Microbial decolorization of azo dyes and dye industry effluent by Fomes lividus

The white rot fungus, Fomes lividus, was isolated from the logs of Shorea robusta in the Western Ghats region of Tamil Nadu, India. The fungus was tested for decolorization of azo dyes such as orange G (50 M) congo red (50 M) amido black 10B (25 M) and also for colour removal from dye industry effluents. The results revealed that the fungus could remove only 30.8% of orange G in the synthetic solution, whereas congo red and amido black 10B were removed by 74.0 and 98.9% respectively. A dye industry effluent was treated by the fungus in batch and continuous mode. In batch mode treatment, a maximum decolorization of 84.4% was achieved on day 4, and in continuous mode a maximum decolorization of 37.5% was obtained on day 5. The colour removal by the basidiomycete fungus might be due to adsorption of the dyes to the mycelial surface and metabolic breakdown. These results suggested that the batch mode treatment of Fomes lividus is one of the most efficient ways for colour removal in dye industry effluents.     

Hologram and 3D-quantitative structure toxicity relationship studies of azo dyes

Amino azobenzenes are important dyes in the food and textile industry but their application is limited due to their mutagenicity. Computational modeling techniques were used to help understand the factors responsible for mutagenicity, and several quantitative structure toxicity relationship (QSTR) models have been derived. HQSTR (hologram QSTR) analyses indicated that different substituents at sites on both rings contribute to mutagenicity. Fragment parameters such as bond (B) and connectivity(C), as well as donor-acceptor (DA)-based model provide significant results (q² = 0.59, r² = 0.92, ) explaining these harmful effect. HQSTR results indicated that a bulky group at ring “Y” and small group at ring “X” might help to decrease mutagenicity. 3D-QSTR based on comparative molecular field analyses (CoMFA) and comparative molecular similarity index analyses (CoMSIA) are also in agreement with HQSTR. The 3D QSTR studies reveal that steric and electrostatic field effects have a strong relationship with mutagenicity (for CoMFA: q² = 0.51, r² = 0.95, and for CoMSIA: q² = 0.51, r² = 0.93 and ). In summary, negative groups and steric bulk at ring “Y” and small groups at carbon-3 of ring “X” might be helpful in reducing the mutagenicity of azo dyes.     

Light-induced storage in layer-by-layer films of chitosan and an azo dye

The buildup of layer-by-layer (LBL) films from chitosan and the azodye Ponceau-S (PS) was investigated under various experimental conditions, and the resulting films were used in optical storage experiments. The kinetics for the writing process in optical storage was faster for LBL films prepared at low pHs, probably because the films had a larger free volume for isomerization of the chromophores. The nanostructured nature of the LBL films also affected the crystallinity of chitosan, which was considerably decreased in this type of film as chitosan became protonated because of the electrostatic interactions between adjacent layers.     

Decolorization of azo dyes and simulated dye bath wastewater using acclimatized microbial consortium--biostimulation and halo tolerance

Anaerobic acclimatization of activated sludge from a textile effluent treatment plant to high concentration of RB5 could effectively decolorize RB5 dye solution. The strains viz. Pseudomonas aeruginosa and Bacillus circulans and other unidentified laboratory isolates (NAD1 and NAD6) were predominantly present in the microbial consortium. The conditions for efficient decolorization, biostimulation to increase effectiveness of microbial consortium, its tolerance to high salt concentration and non-specific ability towards decolorization of eight azo dyes, are reported. The optimum inoculums concentration for maximum decolorization were found to be 1-5 ml of 1800+/-50 mg l(-1) MLSS and 37 degrees C, respectively. The decolorization efficiency was 70-90% during 48 h. The biomass showed efficient decolorization even in the presence of 10% NaCl, as tested with RB5. In the presence of flavin adenine dinucleotide (FAD) more than 99% decolorization occurred in 8h. The decolorization of RB5 was traced to extracellular enzymes. The effectiveness of acclimatized biomass under optimized conditions towards decolorization of two types of synthetic dye bath wastewaters that were prepared using chosen azo dyes is reported.     

'Naturalization' of textile disperse dyes through glycoconjugation: the case of a bis(2-hydroxyethyl) group containing azo dye

A family of five strictly related glycoconjugated azo dyes (GADs), characterized by the presence of the same chromophore and a variable number (1-4) of deprotected hexose units, has been prepared by employing succinate bridges for connecting the azo dye and the sugar portions. The modulation of the hydrophilic portion determines the appreciable changes in the water solubility of GADs. In all the cases, however, hydrophobic fibres (polyester) were homogeneously dyed with GADs at temperatures lower than that used for original azo dyes, at atmospheric pressure, and avoiding the use of surfactants. Furthermore, GADs show an interesting multipurpose character leading to dyeing well also the natural fibres as, for instance, wool. The presence of a variable number of hexose units in the different GADs determines some changes in the colour intensity of dyed fabrics, but in all the cases an appreciable rubbing and water fastness were maintained.     

