Effluent-contaminated Soil Research Articles

Biofabrication, spectroscopic, and photocatalytic studies of titania nanoparticles mediated by Proteus mirabilis strain NG-ABK-32 for smart applications

ABSTRACT Green fabrication of nanoparticles (NPs) is simple, pocket-friendly, easy, sustainable, and devoid of eco-toxicity issues. Thirty-five bacterial strains were isolated from ‘tie and dye’ effluent-contaminated soil and effluent samples and were identified using traditional methods. Following a dye decolourization assay, Proteus mirabilis strain (NG-ABK-32) emerged as the isolate with the highest potential to decolourize vat violet RR dye. Titania nanoparticles (TiO2 NPs) fabricated using NG-ABK-32 strain were characterized by UV-visible spectroscopy (UV-vis), Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD), and Fourier Transform Infrared (FT-IR) spectroscopy. UV-Vis result displayed an absorption peak at 320 nm. The TEM image revealed monodispersed, spherical NPs possessing an average particle size of 3.18 nm. The crystallographic plane of rutile TiO2 NPs and high purity were confirmed by the XRD pattern. The average crystallite size was 52.53 nm. The synthesis of TiO2 NPs was further established from FT-IR by the presence of Ti-O, Ti-OH, and O-Ti-O functional groups. The synergistic treatment caused a significant reduction of total suspended solids (TSS), total dissolved solids (TDS), biological oxygen demand (BOD), chemical oxygen demand (COD), and color (Pt.Co) of the effluent by 96.86%, 78.78%, 67.84%, 56.65%, 67.84%, and 72.09% respectively. Thus, this study confirmed the better efficiency of combining biological (NG-ABK-32) pre-treatment with photocatalytic degradation post-treatment using the synthesized TiO2 NPs in the treatment of ‘tie and dye’ effluent compared to the application of the TiO2 NPs as a single treatment method.

Bacterial Diversity and Occurrences in Cassava Effluent-Contaminated Soil Collected From Ozubulu, Anambra State, Nigeria

Environmental degradation due to indiscriminate disposal of refuse has a tremendous effect on microbial activities in the soil. Most soil in Nigeria has been subjected to different kinds of pollutants resulting from anthropogenic activities which have become a major threatening factor to the quality of soil. This study was undertaken to evaluate bacterial diversity and occurrences in cassava effluent contaminated soil from Ozubulu, Anambra State. A total of 30 composite soil samples were aseptically collected from cassava effluent disposal site using a sterile soil auger. The predominant bacterial isolates that aided nutrients cycling were appropriately characterized, and their diversities in both impacted and non-impacted soil samples were enumerated. Furthermore, the bacterial isolates were characterized based on morphology, microscopy, and biochemical characteristics. There was a significant reduction in the occurrences of the bacterial isolates in the impacted soil, and Gram negative rods such as Pseudomonas, Klebsiella and Micrococcus (Gram positive) species were the bacterial isolates. The study has revealed that cassava effluent affects microbial distribution in the soil. Keywords: Bacterial, Diversity, Occurrences, Cassava, Effluent-Contaminated and Soil

Degradation of tannery hide raw trimming hairs using keratinolytic bacteria isolated from tannery effluent-contaminated soil.

The disposal of keratinous wastes produced by several leather industries is evolving into a global problem. Around 1 billion tonnes of keratin waste are released into the environment each year. In the breakdown of tannery waste, certain enzymes, such as keratinases produced from microorganisms, might be a better substitute for synthetic enzymes. Keratinase enzymes are able to hydrolyze gelatin, casein, bovine serum albumin and insoluble protein present in wool, feather. Therefore, in this study, bacterial strains from tannery effluent-contaminated soil and bovine tannery hidewere isolated and assessed for their ability to produce the keratinolytic enzyme. Among the six isolates, the strain NS1P showed the highest keratinase activity (298 U/ml) and was identified as Comamonas testosterone through biochemical and molecular characterization. Several bioprocess parameters such as pH, temperature, inoculum size, carbon sources, and nitrogen sources were optimized in order to maximize crude enzyme production. The optimized media were used for inoculum preparation and subsequent biodegradation of hide hairs. The degradation efficacy of the keratinase enzyme produced by Comamonas testosterone was examined by degrading bovine tanneryhide hairs, and it was found to be 73.6% after 30days. The morphology of the deteriorated hair was examined using a field emission scanning electron microscope (FE-SEM), which revealed significant degradation. Thus, our research work has led to the conclusion that Comamonas testosterone may be a promising keratinolytic strain for the biodegradation of tannery bovine hide hair waste and the industrial production of keratinases.

