Organ-distribution of the metabolite 2-aminothiazoline-4-carboxylic acid in a rat model following cyanide exposure

The reaction of cyanide (CN^?) with cystine to produce 2-aminothiazoline-4-carboxylic acid (ATCA) is one of the independent detoxification pathways of cyanide in biological systems. In this report, in vivo production of ATCA and its distributions in plasma and organs were studied after a subcutaneous sublethal dose of 4?mg/kg body weight potassium cyanide (KCN) administration to rats. At this sublethal dose of KCN, ATCA concentration was not significantly increased in the plasma samples, however, it was found significantly increased in liver samples. These results suggested that ATCA might not be a good diagnostic biomarker in plasma for sublethal cyanide exposure; however, liver could serve as the right organ for the detection of ATCA in post-mortem examinations involving cyanide exposure in military, firefighting, industrial and forensic settings.     

Treatment of cyanide-containing wastewater from the food industry in a laboratory-scale fixed-bed methanogenic reactor

During the process of producing cassava starch from Manihot esculenta roots, large amounts of cyanoglycosides were released, which rapidly decayed to CN⁻ following enzymatic hydrolysis. Depending on the varying cyanoglycoside content of the cassava varieties, the cyanide concentration in the wastewater was as high as 200 mg/l. To simulate anaerobic stabilization, a wastewater with a chemical oxygen demand (COD) of about 20 g/l was prepared from cassava roots and was fermented in a fixed-bed methanogenic reactor. The start-up phase for a 99% degradation of low concentrations of cyanide (10 mg/l) required about 6 months. After establishment of the biofilm, a cyanide concentration of up to 150 mg CN⁻/l in the fresh wastewater was degraded during anaerobic treatment at a hydraulic retention time of 3 days. All nitrogen from the degraded cyanide was converted to organic nitrogen by the biomass of the effluent. The cyanide-degrading biocoenosis of the anaerobic reactor could tolerate shock concentrations of cyanide up to 240 mg CN⁻/l for a short time. Up to 5 mmol/l NH₄Cl (i.e. 70 mg N/l = 265 mg NH₄Cl/l) in the fresh wastewater did not affect cyanide degradation. The bleaching agent sulphite, however, had a negative effect on COD and cyanide removal. For anaerobic treatment, the maximum COD space loading was 12 g l⁻¹ day⁻¹, equivalent to a hydraulic retention time of 1.8 days. The COD removal efficiency was around 90%. The maximum permanent cyanide space loading was 50 mg CN⁻ l⁻¹ day⁻¹, with tolerable shock loadings up to 75 mg CN⁻ l⁻¹day⁻¹. Under steady-state conditions, the cyanide concentration of the effluent was lower than 0.5 mg/l. Received: 15 August 1997 / Received revision: 10 October 1997 / Accepted: 14 October 1997     

Molecular interaction of acrylonitrile and potassium cyanide with rat blood

The interaction of acrylonitrile (VCN) with rat blood has been investigated at the molecular level in an attempt to understand the possible mechanism of its toxicity. The results obtained were compared to those with potassium cyanide (KCN), a compound known to liberate cyanide (CN^?) in biologic conditions. The radioactivity derived from K¹⁴CN was eliminated faster than that from [1-¹⁴C]VCN. Up to a maximum of 94% of ¹⁴C from VCN in erythrocytes was detected covalently bound to cytoplasmic and membrane proteins, whereas 90% of the radioactivity from KCN in erythrocytes was found in the heme fraction of hemoglobin. Determination of specific activity showed that binding occurred more in vivo than in vitro which indicated that the VCN molecule was bioactivated inside erythrocytes. These results indicate that KCN interacts mainly through CN^? liberation and binding to heme, whereas VCN, which binds to cytoplasmic and membrane proteins, may cause damage to red cells by mechanisms other than release of CN^?.     