Decolourization of azo dyes and a dye industry effluent by a white rot fungus Thelephora sp

A white rot fungus Thelephora sp. was used for decolourization of azo dyes such as orange G (50 microM), congo red (50 microM), and amido black 10B (25 microM). Decolourization using the fungus was 33.3%, 97.1% and 98.8% for orange G, congo red and amido black 10B, respectively. An enzymatic dye decolourization study showed that a maximum of 19% orange G was removed by laccase at 15 U/ml whereas lignin peroxidase (LiP) and manganese dependent peroxidase (MnP) at the same concentration decolourized 13.5% and 10.8%, orange G, respectively. A maximum decolourization of 12.0% and 15.0% for congo red and amido black 10B, respectively, was recorded by laccase. A dye industry effluent was treated by the fungus in batch and continuous modes. A maximum decolourization of 61% was achieved on the third day in the batch mode and a maximum decolourization of 50% was obtained by the seventh day in the continuous mode. These results suggest that the batch mode of treatment using Thelephora sp. may be more effective than the continuous mode for colour removal from dye industry effluents.     

Biodegradation of azo and anthraquinone dyes in continuous systems

The purpose is to develop a complete microbiological model system for the treatment of wastewater from textile mills in developing countries. Artificial wastewater was treated by microorganisms growing on wood shavings from Norway spruce during unsterile conditions. The microorganisms were inoculated from forest residues. Mixtures of the azo dyes Reactive Black 5 and Reactive Red 2 were degraded in batch as well as continuous experiments. Reactive Red 2 mixed with the anthraquinone dye Reactive Blue 4 was also treated in the continuous system. The system consisted of three reservoirs - the first two with an anaerobic environment and the third with an aerobic. The dye concentrations were 200 mg l⁻¹ of each dye in the continuous system and the retention time was approximately 4 days and 20 h per reservoir. Samples from the process were analysed with spectrophotometer and LC/MS to monitor the degradation process. 86-90% of the colour was removed after a treatment of 4 days and 23 h in the continuous process. Two metabolites were found in the outlets of reactors one and two, but they were degraded to below the detection limit in the aerobic reactor.     

Grifola frondosa extract and ergosterol reduce allergic reactions in an allergy mouse model by suppressing the degranulation of mast cells

ABSTRACT

The increasing number of patients suffering from allergic diseases is a global health problem. Grifola frondosa is an edible mushroom consumed as a health food in Asia, and has recently been reported to have anti-allergic effects. We previously reported that G. frondosa extract (GFE) and its active components, ergosterol and its derivatives, inhibited the antigen-induced activation of RBL-2H3 cells. Here, we demonstrated that GFE and ergosterol also had an inhibitory effect on the degranulation of bone marrow–derived mast cells (BMMCs) and alleviated anaphylactic cutaneous responses in mice. Using an air pouch-type allergic inflammation mouse model, we confirmed that oral administration of GFE and ergosterol suppressed the degranulation of mast cells in vivo. Our findings suggest that G. frondosa, including ergosterol as its active component, reduces type I allergic reactions by suppressing mast cell degranulation in mice, and might be a novel functional food that prevents allergic diseases.     

Reduction of azo dyes by anaerobic bacteria: microbiological and biochemical aspects

Azo dyes are recalcitrant pollutants commonly found in several industrial wastewaters, such as those originated from textile factories, which generally persist to biological transformation. Discharge of these effluents in open water bodies not only represents an aesthetic problem, but also may limit photosynthesis in aquatic plants. Furthermore, many azo dyes and products derived from their partial transformation in the environment (e.g. aromatic amines) may be toxic or carcinogenic. Biological wastewater treatment processes have emerged as promising technologies to remove azo dyes from industrial effluents and intensive research has been conducted during the last two decades in order to elucidate the mechanisms involved in the reductive decolourisation of azo dyes. The present work describes the main biochemical and microbiological aspects involved in the reductive decolourisation of azo dyes by anaerobic bacteria.     

Basic and applied aspects in the microbial degradation of azo dyes

Azo dyes are the most important group of synthetic colorants. They are generally considered as xenobiotic compounds that are very recalcitrant against biodegradative processes. Nevertheless, during the last few years it has been demonstrated that several microorganisms are able, under certain environmental conditions, to transform azo dyes to non-colored products or even to completely mineralize them. Thus, various lignolytic fungi were shown to decolorize azo dyes using ligninases, manganese peroxidases or laccases. For some model dyes, the degradative pathways have been investigated and a true mineralization to carbon dioxide has been shown. The bacterial metabolism of azo dyes is initiated in most cases by a reductive cleavage of the azo bond, which results in the formation of (usually colorless) amines. These reductive processes have been described for some aerobic bacteria, which can grow with (rather simple) azo compounds. These specifically adapted microorganisms synthesize true azoreductases, which reductively cleave the azo group in the presence of molecular oxygen. Much more common is the reductive cleavage of azo dyes under anaerobic conditions. These reactions usually occur with rather low specific activities but are extremely unspecific with regard to the organisms involved and the dyes converted. In these unspecific anaerobic processes, low-molecular weight redox mediators (e.g. flavins or quinones) which are enzymatically reduced by the cells (or chemically by bulk reductants in the environment) are very often involved. These reduced mediator compounds reduce the azo group in a purely chemical reaction. The (sulfonated) amines that are formed in the course of these reactions may be degraded aerobically. Therefore, several (laboratory-scale) continuous anaerobic/aerobic processes for the treatment of wastewaters containing azo dyes have recently been described.     