Bioprospecting uncultivable microbial diversity in tannery effluent contaminated soil using shotgun sequencing and bio-reduction of chromium by indigenous chromate reductase genes

The tannery industry generates a consequential threat to the environment by producing a large amount of potentially toxic metal-containing waste. Bioremediation has been a promising approach for treating potentially toxic metals, but the efficiency of remediation in microbes is one of the factors limiting their application in tanneries waste treatment. The motivation behind the present work was to explore the microbial diversity and chromate reductase genes present in the tannery effluent-contaminated soil using metagenomics approach. The use of shotgun sequencing enabled the identification of operational parameters that influence microbiome composition and their ability to reduce Chromium (Cr) concentration. The Cr concentration in Kanpur tannery effluent contaminated soil sample was 700 ppm which is many folds than the approved permissible limit by World Health Organisation (WHO) for Cr is 100 ppm. Metagenomic Deoxyribo Nucleic Acid (DNA) was extracted to explore taxonomic community structure, phylogenetic linkages, and functional profile. With a Guanine-Cytosine (GC) abundance of 54%, total of 45,163,604 high-quality filtered reads were obtained. Bacteria (83%), Archaebacteria (14%), and Viruses (3%) were discovered in the structural biodiversity. Bacteria were classified to phylum level, with Proteobacteria (52%) being the dominant population, followed by Bacteriodetes (15%), Chloroflexi (15%), Spirochaetes (7%), Thermotogae (5%), Actinobacteria (4%), and Firmicutes (1%). The OXR genes were cloned and checked for their efficiency to reduce Cr concentration. Insitu validation of OXR8 gene showed a reduction of Cr concentration from 700 ppm to 24 ppm in 72 h (96.51% reduction). The results of this study suggests that there is a huge reservoir of microbes and chromate reductase genes which are unexplored yet.

Fungal biosorption of the heavy metals chromium(VI) and nickel from industrial effluent-contaminated soil

Heavy metals are ubiquitous contaminants that have accompanied man since the earliest ancient times, and unlike other environmental pollutants, they are chemical elements that man does not create or destroy. In the present study, the aim was to determine the biosorption potential of heavy metal-tolerant fungi that were isolated from compost soil samples contaminated by industrial effluents. The isolation was performed on potato dextrose agar (PDA) media supplemented with heavy metals. Chromium-Cr(VI) and nickel-Ni. The most dominant fungal species were found to be Penicillium spp. This fungus was screened for its ability to tolerate heavy metals by the plate diffusion and broth method and was highly tolerant to fungal species. The fungi were assessed for their ability to remove heavy metals from the culture media, and the culture conditions for the fungus were experimentally optimized. The isolated Penicillium species was found to show maximum growth at 35°C with media pH 6 for an incubation period of 168 hours. The isolate was able to tolerate 60-70 ppm concentrations of heavy metals under normal conditions. The ability of the isolate to take up metal was very effective, as after 96 hrs of incubation, it was capable of removing approximately 93.8% of Cr(VI) and 95.6% of Ni from the culture media, and complete uptake was observed after a 144 hr incubation period. The molecular characterization revealed the only isolate to be Penicillium rubens (Accession no. LC536286). The morphological characteristics of this fungus make it capable of biosorption of heavy metals, imparting its bioremediation potential and economic importance.

Structural Characterisation and Assessment of the Novel Bacillus amyloliquefaciens RK3 Exopolysaccharide on the Improvement of Cognitive Function in Alzheimer's Disease Mice.

In this study Bacillus amyloliquefaciens RK3 was isolated from a sugar mill effluent-contaminated soil and utilised to generate a potential polysaccharide with anti-Alzheimer’s activity. Traditional and molecular methods were used to validate the strain. The polysaccharide produced by B. amyloliquefaciens RK3 was purified, and the yield was estimated to be 10.35 gL−1. Following purification, the polysaccharide was structurally and chemically analysed. The structural analysis revealed the polysaccharide consists of α-d-mannopyranose (α-d-Manp) and β-d-galactopyranose (β-d-Galp) monosaccharide units connected through glycosidic linkages (i.e., β-d-Galp(1→6)β-d-Galp (1→6)β-d-Galp(1→2)β-d-Galp(1→2)[β-d-Galp(1→6)]β-d-Galp(1→2)α-d-Manp(1→6)α-d-Manp (1→6)α-d-Manp(1→6)α-d-Manp(1→6)α-d-Manp). The scanning electron microscopy and energy-dispersive X-ray spectroscopy imaging of polysaccharides emphasise their compactness and branching in the usual tubular heteropolysaccharide structure. The purified exopolysaccharide significantly impacted the plaques formed by the amyloid proteins during Alzheimer’s disease. Further, the results also highlighted the potential applicability of exopolysaccharide in various industrial and pharmaceutical applications.

