Decolorisation, biodegradation and detoxification of benzidine based azo dye

Phycoremediation of textile effluents with enhanced efficacy of biodiesel production by algae and potential use of remediated effluent for improving growth of wheat

The uncontrolled industrialization and unrestricted textile production combined with inappropriate effluent treatment services in developing countries like Pakistan have multiplied the number of harmful effluent discharge. These effluents are enriched with dyes, heavy metal ions, and other hazardous materials that are poisonous and carcinogenic to living organisms. For that reason, the utilization of economic and efficient control techniques against such pollutants is imperative to protect natural resources. The triple algal role for phycoremediation of textile effluent was utilized in this study to make it suitable for irrigation and higher biofuel production. Locally isolated two strains, CKW1 (Spirogyra sp.) and PKS33 (Cladophora sp.), were used to treat the effluent collected from the direct outlets of the textile industries. The treated effluent was then tested for its toxicity and applied to wheat at initial stage grown under axenic conditions to check its effect on wheat (Triticum aestivum L.) vegetative growth and development. Finally, the algal biomass obtained after treatment was subjected to trans-esterification for predicting the amount of biodiesel production. Study outcomes revealed that the algal strains were able to decolorize the effluent entirely within 96-120 h. Compared to un-treated textile effluent, the phycoremediated wastewater application to wheat plants enhanced the plant biomass by 80%. Lastly, the production of biodiesel from algal biomass attained after phycoremediation was 35% less to algal biomass obtained under normal growth conditions. It can be concluded that the algal use helps to treat the contaminated effluent and marks them re-usable for irrigating plants and producing biomass which could be utilized for biodiesel production.

Valorizing lignin-like dyes and textile dyeing wastewater by a newly constructed lipid-producing and lignin modifying oleaginous yeast consortium valued for biodiesel and bioremediation

Construction of a multipurpose yeast consortium suitable for lipid production, textile dye/effluent removal and lignin valorization is critical for both biorefinery and bioremediation. Therefore, a novel oleaginous consortium, designated as OYC-Y.BC.SH has been developed using three yeast cultures viz. Yarrowia sp. SSA1642, Barnettozyma californica SSA1518 and Sterigmatomyces halophilus SSA1511. The OYC-Y.BC.SH was able to grow on different carbon sources and accumulate lipids, with its highest lipid productivity (1.56 g/L/day) and lipase activity (170.3 U/mL) exhibited in xylose. The total saturated fatty acid content was 36.09 %, while the mono-unsaturated and poly-unsaturated fatty acids were 45.44 and 18.30 %, respectively, making OYC-Y.BC.SH valuable for biodiesel production. The OYC-Y.BC.SH showed its highest decolorization efficiency of Red HE3B dye (above 82 %) in presence of sorghum husk as agricultural co-substrate, suggesting its feasibility for simultaneous lignin valorization. The significant higher performance of OYC-Y.BC.SH on decolorizing the real dyeing effluent sample at pH 8.0 suggests its potential and suitability for degrading most of the wastewater textile effluents. Clearly, toxicological studies underline the additional advantage of using OYC-Y.BC.SH for bioremediation of industrial dyeing effluents in terms of decolorization and detoxification. A possible mechanism of Red HE3B biodegradation and ATP synthesis was also proposed.

Accelerated azo dye degradation and concurrent hydrogen production in the single-chamber photocatalytic microbial electrolysis cell

The single-chamber microbial electrolysis cell constructed with a TiO₂-coated photocathode, termed photocatalytic microbial electrolysis cell (PMEC), was developed to accelerate methyl orange (MO) degradation and concurrent hydrogen (H₂) recovery under UV irradiation. Results showed that faster MO decolorization rates were achieved from the PMEC compared with those without UV irradiation or with open circuit. With increase of MO concentrations (acetate as co-substrate) from 50 to 300mg/L at an applied voltage of 0.8V, decolorization efficiencies decreased from 98% to 76% within 12h, and cyclic H₂ production declined from 113 to 68mL. As the possible mechanism of MO degradation, bioelectrochemical reduction, co-metabolism reduction, and photocatalysis were involved; and degradation intermediates (mainly sulfanilic acid and N,N-dimethylaniline) were further degraded by OH generated from photocatalysis. This makes MO mineralization be possible in the single-chamber PMEC. Hence, the PMEC is a promising system for dyeing wastewater treatment and simultaneous H₂ production.

Catalytic degradation of Acid Orange 7 with hydrogen peroxide using CoxOy-N/GAC catalysts in a bicarbonate aqueous solution

The cobalt-based catalysts CoxOy-N/GAC were prepared by pyrolysis of a cobalt–phenanthroline complex on granular active carbon in nitrogen atmosphere, and tested for the degradation of Acid Orange 7 with H₂O₂ in a bicarbonate aqueous solution.

