6a. Phenanthrene was dissolved in heptamethylnonane and added to the aerobic aqueous growth medium to form a two phase mixture. 1-Dodecanol was non-toxic and furthermore could be biodegraded slowly by this strain. The alcohol promoted adhesion of the bacterial cells to the oil–water interface without significantly changing the interfacial or surface tension. Introducing 1-dodecanol at concentrations from 217 to 4,100 mg l⁻¹ increased phenanthrene biodegradation by about 30% after 120 h incubation. After 100 h incubation, cultures initially containing 120 or 160 mg l⁻¹ 1-dodecanol had mineralized >10% of the phenanthrene whereas those incubated without 1-dodecanol had mineralized only 4.5%. The production and accumulation of putative phenanthrene metabolites in the aqueous phase of cultures likewise increased in response to the addition of 1-dodecanol. The results suggest that enhanced adhesion of bacterial cells to the oil–water interface was the main factor responsible for enhanced biodegradation of phenanthrene to presumed polar metabolites and to CO₂.     

Isolation and characterization of alkalotolerant <Emphasis Type="Italic">Pseudomonas</Emphasis> sp. strain ISTDF1 for degradation of dibenzofuran

An alkalotolerant Pseudomonas strain was enriched and isolated from effluent of the pulp and paper industry. This strain was able to degrade dibenzofuran and utilize it as a sole source of energy and carbon. The GC–MS based detection of various intermediary metabolites of biodegradation suggested the involvement of angular as well as lateral pathway of dibenzofuran biodegradation. The GC–MS based detection of various intermediary metabolites of biodegradation suggested the involvement of angular as well as lateral pathway of dibenzofuran biodegradation. This diverse dioxygenation property of the strain allowed it to utilize various recalcitrant chlorinated xenobiotics and PAHs compounds. This strain showed optimum utilization (~85%) of dibenzofuran (200 mg l⁻¹) within 36 h at pH 10 at 40°C. The growth of the strain was supported by a wide range of environmental conditions such as temperature, pH, and concentration of dibenzofuran, suggesting that it can be used for in situ bioremediation of dioxin-like compound.     

Evaluation of synthetic dye decolorization capacity in Ischnoderma resinosum

The little studied white rot fungus Ischnoderma resinosum was tested for its ability to decolorize seven different synthetic dyes. The strain efficiently decolorized Orange G, Amaranth, Remazol Brilliant Blue R, Cu-phthalocyanin and Poly R-478 on agar plates and in liquid culture at a relatively high concentration of 2–4 and 0.5–1 g l⁻¹, respectively. Malachite Green and Crystal Violet were decolorized to a lower extent up to the concentration of 0.1 g l⁻¹. Decolorization capacity of I. resinosum was higher than that in Phanerochaete chrysosporium, Pleurotus ostreatus or Trametes versicolor. In contrast with these thoroughly examined fungi, I. resinosum was able to degrade a wide spectrum of chemically and structurally different synthetic dyes. I. resinosum also efficiently decolorized dye mixtures. In liquid culture, Orange G and Remazol Brilliant Blue R were decolorized most rapidly; the process was not affected by different nitrogen content in the media. Shaken cultivation strongly inhibited the decolorization of Orange G.     

Decolorization of 1-aminoanthraquinone-2-sulfonic acid by Sphingomonas xenophaga

Sphingomonas xenophaga QYY from sludge samples could effectively decolorize 1-aminoanthraquinone-2-sulfonic acid (ASA-2), one kind of anthraquinone dye intermediate, under aerobic conditions. More than 98% of ASA-2 could be removed within 120 h at the dye concentration from 200 mg l⁻¹ to 1,000 mg l⁻¹ due to oxidative degradation. The strain converted ASA-2 to 2-(2′-hydroxy-3′-amino-4′-sulfo-benzoyl)-benzoic acid, 2-(2′-amino-3′-sulfo-6′-hydroxy-benzoyl)-benzoic acid, o-phthalic acid and 2-amino-3-hydroxy-benzenesulfonic acid, which were identified using HPLC-MS and NMR. A possible initial decolorization pathway was proposed according to these metabolites. The decolorization of ASA-2 by cells in the basal salt medium was induced by ASA-2, and was due to soluble cytosolic enzymes. Combined initial decolorization pathway and the analysis of decolorization enzyme(s), the major enzyme responsible for ASA-2 decolorization was a NADH-dependent oxygenase.     