ROCK PHOSPHATE SOLUBILIZATION AND ENZYMATIC ACTIVITIES FROM INDIGENOUS BACTERIA ON CASSAVA MILL EFFLUENT CONTAMINATED SOIL

The processing of cassava into value-added products is associated with discharge of effluents which contain substances that have adverse effect on the environment. Remediative activity of indigenous bacteria can be stimulated by supplementing effluents with phosphorus. Rock phosphate (RP) solubilization and enzymatic activities from bacteria on the cassava mill effluents (CME) contaminated soil was investigated. Soil mixed with varying concentrations of CME (0, 100, 200, 300, 400, 500 and 600 ml) and 10 g of RP were analyzed on days 0 and 16. Parameters analyzed were changes in pH, heterotrophic bacteria load, phosphate-solubilizing bacteria load, available phosphorus, acid phosphatase, cellulase and urease concentrations. The results showed that the medium containing 400 ml CME contaminated soil had the highest phosphate-solubilizing bacteria load (12.60 ± 2.08 x 106 cfu/ml), available phosphorus (126.00 ± 4.08 mg/kg), acid phosphatase (9.54 ± 0.51 mgN/g/min), cellulase (15.24 ± 0.81 mg/g/6h) and urease concentration (2.15±0.22 mg/g/2h). The control had the lowest phosphate-solubilizing bacteria load and enzymatic activity. Biostimulation of indigenous bacteria to enhance the degradation of cassava mill effluent-contaminated soil, using rock phosphate, showed promising results. This implies that rock phosphate solubilization by indigenous bacteria in CME-contaminated soils could be important for the remediation and reclamation of contaminated lands.

Phytoremediation of Lead and Chromium Contaminated Soil Improves with the Endogenous Phenolics and Proline Production in Parthenium, Cannabis, Euphorbia, and Rumex Species

Phytoremediation is the most promising and emerging technology for remediation of metal-contaminated sites. The aim of the current research was to investigate the metals accumulation potential of four weed species i.e., Parthenium, Cannabis, Euphorbia, and Rumex species. The endogenous free proline, total phenolic, carotenoids, and chlorophyll contents were assessed under metals stress and correlated with metals accumulation in plants. Plants of each species were allowed to grow in reference (uncontaminated) soil and other group on industrial effluent-contaminated soil under natural environment. Phytoextraction potentials of these plants were evaluated for removal of lead (Pb) and chromium (Cr). The heavy metal concentration in plant parts was analyzed by atomic absorption spectrophotometer. Varied accumulation of metals was found among different weed species. Moreover, metal accumulation was different within plant tissues i.e., roots, leaves, and stem. Cannabis and Parthenium showed bio-concentration BCF > 1 for Pb, reflecting their high metal accumulation potential and both plants were found superior than Rumex and Euphorbia for Cr accumulation. The endogenous free proline and phenolic contents showed significantly positive correlation with Pb accumulation in four plants i.e., Parthenium (R2 = 0.977, R2 = 0.9996), Cannabis (R2 = 0.9924, R2 = 0.9999), Euporbia (R2 = 0.9992, R2 = 0.9832), Rumex (R2 = 0.6033, R2 = 0.8272) respectively. Similarly, Cr accumulation in plants showed significantly positive correlation with proline and phenolic but the BCF ˂ 1.The chlorophyll and carotenoids contents in all plants negatively correlated with Pb and Cr concentration.

