Biodegradation Of Phenol Research Articles

Metabolic profiling of phenol biodegradation by an indigenous Rhodococcus pyridinivorans strain PDB9T N-1 isolated from paper pulp wastewater

In the present study, a phenol degrading actinomycetes strain was isolated from paper pulp wastewater. The isolated strain was identified as Rhodococcus pyridinivorans PDB9TN-1 using 16S rRNA gene sequencing technique, which yielded the complete degradation of 1600 mg l−1 of phenol within 56 h. Moreover, the Rhodococcus species could remove over 97.5% of total organic carbon (TOC) at an initial phenol concentration of 1000 mg l−1. The metabolic profile of phenol biodegradation by the actinomycetes species has been investigated using liquid chromatography–mass spectrometry (LC-MS) and Fourier-transform infrared spectroscopy (FT-IR). The key intermediate products detected in the actinomycetes culture were hydroquinone, protocatechuic acid, beta-carboxycis-cismuconate, maleyl acetate, 4–oxalocrotonic acid and 3-fumarylpyruvic acid. Further, a tentative oxalocrotonic acid pathway has been proposed on the basis of the detected intermediate products. The culture medium constituents are highly indispensable for the microbial growth, enzyme and other cellular metabolic activities associated with phenol biodegradation. Therefore, the effect of media components were modelled with the help of response surface methodology (RSM) and central composite design (CCD). A reliable quadratic model was established which predicted the degradation efficiency as high as 99.5% with an appreciable correlation coefficient (R2) of 0.98. Moreover, phenol degradation efficiency was improved with concentrations beyond the central values for all media components except K2HPO4 and NaCl.

Biodegradation Kinetic Studies of Phenol and p-Cresol in a Batch and Continuous Stirred-Tank Bioreactor with Pseudomonas putida ATCC 17484 Cells

The biodegradation of phenol, p-cresol, and phenol plus p-cresol mixtures was evaluated using Pseudomonas putida ATCC 17484 in aerobic batch reactors. Shake-flask experiments were performed separately using growth medium with initial nominal concentrations of phenol (50–600 mg L−1) and p-cresol (50–600 mg L−1) as well as phenol (50–600 mg L−1) plus p-cresol (50–600 mg L−1). The complete degradation of phenol and p-cresol was achieved within 48 h and 48–56 h, respectively, for all initial concentrations of phenol and p-cresol. The maximum cell growth rate using phenol (μmax,P = 0.45 h−1) was much faster than that using p-cresol (μmax,C = 0.185−1 h). The larger Ki value for phenol (310.5 mg L−1) revealed that the P. putida cells had a higher resistance to phenol inhibition compared with p-cresol (243.56 mg L−1). A mixture of phenol and p-cresol in batch experiments resulted in the complete removal of phenol within 52–56 h for initial phenol concentrations of 50–500 mg L−1. The time needed to remove p-cresol completely was 48–56 h for initial p-cresol concentrations of 50–500 mg L−1. In the continuous-flow immobilized cells reactor, the degradation efficiency for phenol and p-cresol was 97.6 and 89.1%, respectively, at a stable condition.

Utilization of Phenol as Carbon Source by the Thermoacidophilic Archaeon Saccharolobus solfataricus P2 Is Limited by Oxygen Supply and the Cellular Stress Response.

Present in many industrial effluents and as common degradation product of organic matter, phenol is a widespread compound which may cause serious environmental problems, due to its toxicity to animals and humans. Degradation of phenol from the environment by mesophilic bacteria has been studied extensively over the past decades, but only little is known about phenol biodegradation at high temperatures or low pH. In this work we studied phenol degradation in the thermoacidophilic archaeon Saccharolobus solfataricus P2 (basonym: Sulfolobus solfataricus) under extreme conditions (80°C, pH 3.5). We combined metabolomics and transcriptomics together with metabolic modeling to elucidate the organism’s response to growth with phenol as sole carbon source. Although S. solfataricus is able to utilize phenol for biomass production, the carbon source induces profound stress reactions, including genome rearrangement as well as a strong intracellular accumulation of polyamines. Furthermore, computational modeling revealed a 40% higher oxygen demand for substrate oxidation, compared to growth on glucose. However, only 16.5% of oxygen is used for oxidation of phenol to catechol, resulting in a less efficient integration of carbon into the biomass. Finally, our data underlines the importance of the phenol meta-degradation pathway in S. solfataricus and enables us to predict enzyme candidates involved in the degradation processes downstream of 2-hydroxymucconic acid.

Biodegradation of Phenol by Bacillus simplex: Characterization and Kinetics Study

Phenol is one of the main pollutants that have a serious impact on the environment and can even be very critical to human health. The biodegradation of phenol can be considered an increasingly important pollution control process. In this study, the degradation of phenol by Bacillus simplex was investigated for the first time under different growth conditions. Six different initial concentrations of phenol were used as the primary substrate. Culture conditions had an important effect on these cells' ability to biodegrade phenol. The best growth of this organism and its highest biodegradation level of phenol were noticed at pH 7, temperature 28 °C, and periods of 36 and 96 h, respectively. The GC-MS analysis of the bacterial culture sample revealed that further degradation of the catechol by 1,2-dioxygenase produce a cis, cis-mucconic acid via ortho-pathway and/or by 2,3-dioxygenase into 2-hydroxymucconic semialdehyde via meta-pathway. The highest biodegradation rate was perceived at 700 mg/L initial phenol concentration. Approximately 90% of the phenol (700 mg / L) was removed in less than 96 hours of incubation time. It was found that the Haldane model best fitted the relationship between the specific growth rate and the initial phenol concentration, whereas the phenol biodegradation profiles with time could be adequately described by the modified Gompertz model. The obtained parameters from the Haldane equation are: 1.05 h−1, 9.14 ppm, and 329 ppm for Haldane's maximum specific growth rate, the half-saturation coefficient, and the Haldane’s growth kinetics inhibition coefficient, respectively. The Haldane equation fitted the experimental data by minimizing the sum of squared error (SSR) to 1.36 X 10-3.