Effects of Orange II and Sudan III azo dyes and their metabolites on <Emphasis Type="Italic">Staphylococcus aureus</Emphasis>

Azo dyes are widely used in the plastic, paper, cosmetics, food, and pharmaceutical industries. Some metabolites of these dyes are potentially genotoxic. The toxic effects of azo dyes and their potential reduction metabolites on Staphylococcus aureus ATCC BAA 1556 were studied. When the cultures were incubated with 6, 18, and 36 μg/ml of Orange II and Sudan III for 48 h, 76.3, 68.5, and 61.7% of Orange II and 97.8, 93.9, and 75.8% of Sudan III were reduced by the bacterium, respectively. In the presence of 36 μg/ml Sudan III, the cell viability of the bacterium decreased to 61.9% after 48 h of incubation, whereas the cell viability of the control culture without the dye was 71.5%. Moreover, the optical density of the bacterial cultures at 10 h decreased from 0.74 to 0.55, indicating that Sudan III is able to inhibit growth of the bacterium. However, Orange II had no significant effects on either cell growth or cell viability of the bacterium at the tested concentrations. 1-Amino-2-naphthol, a metabolite common to Orange II and Sudan III, was capable of inhibiting cell growth of the bacterium at 1 μg/ml and completely stopped bacterial cell growth at 24–48 μg/ml. On the other hand, the other metabolites of Orange II and Sudan III, namely sulfanilic acid, p-phenylenediamine, and aniline, showed no significant effects on cell growth. p-Phenylenediamine exhibited a synergistic effect with 1-amino-2-naphthol on cell growth inhibition. All of the dye metabolites had no significant effects on cell viability of the bacterium.     

Decolorization of textile dye by <Emphasis Type="Italic">Candida albicans</Emphasis> isolated from industrial effluents

The aim of the present work was to observe microbial decolorization and biodegradation of the Direct Violet 51 azo dye by Candida albicans isolated from industrial effluents and study the metabolites formed after degradation. C. albicans was used in the removal of the dye in order to further biosorption and biodegradation at different pH values in aqueous solutions. A comparative study of biodegradation analysis was carried out using UV–vis and FTIR spectroscopy, which revealed significant changes in peak positions when compared to the dye spectrum. Theses changes in dye structure appeared after 72 h at pH 2.50; after 240 h at pH 4.50; and after 280 h at pH 6.50, indicating the different by-products formed during the biodegradation process. Hence, the yeast C. albicans was able to remove the color substance, demonstrating a potential enzymatic capacity to modify the chemical structure of pigments found in industrial effluents.     

Isolation of a buprofezin co-metabolizing strain of <Emphasis Type="Italic">Pseudomonas</Emphasis> sp. DFS35-4 and identification of the buprofezin transformation pathway

Buprofezin is a widely used insecticide that has caused environmental pollution in many areas. However, biodegradation of buprofezin by pure cultures has not been extensively studied, and the transformation pathway of buprofezin remains unclear. In this paper, a buprofezin co-metabolizing strain of DFS35-4 was isolated from a buprofezin-polluted soil in China. Strain DFS35-4 was preliminarily identified as Pseudomonas sp. based on its morphological, physiological, and biochemical properties, as well as 16S rRNA gene analysis. In the presence of 2.0 g l⁻¹ sodium citrate, strain DFS35-4 degraded over 70% of 50 mg l⁻¹ buprofezin in 3 days. Strain DFS35-4 efficiently degraded buprofezin in the pH range of 5.0–10.0 and at temperatures between 20 and 30°C. Three metabolites, 2-imino-5-phenyl-3-(propan-2-yl)-1,3,5-thiadiazinan-4-one, 2-imino-5-phenyl-1,3,5-thiadiazinan-4-one, and methyl(phenyl) carbamic acid, were identified during the degradation of buprofezin using gas chromatography–mass spectrometry (GC–MS) and tandem mass spectrometry (MS/MS). A partial transformation pathway of buprofezin in Pseudomonas sp. DFS35-4 was proposed based on these metabolites.     