Mechanism of cyanide and thiocyanate decomposition by an association of Pseudomonas putida and Pseudomonas stutzeri strains

The intermediate and terminal products of cyanide and thiocyanate decomposition by individual strains of the genus Pseudomonas, P. putida strain 21 and P. stutzeri strain 18, and by their association were analyzed. The activity of the enzymes of nitrogen and sulfur metabolism in these strains was compared with that of the collection strains P. putida VKM B-2187^T and P. stutzeri VKM B-975^T. Upon the introduction of CN⁻ and SCN⁻ into cell suspensions of strains 18 and 21 in phosphate buffer (pH 8.8), the production of NH ₄ ⁺ was observed. Due to the high rate of their utilization, NH₃, NH ₄ ⁺ , and CNO⁻ were absent from the culture liquids of P. putida strain 21 and P. stutzeri strain 18 grown with CN⁻ or SCN⁻. Both Pseudomonas strains decomposed SCN⁻ via cyanate production. The cyanase activity was 0.75 μmol/(min mg protein) for P. putida strain 21 and 1.26 μmol/(min mg protein) for P. stutzeri strain 18. The cyanase activity was present in the cells grown with SCN⁻ but absent in cells grown with NH ₄ ⁺ . Strain 21 of P. putida was a more active CN⁻ decomposer than strain 18 of P. stutzeri. Ammonium and CO₂ were the terminal nitrogen and carbon products of CN⁻ and SCN⁻ decomposition. The terminal sulfur products of SCN⁻ decomposition by P. stutzeri strain 18 and P. putida strain 21 were thiosulfate and tetrathionate, respectively. The strains utilized the toxic compounds in the anabolism only, as sources of nitrogen (CN⁻ and SCN⁻) and sulfur (SCN⁻). The pathway of thiocyanate decomposition by the association of bacteria of the genus Pseudomonas is proposed based on the results obtained. Original Russian Text ? N.V. Grigor’eva, T.F. Kondrat’eva, E.N. Krasil’nikova, G.I. Karavaiko, 2006, published in Mikrobiologiya, 2006, Vol. 75, No. 3, pp. 320–328.     

Activity of a novel bactericide,zinc thiazole against Xanthomonas oryzae pv. oryzae in Anhui Province of China

Bacterial leaf blight of rice (BLB), caused by Xanthomonas oryzae pv oryzae, is one of the most serious bacterial diseases in China. Presently, bismerthiazol has been the major bactericide for the control of BLB, however, bismerthiazol‐resistant strains of X. oryzae pv. oryzae have appeared in the field in China. Zinc thiazole is a novel bactericide with strong antibacterial activity against Xanthomonas spp. In this study, sensitivity of 109 X. oryzae pv. oryzae strains to zinc thiazole was determined. The EC₅₀ values for zinc thiazole in inhibiting bacterial growth of the 109 X. oryzae pv. oryzae strains were 0.53–9.62 µg mL^?1 with the average EC₅₀ value of 4.82 ± 1.86 µg/ml. The minimum inhibitory concentration (MIC) values of zinc thiazole against the 109 X. oryzae pv. oryzae strains were assessed and the results showed that the MIC values of zinc thiazole for completely inhibiting the growth of these 109 strains ranged from 5.0 to 40.0 µg mL^?1. In the evaluation of protective and curative activity test, zinc thiazole exhibited great activity against BLB and provided over 88% control efficacy (at 300 µg mL^?1) 1 and 3 days before or after inoculations, which was also higher that that of bismerthiazol in the corresponding treatments. Our field trials showed that zinc thiazole at 375 g.a.i ha^?1 provided over 70% control efficacy in 2012 and over 80% control efficacy in 2013 at both sites. Moreover, in all the four field trials, zinc thiazole at 250 g.a.i ha^?1 provided higher control efficacy than that of bismerthiazol at 250 g.a.i ha^?1. Taken together, zinc thiazole is therefore an alternative tool for the management of BLB.     

Biosorption of iron(III)–cyanide complex anions to Rhizopus arrhizus: application of adsorption isotherms

The biosorption of iron(III)–cyanide complex anions to Rhizopus arrhizus was investigated. The iron(III)–cyanide complex ion binding capacity of the biosorbent was a function of initial pH, initial iron(III)–cyanide complex ion and biosorbent concentration. These results indicated that a significant reduction of iron(III)–cyanide complex ions was achieved at pH 13, a highly alkaline condition. The maximum loading capacity of biosorbent was 612·2 mg g⁻¹ at 1996·2 mg litre⁻¹ initial iron(III)–cyanide complex ion concentration at this pH. The Freundlich, Langmuir and Redlich–Peterson adsorption models were fitted to the equilibrium data at pH 3·0, 7·0 and 13·0. The equilibrium data could be best fitted to by all the adsorption models over the entire concentration range (50–2000 mg litre⁻¹) at pH 13.     