Carbon and Nitrogen Sources for Lipase Production of Micrococcus sp. Isolated from Palm Oil Mill Effluent-Contaminated Soil

This research aim to optimize the lipase production of Micrococcus sp. isolated from oil palm contaminated soil. The production of lipase enzymes is carried out in modified medium containing olive oil, sea salt, yeast extract with various types of carbon source (glucose, sucrose, glycerol) and nitrogen sources (tryptone, ammonium phosphate, urea and ammonium nitrate). The activity of lipase enzyme was determined by UV-Vis spectrophotometry method toward ρ-nitrophenylpalmitate (ρ-NPP) as a substrate. The results showed that glucose 1% was better carbon source compared with sucrose and glycerol. Ammonium phosphate, urea and ammonium nitrate were good nitrogen sources for lipase production of Micrococcus sp., although tryptone was the best nitrogen source.

Tracking effluent discharges in undisturbed stony soil and alluvial gravel aquifer using synthetic DNA tracers

With the intensification of human activities, fresh water resources are increasingly being exposed to contamination from effluent disposal to land. Thus, there is a greater need to identify the sources and pathways of water contamination to enable the development of better mitigation strategies. To track discharges of domestic effluent into soil and groundwater, 10 synthetic double-stranded DNA (dsDNA)33Double-stranded DNA (dsDNA); single-stranded DNA (ssDNA); base-pair (bp); bromide (Br); polymerase chain reaction (PCR); colony-forming units (cfu); relative mass recovery (RB); relative transport speed (RV); relative dispersion (RS); concentration breakthrough curve (BTC). tracers were developed in this study. Laboratory column experiment and field groundwater and soil lysimeter studies were carried out spiking DNA with oxidation-pond domestic effluent. The selected DNA tracers were compared with a non-reactive bromide (Br) tracer with respect to their relative mass recoveries, speeds of travel and dispersions using the method of temporal moments. In intact stony soil and gravel aquifer media, the dsDNA tracers typically showed earlier breakthrough and less dispersion than the Br tracer, and underwent mass reduction. This suggests that the dsDNA tracers were predominantly transported through the network of larger pores or preferential flow paths. Effluent tracking experiments in soil and groundwater demonstrated that the dsDNA tracers were readily detectable in effluent-contaminated soil and groundwater using quantitative polymerase chain reaction. DNA tracer spiked in the effluent at quantities of 36μg was detected in groundwater 37m down-gradient at a concentration 3-orders of magnitude above the detection limit. It is anticipated it could be detected at far greater distances. Our findings suggest that synthetic dsDNA tracers are promising for tracking effluent discharges in soils and groundwater but further studies are needed to investigate DNA-effluent interaction and the impact of subsurface environmental conditions on DNA attenuation. With further validation, synthetic dsDNA tracers, especially when multiple DNA tracers are used concurrently, can be an effective new tool to track effluent discharge in soils and groundwater, providing spatial estimation on the presence or absence of contamination sources and pathways.

Removal of Cr (VI) from tannery effluents with mixed cultures of bacteria and fungi isolated from soils contaminated with tropical tannery effluents

Pseudomonas aeruginosa, Escherichia coli, Aspergilllus niger and Penicillium chrysogenum isolated from tannery effluent-contaminated soil showed resistance to chromium [Cr (VI)] with minimum inhibitory concentrations (MIC) of 80-120 mg/l in potato dextrose or nutrient agar. This increased to 100-150 mg/l in glucose and yeast extract supplemented mineral salts medium. Significant removal of Cr (VI) occurred in tannery effluents treated with the isolates singly, although reductions were >0.05 mg/l (stipulated limit) in all treatments. Chromium was reduced in glucose, beef and yeast extracts supplemented effluents to non-detectable levels < 0.05 mg/l in all except in E. coli treatment. However, mixed cultures' treatment of non-supplemented effluent reduced Cr (V1) below 0.05 mg/l with the consortium of P. aeruginosa, P. chysogenum and A. niger reaching 99.6-100% removal. Mixed bacterial and fungal culture may be of potential cost effective application in the removal of chromium in tannery wastes.

Purification and characterization of a highly active chromate reductase from endophytic Bacillus sp. DGV19 of Albizzia lebbeck (L.) Benth. actively involved in phytoremediation of tannery effluent-contaminated sites