Biodecolorization and biodegradation of reactive Levafix Blue E-RA granulate dye by the white rot fungus Irpex lacteus

The treatment of effluents from textile industry with microorganisms, especially bacteria and fungi, has recently gained attention. The present study was conducted using white rot fungi Irpex lacteus, Trametes hirsuta, Trametes sp., and Lentinula edodes for the decolorization of reactive textile Levafix Blue E-RA granulate dye. I. lacteus resulted in the best decolorization and degradation of the dye within four days. Therefore, more detailed studies were carried out using I. lacteus. The decolorization was evaluated at various concentration, pH values, and temperatures. The activities of laccase, manganese peroxidase, and lignin peroxidase enzymes were estimated to reveal the roles of enzymes in decolorization. The colorless nature of the fungal cells revealed that decolorization occurred through degradation, and confirmed by analysis of the metabolites by UV-visible spectroscopy and High Performance Liquid Chromatography after decolorization. The metabolites were identified by Gas Chromatography-Mass Spectrometry, and functional group analysis was performed by Fourier Transform Infrared Spectroscopy. The degraded dye metabolites were assessed for phytotoxicity using Vigna radiata and Brassica juncea, which demonstrated nontoxic nature of the metabolites formed after degradation of dye.

Decolorization and degradation of azo dye--Reactive Violet 5R by an acclimatized indigenous bacterial mixed cultures-SB4 isolated from anthropogenic dye contaminated soil

Azo dyes an important group of synthetic compounds are recalcitrant xenobiotics. Conventional technologies are unsuccessful to efficiently remove these compounds from contaminated environment. However, consorted metabolic functioning of innate microbial communities is a promising approach for bioremediation of polluted environment. Bacterial mixed cultures SB4 proficient in complete decolorization of azo dye - Reactive Violet 5R was developed through culture enrichment technique. Bacterial community composition based on 16S rRNA gene analysis revealed that mixed cultures SB4 composed of six bacterial strains namely Bacillus sp. V1DMK, Lysinibacillus sp. V3DMK, Bacillus sp. V5DMK, Bacillus sp. V7DMK, Ochrobacterium sp. V10DMK, Bacillus sp. V12DMK. SB4 grew well in minimal medium containing low amount of glucose and yeast extract (YE) (1 g/L) and decolorized 200mg/L of RV5 within 18 h under static condition. Mixed cultures SB4 decolorized wide range of azo dyes and maximum rate of decolorization was observed at 37 °C and pH 7.0. Decolorization efficiency was found to be unaltered under high RV5 and salt concentration where 1500 mg/L of RV5 was decolorized in presence of 20 g/L NaCl. We propose the asymmetric cleavage of RV5 and Fourier transformed infrared (FTIR), NMR and gas chromatography-mass spectrometry (GC-MS) confirmed the formation of four intermediatory compounds 1-diazo-2-naphthol, 4-hydroxybenzenesulphonic acid, 2-naphthol and benzenesulphonic acid.

Decolorization and biodegradation of azo dye, reactive blue 59 by aerobic granules

The present study deals with development of aerobic granules from textile wastewater sludge and challenged with different concentration of reactive blue 59 (RB59) to test their dye degradation potential. The granules efficiently degraded reactive blue 59 and also sustained higher dye loading of up to 5.0 g l(-1). The significant induction of enzymes azoreductase and cytochrome P-450 indicated their prominent role in the dye degradation while genotoxicity studies demonstrated that the biotransformed product of the dye as non-toxic. The microbial community of the textile dyes degrading aerobic sludge granules analyzed by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE), revealed significantly diverse dye degrading microbial community belonging to alpha-, beta-, and gamma-proteobacteria.

Decolorization of textile dyes by Alishewanella sp. KMK6

Alishewanella sp. strain KMK6 was isolated from textile dye-contaminated soil. The strain was able to decolorize and degrade different azo dyes and displayed high dye degradation ability and tolerance. The bacterium could completely degrade 2.5 g l(-1) dye, Reactive Blue 59 within 6 h. The induction in the level of cytochrome P-450 and activities of azoreductase and NADH-dichlorophenolindophenol reductase were observed in the cells after dye decolorization indicating the role of these enzymes. The intermediates of Reactive Blue 59 degradation were identified by high-performance liquid chromatography, gas chromatography and mass spectroscopy, and Fourier transform infrared spectroscopy. The ecotoxicity has been evaluated for dye and its metabolites by 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (a yellow tetrazole) and comet assay, and it revealed that the dye degradation products were nontoxic.