Interaction of dimeric horse cytochrome c with cyanide ion

We have previously shown that methionine–heme iron coordination is perturbed in domain-swapped dimeric horse cytochrome c. To gain insight into the effect of methionine dissociation in dimeric cytochrome c, we investigated its interaction with cyanide ion. We found that the Soret and Q bands of oxidized dimeric cytochrome c at 406.5 and 529 nm redshift to 413 and 536 nm, respectively, on addition of 1 mM cyanide ion. The binding constant of dimeric cytochrome c and cyanide ion was obtained as 2.5 × 10⁴ M^?1. The Fe–CN and C–N stretching (ν _Fe–CN and ν _CN) resonance Raman bands of CN^?-bound dimeric cytochrome c were observed at 443 and 2,126 cm^?1, respectively. The ν _Fe–CN frequency of dimeric cytochrome c was relatively low compared with that of other CN^?-bound heme proteins, and a relatively strong coupling between the Fe–C–N bending and porphyrin vibrations was observed in the 350–450-cm^?1 region. The low ν _Fe–CN frequency suggests weaker binding of the cyanide ion to dimeric cytochrome c compared with other heme proteins possessing a distal heme cavity. Although the secondary structure of dimeric cytochrome c did not change on addition of cyanide ion according to circular dichroism measurements, the dimer dissociation rate at 45 °C increased from (8.9 ± 0.7) × 10^?6 to (3.8 ± 0.2) × 10^?5 s^?1, with a decrease of about 2 °C in its dissociation temperature obtained with differential scanning calorimetry. The results show that diatomic ligands may bind to the heme iron of dimeric cytochrome c and affect its stability.     

Equilibrium and Kinetics of Adsorption of Mn2+ by Haloarchaeon Halobacterium sp. GUSF (MTCC3265)

The coastal waters of countries bordering on an ocean show increases in manganese pollution due to runoff from mining activity and from industries dealing with production of ferroalloys, steel, iron, petrochemicals, and fertilizers. One gram of dried cells of haloarchaeon Halobacterium sp. GUSF (MTCC3265) adsorbed 99% Mn²⁺ in 60 min at pH 6.8 and 30ºC on contact with 109.54 mg Mn²⁺ per liter in saline solution. Adsorbed Mn²⁺ was quantified by atomic absorption spectrometry and demonstrated on the cell surface by SEM-EDX. Mn²⁺ adsorbed to functional groups of the adsorbent was studied by FTIR. The adsorption process of Mn²⁺ showed saturation and followed pseudo–second-order kinetics; was consistent with the homogeneity of the Langmuir model (R² of 0.99); exhibited a Q_max of 62.5 mg g^?1 and a binding energy of 0.018 L mg^?1. The Mn²⁺adsorption was also consistent with the heterogeneity of the Freundlich model by exhibiting a K_f of 1.0 mg g^?1 with an n value of 1.1. Adsorption efficiency of 99% was retained even after a third adsorption-desorption cycle. This is the first report on metal ion adsorption, using Mn²⁺ as an example, by the haloarchaeon Halobacterium sp. GUSF (MTCC3265) in the domain Archaea.     

Bioreactor microbial ecosystems for thiocyanate and cyanide degradation unravelled with genome‐resolved metagenomics

Gold ore processing uses cyanide (CN^?), which often results in large volumes of thiocyanate‐ (SCN^?) contaminated wastewater requiring treatment. Microbial communities can degrade SCN^? and CN^?, but little is known about their membership and metabolic potential. Microbial‐based remediation strategies will benefit from an ecological understanding of organisms involved in the breakdown of SCN^? and CN^? into sulfur, carbon and nitrogen compounds. We performed metagenomic analysis of samples from two laboratory‐scale bioreactors used to study SCN^? and CN^? degradation. Community analysis revealed the dominance of Thiobacillus spp., whose genomes harbour a previously unreported operon for SCN^? degradation. Genome‐based metabolic predictions suggest that a large portion of each bioreactor community is autotrophic, relying not on molasses in reactor feed but using energy gained from oxidation of sulfur compounds produced during SCN^? degradation. Heterotrophs, including a bacterium from a previously uncharacterized phylum, compose a smaller portion of the reactor community. Predation by phage and eukaryotes is predicted to affect community dynamics. Genes for ammonium oxidation and denitrification were detected, indicating the potential for nitrogen removal, as required for complete remediation of wastewater. These findings suggest optimization strategies for reactor design, such as improved aerobic/anaerobic partitioning and elimination of organic carbon from reactor feed.     