Concentration dependent growth/non-growth linked kinetics of endosulfan biodegradation by <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis>

The rates of biodegradation of endosulfan by P. aeruginosa were determined with different initial endosulfan concentrations (10, 50, 100, 150, 200 and 250 mg l⁻¹) and different growth linked kinetic models were fitted at these concentrations. At 10 mg endosulfan l⁻¹, Monod no growth model was well fitted. Monod with growth model described the biodegradation pattern at an initial concentration of 50, 100 and 150 mg endosulfan l⁻¹. Significant increases of P. aeruginosa MN2B14 density in broth culture during incubation further support this result. Conversely, zero order kinetic model was well fitted into the biodegradation data if initial endosulfan concentration was ≥200 mg endosulfan l⁻¹. The kinetics of endosulfan biodegradation by P. aeruginosa MN2B14 in liquid broth was highly dependent upon its initial concentration. The results of this study could be employed for predicting the persistence of endosulfan in water environment containing P. aeruginosa as an endosulfan degrading bacterium.     

Microbial decolorization of reactive black-5 in a two-stage anaerobic–aerobic reactor using acclimatized activated textile sludge

A two-stage anaerobic–aerobic treatment process based on mixed culture of bacteria isolated from textile dye effluent was used to degrade reactive black 5 dye (RB-5). The anaerobic step was studied in more detail by varying the dye concentration from 100 to 3000 mg l⁻¹. The results showed that major decolorization was achieved during the anaerobic process. The time required for decolorization by > 90% increased as the concentration of the dye increased. It was also found that maintaining dissolved oxygen (DO) concentration below 0.5 mg l⁻¹ and addition of a co-substrate viz., glucose, facilitates anaerobic decolorization reaction remarkably. An attempt was made to identify the metabolites formed in anaerobic process by using high performance liquid chromatography (HPLC) and UV–VIS spectrophotometry. A plate assay was performed for the detection of dominant decolorizing bacteria. Only a few bacterial colonies with high clearing zones (decolorization zones) were found. The results showed that under anaerobic condition RB-5 molecules were reduced and aromatic amines were generated. The aromatic amine metabolite was partly removed in subsequent aerobic bio-treatment. It was possible to achieve more than 90% decolorization and approximately 46% reduction in amine metabolite concentration through two-stage anaerobic–aerobic treatment after a reaction period of 2 days.     

Decolorization of azo dyes by <Emphasis Type="Italic">Shewanella oneidensis</Emphasis> MR-1 in the presence of humic acids

The effects of humic acid (HA) on azo dye decolorization by Shewanella oneidensis MR-1 were studied. It was found that HA species isolated from different sources could all accelerate the decolorization of Acid Red 27 (AR27). Anoxic and anaerobic conditions were required for the enhancement of azo dye decolorization by HA. In the presence of 50 mg DOC L⁻¹ Aldrich HA, 15–29% increases in decolorization efficiencies of azo dyes with different structures were achieved in 11 h. The enhancing effects increased with the increase of HA concentrations ranging from 25 to 150 mg DOC L⁻¹, and the decolorization rates were directly proportional to the HA concentrations when they were below 100 mg DOC L⁻¹. Lactate and formate were good electron donors for AR27 decolorization in the presence of HA. Both nitrate (0.1–3.0 mM) and nitrite (0.3–1.2 mM) inhibited AR27 decolorization in the presence of HA, and negligible decolorization was observed before their removal. Soluble FeCl₃ could accelerate the decolorization process in the presence of HA, whereas insoluble hematite could not. These findings may affect the understanding of bioremediation of azo dye-polluted environments and help improve the treatment of azo dye wastewaters.     

Decolorization of Acid Orange 7 by bacteria of different tinctorial type: a comparative study

The abilities of two bacterial strains of opposite tinctorial type, the Gram-negative Alcaligenes faecalis and the Gram-positive Rhodococcus erythropolis, to decolorize reaction medium containing initially 10, 50, 100, 200 and 500 mg l⁻¹ of the monoazo dye Acid Orange 7 are discussed. The dye-binding properties of the strains and the starting rate of the decolorization reaction in dependence on the initial dye concentration are compared. An assumption is made that the higher dye-binding ability of A. faecalis is due to the existence of an outer membrane. The experimental data revealed relative independence of the decolorization dynamics on the dye-binding properties of the cell, which could be regarded as an indirect confirmation of the known extracellular redox-mediator-dependent mechanism of azo group reduction.     