Post-treatment of anaerobically degraded azo dye Acid Red 18 using aerobic moving bed biofilm process: enhanced removal of aromatic amines

The application of aerobic moving bed biofilm process as post-treatment of anaerobically degraded azo dye Acid Red 18 was investigated in this study. The main objective of this work was to enhance removal of anaerobically formed the dye aromatic metabolites. Three separate sequential treatment systems were operated with different initial dye concentrations of 100, 500 and 1000 mg/L. Each treatment system consisted of an anaerobic sequencing batch reactor (An-SBR) followed by an aerobic moving bed sequencing batch biofilm reactor (MB-SBBR). Up to 98% of the dye decolorization and more than 80% of the COD removal occurred anaerobically. The obtained results suggested no significant difference in COD removal as well as the dye decolorization efficiency using three An-SBRs receiving different initial dye concentrations. Monitoring the dye metabolites through HPLC suggested that more than 80% of anaerobically formed 1-naphthylamine-4-sulfonate was completely removed in the aerobic biofilm reactors. Based on COD analysis results, at least 65-72% of the dye total metabolites were mineralized during the applied treatment systems. According to the measured biofilm mass and also based on respiration-inhibition test results, increasing the initial dye concentration inhibited the growth and final mass of the attached-growth biofilm in MB-SBBRs.

Ecofriendly biodegradation and detoxification of Reactive Red 2 textile dye by newly isolated Pseudomonas sp. SUK1

The aim of this work is to evaluate textile dyes degradation by novel bacterial strain isolated from the waste disposal sites of local textile industries. Detailed taxonomic studies identified the organisms as Pseudomonas species and designated as strain Pseudomonas sp. SUK1. The isolate was able to decolorize sulfonated azo dye (Reactive Red 2) in a wide range (up to 5 g l(-1)), at temperature 30 degrees C, and pH range 6.2-7.5 in static condition. This isolate also showed decolorization of the media containing a mixture of dyes. Measurements of COD were done at regular intervals to have an idea of mineralization, showing 52% reduction in the COD within 24h. Induction in the activity of lignin peroxidase and azoreductase was observed during decolorization of Reactive Red 2 in the batch culture, which represented their role in degradation. The biodegradation was monitored by UV-vis, IR spectroscopy, HPLC. The final product, 2-naphthol was characterized by GC-mass spectroscopy. The phytotoxicity study revealed the degradation of Reactive Red 2 into non-toxic product by Pseudomonas sp. SUK1.

Biodegradation and detoxification of reactive textile dye by isolated Pseudomonas sp. SUK1

An isolated bacterium from a textile disposal site, Pseudomonas sp. SUK1, has the ability to decolorize the reactive textile dyes and methyl orange. This bacterium showed the potential to decolorize the textile dye Reactive Blue 59 at a high concentration (5 g/L(-1)), which is frequently used in the textile industry of Solapur, India. Induction in the activities of lignin peroxidase, azoreductase, and dichlorophenol indophenol reductase was observed during the decolorization of Methyl Orange and Reactive Blue 59. Methyl Orange (as model azo dye) was used to understand the mechanism of biodegradation by Pseudomonas sp. SUK1. The final product was identified as 1,4-benzenediamine, N, N-dimethyl by gas chromatography-mass spectroscopy. Microbial and phytotoxicity studies revealed the nontoxic nature of the products of Reactive Blue 59.

Detoxification of benzidine-based azo dye by E. gallinarum: time-course study

Direct black 38 (DB38) dye is a well-established toxic and carcinogenic compound. Present investigation reports isolation of an Enterococcus gallinarum strain capable of decolorizing and degrading it. Changes in toxicity and mutagenicity of DB38 and its metabolites were also determined using a battery of carefully selected tests (cytotoxicity, respiration inhibition test and Ames test). Toxicity assays were carried out on E. gallinarum itself as this also gave information about suitability of this strain for the dye decolorization operation. The strain was found to reduce both toxicity and mutagenicity of DB38 metabolites. Benzidine and 4-aminobiphenyl (4-ABP) were identified as the DB38 metabolites, responsible for its toxic and mutagenic properties, by HPLC-MS analysis. Further degradation of benzidine and 4-ABP was found to result in the decrease in toxicity and mutagenicity.