Evaluation of tertiary treatment by fungi,enzymatic and photo-Fenton oxidation on the removal of phenols from a kraft pulp mill effluent: a comparative study

Pulp and paper mills generate pollutants associated to their effluents depending upon the type of process, type of the wood materials, process technology applied, management practices, internal recirculation of the effluent for recovery, the amount of water used in the industrial process and type of secondary treatment. This study is the first that reports a simultaneous evaluation of the effects of tertiary treatments by fungi (Rhizopus oryzae and Pleurotus sajor caju), by enzyme (laccase) and by an oxidation process (photo-Fenton) on individual phenols (vanillin, guaiacol, phloroglucinol, vanillic acid and syringic acid) of a Eucalyptus globulus bleached kraft pulp and paper mill final effluent after secondary treatment (BKPME). The tertiary treatments were applied on BKPME samples and in BKPME samples supplemented with extra concentration of each phenol. Tertiary treatments by Rhizopus oryzae and photo-Fenton oxidation were able of complete removal (100%) of phenols on BKPME samples whereas P. sajor caju and laccase were able of 60–85% removal. On BKPME samples with added concentration of each phenol, photo-Fenton was the only treatment capable of total phenols removal (100%), which suggests a great potential for its application.     

Phenol Biodegradation and Metal Removal by a Mixed Bacterial Consortium

This paper reports the tolerance and biodegradation of phenol by a heavy metal–adapted environmental bacterial consortium, known as consortium culture (CC). At the highest tolerable phenol concentration of 1200 mg/L, CC displayed specific growth rate of 0.04 h^?1, phenol degradation rate of 6.11 mg L^?1 h^?1 and biomass of 8.45 ± 0.35 (log₁₀ colony-forming units [CFU]/ml) at the end of incubation. Phenol was degraded via the ortho-cleavage pathway catalyzed by cathechol-1,2-dioxygenase with specific activity of 0.083 (µmol min^?1 mg^?1 protein). The different constituent bacterial isolates of CC preferentially grow on benzene, toluene, xylene, ethylbenzene, cresol, and catechol, suggesting a synergistic mechanism involved in the degradation process. Microtox assay showed that phenol degradation was achieved without producing toxic dead-end metabolites. Moreover, lead (Pb) and cadmium (Cd) at the highest tested concentration of 1.0 and 0.1 mg/L, respectively, did not inhibit phenol degradation by CC. Simultaneous metal removal during phenol degradation was achieved using CC. These findings confirmed the dual function of CC to degrade phenol and to remove heavy metals from a mixed-pollutant medium.     

Degradation of cyanide in agroindustrial or industrial wastewater in an acidification reactor or in a single-step methane reactor by bacteria enriched from soil and peels of cassava

During cassava starch production, large amounts of cyanoglycosides were released and hydrolysed by plant-borne enzymes, leading to cyanide concentrations in the wastewater as high as 200 mg/l. For anaerobic degradation of the cyanide during pre-acidification or single-step methane fermentation, anaerobic cultures were enriched from soil residues of cassava roots and sewage sludge. In a pre-acidification reactor this culture was able to remove up to 4 g potassium cyanide/l of wastewater at a hydraulic retention time (t _HR) of 4 days, equivalent to a maximal cyanide space loading of 400 mg CN⁻ l⁻¹ day⁻¹. The residual cyanide concentration was 0.2–0.5 mg/l. Concentrated cell suspensions of the mixed culture formed ammonia and formate in almost equimolar amounts from cyanide. Little formamide was generated by chemical decay. A concentration of up to 100 mmol ammonia/l had no inhibitory effect on cyanide degradation. The optimal pH for cyanide degradation was 6–7.5, the optimal temperature 25–37 °C. At a pH of 5 or lower, cyanide accumulated in the reactor and pre-acidification failed. The minimal t _HR for continuous cyanide removal was 1.5 days. The enriched mixed culture was also able to degrade cyanide in purely mineralic wastewater from metal deburring, either in a pre-acidification reactor with a two-step process or in a one-step methanogenic reactor. It was necessary to supplement the wastewater with a carbon source (e.g. starch) to keep the population active enough to cope with any possible inhibiting effect of cyanide. Received: 29 April 1998 / Received revision: 8 June 1998 / Accepted: 14 June 1998     