ABSTRACTPhytoremediation using timber-yielding tree species is considered to be the most efficient method for chromium/tannery effluent-contaminated sites. In this study, we have chosen Albizzia lebbeck, a chromium hyperaccumulator plant, and studied one of its chromium detoxification processes operated by its endophytic bacterial assemblage. Out of the four different groups of endophytic bacteria comprising Pseudomonas, Rhizobium, Bacillus, and Salinicoccus identified from A. lebbeck employed in phytoremediation of tannery effluent-contaminated soil, Bacillus predominated with three species, which exhibited not only remarkable chromium accumulation ability but also high chromium reductase activity. A chromate reductase was purified to homogeneity from the most efficient chromium accumulator, Bacillus sp. DGV 019, and the purified 34.2-kD enzyme was observed to be stable at temperatures from 20°C to 60°C. The enzyme was active over a wide range of pH values (4.0–9.0). Furthermore, the enzyme activity was enhanced with the electron donors NADH, followed by NADPH, not affected by glutathione and ascorbic acid. Cu2+ enhanced the activity of the purified enzyme but was inhibited by Zn2+ and etheylenediamine tetraacetic acid (EDTA). In conclusion, due to its versatile adaptability the chromate reductase can be used for chromium remediation.

Phytoremediation potential of chromium-containing tannery effluent-contaminated soil by native Indian timber-yielding tree species

ABSTRACTTwenty-six native Indian tree species that are used for the enhanced tree cover program of the forest department (Government of Tamilnadu, India) were screened for phytoremediation of tannery effluent-contaminated soil containing high chromium content. Out of 26 tree species tested, 10 timber-yielding tree species were selected for further phytoremediation monitoring. After a series of treatments with tannery effluent sludge, the chromium content was measured in the plant parts. The saplings of Acacia auriculiformis, Azadirachta indica, Albizzia lebbeck, Dalbergia sisso, and Thespesia populnea were identified as efficient bioaccumulators of chromium from Cr-contaminated soil. Acacia auriculiformis accumulates higher amounts of Cr in both the root and stem. Dalbergia sisso and T. populnea were found to accumulate higher quantity of Cr in the roots, whereas A. indica, A. richardiana, and A. lebbeck accumulate Cr in their stem. The stress response of the plant species was assessed by quantifying the antioxidative enzymes such as catalase, superoxide dismutase, glutathione reductase, and DHAR. Activity of all the enzymes was observed to gradually increase following treatment with tannery effluent sludge.

Chromium phytoextraction from tannery effluent-contaminated soil by Crotalaria juncea infested with Pseudomonas fluorescens

The aim of present study was to remediate chromium (Cr)-contaminated soil by Crotalaria juncea in the presence of Pseudomonas fluorescens. Inoculation of P. fluorescens in pot soil grown with C. juncea significantly increased (~2-fold) the water-soluble (Ws) and exchangeable (Ex) Cr contents in contaminated soil under greenhouse condition. It also enhanced the chlorophyll content by 92 % and plant biomass by 99 % as compared to the uninoculated C. juncea plant. The analysis showed that root and shoot uptake of Cr in C. juncea inoculated by P. fluorescens was 3.08- and 2.82-fold, respectively. This research showed that the association of C. juncea and P. fluorescens could be a promising technology for increasing the soil Cr bioavailability and plant growth for successful phytoextraction of Cr from the contaminated soil.

Isolation and characterization of phenol utilizing bacteria from industrial effluent-contaminated soil and kinetic evaluation of their biodegradation potential

Microbial degradation of phenol by pure bacterial species is a well-known approach towards alleviation of environmental pollution. In this study, five phenol-degrading bacterial species designated as CUPS-1 to CUPS-5 were isolated from the oil-effluent dumped sites of Haldia Industrial area of West Bengal, India. Detailed morphological, biochemical and molecular characterization identified CUPS-3 as a novel strain- Stenotrophomonas maltophilia (GU358076), while the others could be identified as Pseudomonas (CUPS-2, 5), Delftia (CUPS-1) and Micrococcus (CUPS-4) genera, respectively. Although all of these strains utilized phenol as their sole carbon source supporting growth, three among them, CUPS-2, CUPS-3 and CUPS-5 proved potential phenol degraders and hence used for further biodegradation studies. Degradation experiments were carried out for several initial phenol concentrations of 500 mg/L, 750 mg/L, 1000 mg/L, 1250 mg/L and 1500 mg/L. The novel strain, CUPS-3 could completely degrade 500 mg/L phenol within 48 h, with 0.0937/h substrate degradation rate and 16.34 mg/L/h substrate consumption rate. The strains degraded phenol via meta-cleavage pathway. Prediction of kinetic parameters of the biodegradation was accomplished Haldane model using the experimental data of degradation rate and phenol concentration as function of time.