Biological decolourization of C.I. Direct Black 38 by E. gallinarum

In the present study, an Enterococcus gallinarum strain was isolated from effluent treatment plant of a textile industry based on its ability to decolourize C.I. Direct Black 38 (DB38), a benzidine-based azo dye. Effects of dye concentration and medium composition on dye decolourization were studied. The strain was found to decolourize DB38 even under aerobic conditions. Kinetics of DB38 decolourization was also examined, and V(max) and K(s) of decolourization were found to be higher in Luria broth (12.8 mg l(-1)h(-1) and 490.6 mg l(-1)) than in minimal medium (4.09 mg l(-1)h(-1) and 161.84 mg l(-1)). However, decolourization rate/biomass was found to be higher in minimal medium than in Luria broth, indicating greater decolourization efficiency of biomass in the former. The study also revealed biodegradation of DB38 to benzidine and its further deamination to 4-aminobiphenyl (4-ABP) by the culture. Ammonia released during this process was used as nitrogen source for growth of the culture.

Biodegradation of reactive textile dye Red BLI by an isolated bacterium Pseudomonas sp. SUK1

A novel bacterial strain capable of decolorizing reactive textile dye Red BLI is isolated from the soil sample collected from contaminated sites of textile industry from Solapur, India. The bacterial isolate was identified as Pseudomonas sp. SUK1 on the basis of 16S rDNA analysis. The Pseudomonas sp. SUK1 decolorized Red BLI (50 mg l(-1)) 99.28% within 1h under static anoxic condition at pH range from 6.5 to 7.0 and 30 degrees C. This strain has ability to decolorize various reactive textile dyes. UV-Vis spectroscopy, FTIR and TLC analysis of samples before and after dye decolorization in culture medium confirmed decolorization of Red BLI. A significant increase in the activities of aminopyrine N-demethylase and NADH-DCIP reductase in cells obtained after decolorization indicates involvement of these enzymes in the decolorization process. Phytotoxicity testing with the seeds of Sorghum vulgare and Phaseolus mungo, showed more sensitivity towards the dye, while the products obtained after dye decolorization does not have any inhibitory effects.

Decolorisation and detoxification of Direct Blue-15 by a bacterial consortium

Studies were carried out on decolorisation and biotransformation of the dye Direct Blue-15 into 3,3'-dimethoxybenzidine (O'-dianisidine) and a sulphonated derivative by a five-member bacterial consortium. Chromatographic studies revealed further complete biodegradation of 3,3'-dimethoxybenzidine coupled with release of ammonia, but the recalcitrant sulphonated derivative persisted. The microorganisms identified in the mixed consortium by 16S rDNA sequence analysis were Alcaligenes faecalis, Sphingomonas sp. EBD, Bacillus subtilis, Bacillus thuringiensis and Enterobacter cancerogenus. The cytotoxicity data showed a significant reduction in the toxicity (P<0.001) of the degraded dye as evidenced from the number of viable human polymorphonuclear leukocyte cells present.

Biodegradation of textile azo dye by Shewanella decolorationis 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 H(2)S 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.

Biodegradation of benzidine based dye Direct Blue-6 by Pseudomonas desmolyticum NCIM 2112

Pseudomonas desmolyticum NCIM 2112 was able to degrade a diazo dye Direct Blue-6 (100 mg l(-1)) completely within 72 h of incubation with 88.95% reduction in COD in static anoxic condition. Induction in the activity of oxidative enzymes (LiP, laccase) and tyrosinase while decolorization in the batch culture represents their role in degradation. Dye also induced the activity of aminopyrine N-demethylase, one of the enzyme of mixed function oxidase system. The biodegradation was monitored by UV-Vis, IR spectroscopy and HPLC. The final products, 4-amino naphthalene and amino naphthalene sulfonic acid were characterized by GC-mass spectroscopy.

Kinetics of decolourisation and biotransformation of direct black 38 by C. hominis and P. stutzeri

In the present study, a consortium of Cardiobacterium hominis and Pseudomonas stutzeri was isolated from an effluent treatment plant of a textile industry, based on its ability to decolourise azo dyes including direct black 38 (DB38), a benzidine-based azo dye. The role of each culture in the decolourisation process was elucidated, and C. hominis was found to decolourise the dye. Although P. stutzeri could not decolourise the dye, it was found to synergistically enhance dye decolourisation activity of C. hominis by scavenging oxygen in the medium and creating an anaerobic condition (oxidation/reduction potential -440 mV), which is known to be necessary for azo dye decolourisation. Together, the cultures could decolourise 90.5% of 100 mg l(-1) DB38 within 24 h. Kinetics of DB38 decolourisation was also examined, and P. stutzeri was found to increase V (max) and K (m) of decolourisation activity of C. hominis by 3.6- and 3-fold, respectively. The study also revealed a pathway of DB38 degradation with the release of benzidine from DB38 and subsequent degradation of benzidine to 4-aminobiphenyl by the cultures.