Turn‐off–on chemiluminescence determination of cyanide

A flow injection chemiluminescence (FI–CL) method was developed for the determination of cyanide (CN⁻) based on the recovered CL signal by Cu²⁺ inhibiting a glutathione (GSH)‐capped CdTe quantum dot (QD) and hydrogen peroxide system. In an alkaline medium, strong CL signals were observed from the reaction of CdTe QDs and H₂O₂, and addition of Cu²⁺ could cause significant CL inhibition of the CdTe QDs–H₂O₂ system. In the presence of CN⁻, Cu²⁺ can be removed from the surface of CdTe QDs via the formation of particularly stable [Cu(CN)_n]^(n‐1)– species, and the CL signal of the CdTe QDs–H₂O₂ system was efficiently recovered. Thus, the CL signals of CdTe QDs–H₂O₂ system were turned off and turned on by the addition of Cu²⁺ and CN⁻, respectively. Further, the results showed that among the tested ions, only CN⁻ could recover the CL signal, which suggested that the CdTe QDs–H₂O₂–Cu²⁺ CL system had highly selectivity for CN⁻. Under optimum conditions, the CL intensity and the concentration of CN⁻ show a good linear relationship in the range 0.0–650.0 ng/mL (R² = 0.9996). The limit of detection for CN⁻ was 6.0 ng/mL (3σ). This method has been applied to detect CN⁻ in river water and industrial wastewater with satisfactory results. Copyright © 2014 John Wiley & Sons, Ltd.     

The effect of urea on growth of moulds and biomass yield in solid-state cultivation

Urea, added at 2 to 20 mg/g in solid bran medium supporting growth of Aspergillus oryzae and Rhizopus oligosporus, led to a higher concentration of NH₄ ⁺ and pH but a decrease in biomass production.The authors are with the Department of Food Science and Technology, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, 61000 Ljubljana, Slovenia.     

Synthesis and characterization of phenothiazine sensor for spectrophotometric and fluorescence detection of cyanide

A sensitive and selective phenothiazine-based sensor (PTZ) has been successfully synthesized. The sensor PTZ displayed specific identification of CN⁻ ‘turn-off’ fluorescence responses with a quick reaction and strong reversibility in an acetonitrile:water (90:10, V/V) solution. The sensor PTZ for detecting CN⁻ exhibits the marked advantages of quenching the fluorescence intensity, fast response time (60 s), and low value of the detection limit. The concentration that is authorized for drinking water by the WHO (1.9 μM) is far higher than the detection limit, which was found to be 9.11 × 10⁻⁹. The sensor displays distinct colorimetric and spectrofluorometric detection for CN⁻ anion due to the addition of CN⁻ anion to the electron-deficient vinyl group of PTZ, which reduces intramolecular charge transfer efficiencies. The 1:2 binding mechanism of PTZ with CN⁻ was validated by fluorescence titration, Job's plot, HRMS, ¹H NMR, FTIR analysis, and density functional theory (DFT) investigations, among other methods. Additionally, the PTZ sensor was successfully used to precisely and accurately detect cyanide anions in actual water samples.     

Rationally designed molecules for resurgence of cyanide mitigated cytochrome c oxidase activity

Cytochrome c oxidase (CcOX) containing binuclear heme a₃-Cu B centre (BNC) mechanises the process of electron transfer in the last phase of cellular respiration. The molecular modelling based structural analysis of CcOX – heme a₃-Cu B complex was performed and the disturbance to this complex under cyanide poisoning conditions was investigated. Taking into consideration the results of molecular docking studies, new chemical entities were developed for clipping cyanide from the enzyme and restoring its normal function. It was found that the molecules obtained by combining syringaldehyde, oxindole and chrysin moieties bearing propyl/butyl spacing groups occupy the BNC region and effectively remove cyanide bound to the enzyme. The binding constant of compound 2 with CN^– was 2.3 × 10⁵ M⁻¹ and its ED₅₀ for restoring the cyanide bound CcOX activity in 10 min was 16 µM. The compound interacted with CN^– over the pH range 5–10. The comparison of the loss of enzymatic activity in the presence of CN^– and resumption of enzymatic activity by compound 2 mediated removal of CN^– indicated the efficacy of the compound as antidote of cyanide.     