Fluorescent cytochemistry of acid phosphatase and demonstration of fluid-phase endocytosis using an azo dye method

 The aim of this work was the development of a fluorescent microscopy technique to visualize acid phosphatase activity in living and pre-fixed cells. We have shown that a coupling azo dye method, using naphthol AS-MX phosphate (NP) as substrate and fast red TR (FR) as a diazonium salt coupling agent, gives rise to a fluorescent azo dye reaction product which permits a highly sensitive demonstration of lysosomal acid phosphatase in both living and pre-fixed monolayer cell cultures. The granular staining is prevented by inhibition of acid phosphatase activity using fluoride and/or orthovanadate in both living and pre-fixed preparations. Lysosomal staining in living cells is also abolished by inhibition of fluid-phase endocytosis using low temperatures or inhibition of oxidative phosphorylation. It was shown that whilst NP entered living cells by passive diffusion, occurrence of FR in lysosomes resulted from fluid-phase endocytosis. Spectroscopic analysis of the emission and absorption features of FR, NP, naphthol AS-MX (N), and the N–FR azo dye reaction product in solution corroborated our microscopic results. The differing uptake mechanisms, and the occurrence of lysosomally localized azo dye, were also in keeping with the predictions of quantitative structure–activity relationship models of this system. Accepted: 24 April 1997     

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).     

Induced optical activity in the complex of poly(L-arginine) with azo dyes

The absorption and CD spectra of the complexes of poly(L -arginine) (PLA) and azo dyes have been measured in aqueous solution. On complexation, Blue-shifted additional absorption bands were observed. In the wide pH 4–11 range, induced CD was observed at the visible wavelengths corresponding to the blue-shifted absorption bands. The induced CD arose from the dimeric dye molecules bound to PLA in the α-helical structure. When a modified analysis of induced CE is made by the excition chirality method, the origin of the induced CD can be assigned to the dipole coupling. The PLA–dye complexes showed the counterlockwise (negative, S) chirality of the transition dipole moments of dyes.     

Fusarium oxysporum degradation and detoxification of a new textile-glycoconjugate azo dye (GAD)

Degradation and detoxification of textile dyes are of interest due to the huge environmental impact of such chemicals. An isolate of Fusarium oxysporum was used to degrade and to detoxify a new chemical class of textile dyes called Glycoconjugate Azo Dye (GAD). After 6 d of growth in a liquid batch culture, the fungus degraded the dye and the culture medium at the end of incubation period showed a ?100% detoxification compared to the initial dye solution. Increasing the initial fungal inoculum, the dye was totally decolourized after 24 h of incubation. The degradation ability was found to be common among various isolates of F. oxysporum suggesting this as a specific trait of this species. Degrading rate was enhanced in concomitancy to the glucose depletion and the beginning of the stationary phase of growth, suggesting that the shift from the primary to the secondary metabolism may be the trigger of the degradation pathway. The Daphnia magna acute toxicity test demonstrated a strong detoxification of GAD-4 by F. oxysporum, resulting in non-toxic metabolite production. Fusarium oxysporum could, therefore, be taken into consideration to develop new remediation strategies of textile effluents.     

The significance of azo-reduction in the mutagenesis and carcinogenesis of azo dyes

Azo dyes are widely used in textile, printing, cosmetic, drug and food-processing industries. They are also used extensively in laboratories as either biological stains or pH indicators. The extent of such use is related to the degree of industrialization. Since intestinal cancer is more common in highly industrialized countries, a possible connection may exist between the increase in the number of cancer cases and the use of azo dyes. Azo dyes can be reduced to aromatic amines by the intestinal microflora. The mutagenicity of a number of azo dyes is reviewed in this paper. They include Trypan Blue, Ponceau 3R, Pinceau 2R, Methyl Red, Methyl Yellow, Methyl Orange, Lithol Red, Orange I, Orange II, 4-Phenylazo-Naphthylamine, Sudan I, Sudan IV, Acid Alizarin Violet N, Fast Garnet GBC, Allura Red, Ponceau SX, Sunset Yellow, Tartrazine, Citrus Red No. 2, Orange B, Yellow AB, Carmoisine, Mercury Orange, Ponceau S, Versatint Blue, Phenylazophenol, Evan's Blue and their degraded aromatic amines. The significance of azo reduction in the mutagenesis and carcinogenesis of azo dyes is discussed.     

Mutagenicity of anthraquinone and azo dyes in Ames' Salmonella typhimurium test.

23 dyes belonging to different chemical classes--anthraquinones, mono- and bis-azo compounds--were tested for their mutagenic activity on Ames strains of Salmonella typhimurium. 5 dyes induced frameshift mutations.     

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.