Isolation and characterization of <Emphasis Type="Italic">Pseudomonas</Emphasis> sp. DX7 capable of degrading sulfadoxine

Given that the intensive application of sulfonamides in aquaculture, animal husbandry and malaria treatment has lead to an increase in sulfonamide discharge into the environment, there is an increasing need to find a way to remediate sulfonamide-contaminated sites. The bacterial strain DX7 was isolated from a marine environment and is capable of degrading sulfadoxine. DX7 was identified as a Pseudomonas sp. based on 16S rRNA gene sequencing. Approximately 30% of sulfadoxine was degraded after Pseudomonas sp. DX7 was inoculated into mineral salt plus tryptone media containing 10 mg l⁻¹ sulfadoxine for 2 days. The degradation efficiency under different environmental conditions was characterized using HPLC. The optimal temperature and pH for sulfadoxine biodegradation were around 30°C and 6.0, respectively. The optimal concentrations of sulfadoxine and tryptone for sulfadoxine biodegradation were determined to be approximately 30 mg l⁻¹ and between 2.0 and 8.0 g l⁻¹, respectively. Cytotoxicity analysis indicated that the metabolites of sulfadoxine generated by Pseudomonas sp. DX7 showed significantly reduced cytotoxicity to Hela cells. These results suggest that Pseudomonas sp. DX7 is a new bacterial resource for degrading sulfadoxine and indicate the potential of the isolated strain in the bioremediation of sulfadoxine-contaminated environments.     

Decolorization of Azo Dye (Orange MR) by an Autochthonous Bacterium, <Emphasis Type="Italic">Micrococcus</Emphasis> sp. DBS 2

Soil and sediment samples obtained from Orange MR dye contaminated habitat were screened for heterotrophic bacterial population. The heterotrophic bacterial density of dye-contaminated soil was 2.14 × 10⁶ CFU/g. The generic composition of heterotrophic bacterial population was primarily composed of 10% of Proteus sp., 15% Aeromonas sp., 20% Bacillus sp., 25% Pseudomonas sp. and 30% Micrococcus sp. The bacterial strain that decolorized the azo dye Orange MR up to 900 ppm was identified as Micrococcus sp. The optimum inoculum load, pH and temperature were found to be 5%, 6 and 35°C, respectively. The rate of decolorization was assessed using spectrophotometer at 530 nm and the percentage of decolorization was ascertained. The autochthonous bacterial isolate was able to utilize the dye as both nitrogen and carbon source.     

Bacterial Decolorization of Azo Dyes by Rhodopseudomonas palustris

Summary The ability of Rhodopseudomonas palustris AS1.2352 possessing azoreductase activity to decolorize azo dyes was investigated. It was demonstrated that anaerobic conditions were necessary for bacterial decolorization, and the optimal pH and temperature were pH 8 and 30–35 °C, respectively. Decolorization of dyes with different molecular structures was performed to compare their degradability. The strain could decolorize azo dye up to 1250 mg l⁻¹, and the correlation between the specific decolorization rate and dye concentration could be described by Michaelis–Menten kinetics. Long-term repeated operations showed that the strain was stable and efficient during five runs. Cell extracts from the strain demonstrated oxygen-insensitive azoreductase activity in vitro.     

Biodegradation of phenol and 4-chlorophenol by the yeast <Emphasis Type="Italic">Candida tropicalis</Emphasis>

Biodegradation of phenol and 4-chlorophenol (4-cp) using a pure culture of Candida tropicalis was studied. The results showed that C. tropicalis could degrade 2,000 mg l⁻¹ phenol alone and 350 mg l⁻¹ 4-cp alone within 66 and 55 h, respectively. The capacity of the strain to degrade phenol was obviously higher than that to degrade 4-cp. In the dual-substrate system, 4-cp intensely inhibited phenol biodegradation. Phenol beyond 800 mg l⁻¹ could not be degraded in the presence of 350 mg l⁻¹ 4-cp. Comparatively, low-concentration phenol from 100 to 600 mg l⁻¹ supplied a sole carbon and energy source for C. tropicalis in the initial phase of biodegradation and accelerated the assimilation of 4-cp, which resulted in the fact that 4-cp biodegradation velocity was higher than that without phenol. And the capacity of C. tropicalis to degrade 4-cp was increased up to 420 mg l⁻¹ with the presence of 100–160 mg l⁻¹ phenol. In addition, the intrinsic kinetics of cell growth and substrate degradation were investigated with phenol and 4-cp as single and mixed substrates in batch cultures. The results illustrated that the models proposed adequately described the dynamic behaviors of biodegradation by C. tropicalis.