Transport of Ferrocyanide by Two Eucalypt Species and Sorghum

The wastes from some industrial processes and the tailings from gold mining contain elevated concentrations of cyanide, which reacts with iron in the media to form iron cyanide complexes. This research examined the transport and possible metabolism of ferrocyanide by two native Australian trees, blue mallee and sugar gum, and by sorghum. Hydroponic studies using ¹⁵N-labeled ferrocyanide showed that both tree species transported ferrocyanide into roots and displayed significant increases in ¹⁵N enrichment and concentration with no evidence of phytotoxicity. A subsequent experiment with blue mallee and membrane-transport inhibitors showed that ¹⁵N enrichment was significantly inhibited in the presence of the protonophore carbonyl cyanide m-chlorophenylhydrazone, suggesting that ferrocyanide uptake is mediated partly by H⁺-symporters. A study of the time dependence of ¹⁵N translocation showed a rapid equilibration of ¹⁵N from ferrocyanide in the root of blue mallee, accompanied by a slow increase in shoot ¹⁵N, suggestive of the metabolism of ferrocyanide in plant roots. A similar experiment with sorghum showed a more rapid translocation of ¹⁵N, suggesting that the transport and/or metabolism of ferrocyanide by roots of this species may differ. The results offer additional incentive for the use of these species as vegetative cover over cyanidation wastes and for cyanide phytoremediation.     

Effects of metal quantity and quality to the removal of zinc and copper by two common green microalgae (Chlorophyceae) species

Appearance of metals as pollutants in the environment is an increasing global problem. Microalgae as subjects of biological remediation methods may provide a cost‐effective and environmentally friendly alternative to the removal of metals during wastewater treatment. Despite the high number of data in the topic, there is still little information on how the type and the concentration of the metal affect the process of removal. In this study, correlations among the algal species, quality and quantity of metals and characteristics of metal removal mechanism were investigated at lower metal concentrations (0.2–5.0 mg L^?1) during zinc and copper removal of the green algae Desmodesmus communis and Monoraphidium pusillum. Analyses of the results proved that there is a statistically significant interaction (P < 0.05) between algal species and quality and concentration of the metals, that is, they have a significant effect on the mode and extent of removal. Both metals were mainly extracellularly bound, but at concentrations of 0.2–1.4 mg L^?1, intracellular proportion could exceed the extracellular adsorption. Although there were differences between the two algae, generally copper appeared in a higher intracellular proportion than zinc in the whole studied concentration range. Overall, the quality and initial concentration of the metal is decisive for the way of removal, the knowledge of which is useful for planning post treatment retention times or post treatment processes of the used biomass during wastewater treatment.     

Isolation and Characterization of Phenol-Degrading Soil Bacterium Xanthobacter flavus

A soil bacterium isolated from a contaminated site degraded phenol when provided as the sole carbon and energy source in the medium. The bacterium was identified as Xanthobacter flavus MTCC 9130. This microbial strain was able to tolerate phenol up to 1000 mg L^?1 concentration. The lag phase increased with the increase in phenol concentration. The optimum growth temperature was 37°C. The organism efficiently utilized phenol and could degrade it completely within 120 h when initial concentration was less than 600 mg L^?1. Degradation of phenol was through ortho pathway, enzyme assay through cell-free extract exhibited the presence of catechol 1,2-dioxygenase. The specific activity was 0.146 μ mol min^?1 mg^?1 protein. However, higher concentrations of phenol in the medium had a negative effect on the growth of the bacterium. Hence this ability of Xanthobacter flavus can be effectively used for bioremediation studies of phenol-contaminated sites.     

Enhancement of phenol degradation by free and immobilized mixed culture of Providencia stuartii PL4 and Pseudomonas aeruginosa PDM isolated from activated sludge

Biodegradation of phenol has been investigated using a bacterial consortium consisting of two bacterial isolates; one of them used for the first time in phenol biodegradation. This consortium was isolated from activated sludge and identified as Providencia stuartii PL4 and Pseudomonas aeruginosa PDM (accession numbers KY848366 and MF445102, respectively). The degradation of phenol by this consortium was optimal at pH 7 with using 1500?mg?l^?1 ammonium chloride as a nitrogen source. Interestingly, after optimizing the biodegradation conditions, this consortium was able to degrade phenol completely up to 1500?mg?l^?1 within 58?h. The immobilization of this consortium on various supporting materials indicated that polyvinyl alcohol (PVA)-alginate beads and polyurethane foam (PUF) were more suitable for biodegradation process. The freely suspended cells could degrade only 6% (150?mg?l^?1) of 2500?mg?l^?1 phenol, whereas, the immobilized PVA-alginate beads and the immobilized PUF degraded this concentration completely within 120?h of incubation with degradation rates (q) 0.4839 and 0.5368 (1/h) respectively. Thus, the immobilized consortium of P. stuartii PL4 and P. aeruginosa PDM can be considered very promising in the treatment of effluents containing phenol.