Mechanistic investigation of decolorization and degradation of Reactive Red 120 by Bacillus lentus BI377

Bacillus lentus BI377, isolated from textile effluent-contaminated soil, was able to degrade 97% and 92% of Reactive Red 120 dye when 1200 and 1500 mg/l, respectively, of dye was added to nutrient broth (NB) at 35 °C within 12 h. UV-vis spectroscopy, GC-MS, FTIR and 1H NMR revealed the formation of catechol which may be further utilized by the bacterium via the TCA cycle, leading to complete mineralization. Structural analysis of metabolites in conjunction with enzyme activity studies confirmed the involvement of azoreductase, cytochrome P450 monooxygenase and other antioxidant enzymes. Decreases in total organic carbon and in biological and chemical oxygen demand suggest formation of low molecular weight metabolites that could be completely mineralized. These results suggest the potential use of B. lentus BI377 towards online treatment of textile dye effluents by using an appropriate bioreactor over a wide range of pH. This study opens-up a dependable and proficient way to use industrially viable non-pathogenic strains for biotransformation of carcinogenic dyes to ecofriendly compounds.

Effect of Pseudomonas fluorescens on metal phytoextraction from contaminated soil by Brassica juncea

The present study deals with metal uptake by Brassica juncea in the presence of Pseudomonas fluorescens Pf 27 for Zn, Cu and Cd removal from brass and electroplating-industry effluent-contaminated soil. Inoculation of P. fluorescens significantly (p<0.05) increased water soluble (Ws) and exchangeable (Ex) metal content in contaminated soil in laboratory conditions and also enhanced plant biomass by 99% and chlorophyll content by 91% as compared to uninoculated plants in the greenhouse. The metal uptake by B. juncea followed the pattern Zn>Cu>Cd and increased with increasing plant growth duration. P. fluorescens inoculation increased root and shoot uptake of Zn by 3.05 and 2.69, Cu by 3.19 and 2.82 and Cd by 3.11- and 2.75-fold, respectively. BCF value for each metal was>1 and increased by 44%, 42% and 38% for Zn, Cu and Cd, respectively, in inoculated conditions, whereas TF remained unaffected and followed the order Zn>Cd>Cu. P. fluorescens inoculation also enhanced Ws fraction of Zn, Cu and Cd by 99%, 77% and 90% and Ex by 107%, 70% and 93%, respectively. Results depicted that association of B. juncea with P. fluorescens could be a promising strategy for enhancing soil metal bioavailability and plant growth for successful phytoremediation of heavy metal contaminated soils.

Microbial decolorization of reactive azo dyes in a sequential anaerobic–aerobic system

A sequential anaerobic–aerobic treatment process based on mixed culture of bacteria isolated from textile dye effluent-contaminated soil was used to degrade reactive azo dyes Remazol Brilliant Orange 3R. Remazol Black B and Remazol Brilliant Violet 5R. Treating synthetic dye wastewater with the combination anaerobic and aerobic process showed that the majority of colors were removed by the anaerobic process, on the other hand the majority of chemical oxygen demand (COD) was removed in the subsequent aerobic process. Samples from combined anaerobic–aerobic system at the beginning of anaerobic process, after anaerobic process and after subsequent aerobic process were analyzed by high performance liquid chromatography (HPLC). The results suggested that under anaerobic conditions, the azo dyes were reduced and the aromatic amines were generated by the bacterial biomass. After re-aeration of the synthetic dye wastewater, these amines were further degraded by the same isolates. Thus, total degradation of reactive azo dyes was achieved by using an anaerobic–aerobic treatment.

Biodegradation of azo dyes in a sequential anaerobic-aerobic system.

A sequential anaerobic aerobic treatment process based on mixed culture of bacteria isolated from textile dye effluent-contaminated soil was used to degrade sulfonated azo dyes Orange G (OG), Amido black 10B (AB), Direct red 4BS (DR) and Congo red (CR). Under anaerobic conditions in a fixed-bed column using glucose as co-substrate, the azo dyes were reduced and amines were released by the bacterial biomass. The amines were completely mineralized in a subsequent aerobic treatment using the same isolates. The maximum degradation rate observed in the treatment system for OG was 60.9 mg/l per day (16.99 mg/g glucose utilized), for AB 571.3 mg/l per day (14.46 mg/g glucose utilized), for DR 112.5 mg/l per day (32.02 mg/g glucose utilized) and for CR 134.9 mg/l per day (38.9 mg/g glucose utilized).