Biodegradation of phenolic compounds using immobilized Pseudomonas aeruginosa on granular activated carbon: Effect of immobilization, kinetic study and microbial regeneration

Phenol and its derivatives are one of the major pollutants present in industrial effluents. In this work, Pseudomonas aeruginosa (ATCC 9027) has been effectively used to carry out biodegradation of phenol, 3-aminophenol, and catechol. In order to develop an industrially viable technology, P. aeruginosa has been immobilized on granular activated carbon (GAC). The biofilm thickness was found in the range 14 to 34 μm. The adsorbed P. aeruginosa on the GAC is found to be efficient for bio-degradation of the phenolic compounds and in addition they also helped in regeneration of the activated carbon systems which in turn reduce the operability cost. The extent of bio-regeneration varied between 33-66%. Haldane’s growth kinetic equation is found to be suitable to fit the specific growth rate data of P. aeruginosa.

<em>Acinetobacter</em> spp. and <em>Stenotrophomonas acidaminiphila</em> strain pars1396 isolated from landfill soil and industrial wastewater as potential candidates for phenol biodegradation

<em>Acinetobacter</em> spp. and <em>Stenotrophomonas acidaminiphila</em> strain pars1396 isolated from landfill soil and industrial wastewater as potential candidates for phenol biodegradation

Effect of lignite activated coke packing on power generation and phenol degradation in microbial fuel cell treating high strength phenolic wastewater

Microbial fuel cell (MFC) is commonly used for easily biodegradable substances, yet its application for high strength phenolic wastewater treatment remains a challenge. This study incorporates lignite activated coke (LAC) into MFC to alleviate the inhibition of phenol and facilitate power generation of MFC. The power generation and phenol degradation in both LAC-MFC and control MFC were investigated at phenol concentrations of 500 mg/L, 700 mg/L and 1000 mg/L. The results showed that the maximum power density in LAC-MFC was maintained in the range of 252.3–278.7 mW/m2 when the phenol concentration increased from 500 mg/L to 1000 mg/L, whereas it was decreased from 246.5 mW/m2 to 167.5 mW/m2 in control-MFC. This corresponds to a high phenol removal of 89.4% to 94.5% in LAC-MFC but a significant decrease from 80.7% to 50.8% in control MFC. The inhibition coefficient (Ki) calculated from Haldane inhibition model decreased by 24.3% in LAC-MFC compare with control MFC, suggesting that the stress of high concentrations of phenol on MFC was largely relieved. In addition, the phenol degradation intermediate products of 2-hydroxymuconic semialdehyde, 4-hydroxybenzoic acid, 4-hydroxy-3-methylbenzoic acid were apparently lower in LAC-MFC than control MFC, indicating that the biodegradation of phenol was enhanced in LAC-MFC. High-throughput sequencing analysis revealed that Pseudomonas, Desulfuromonas, and Hydrogenophaga might be associated with phenol degradation and power generation in LAC-MFC. Because of its effectiveness in alleviating the toxic effects of phenol, LAC packing is a promising MFC technology for high strength phenolic wastewater treatment.

Effect of Fe3O4 nanoparticles exposure on the treatment efficiency of phenol wastewater and community shifts in SBR system

Increasing magnetic Fe3O4 nanoparticles (Fe3O4 NPs) application has aroused concern about its potential environmental toxicity. During acute and chronic exposure, key enzymes involved in phenol biodegradation were promoted at 0–600 mg/L Fe3O4 NPs, while were inhibited at 800 mg/L Fe3O4 NPs, correspondingly affected phenol degradation efficiency. Lactic dehydrogenase (LDH) increased when Fe3O4 NPs exceeded 600 mg/L, indicated the more severe cell rupture at high Fe3O4 NPs concentration. At the same Fe3O4 NPs concentration, the removal of EPS further inhibited key enzymes, decreased phenol degradation, and increased LDH, indicating that the existence of EPS relieved the adverse effects on microorganisms. Spectroscopic analysis showed that protein and polysaccharide associated bonds in EPS decreased at 0–600 mg/L Fe3O4 NPs, while increased when Fe3O4 NPs exceeded 600 mg/L, which was in accordance with EPS content. Biopolymer-degrading and phenol-degrading genera increased at 0–600 mg/L Fe3O4 NPs, while decreased at Fe3O4 NPs exceeded 600 mg/L, which conformed to EPS content and phenol degradation efficiency.

Enhanced phenol degradation under different shock-stress in LAC/AS system: The combination effects of LAC toxicity mitigation and microbial community shift

The lignite activated coke-facilitated activated sludge (LAC/AS) process has proved to be an effective method for increase of phenol biodegradability, yet the interactions between LAC toxicity mitigation and microbial community shift remain unclear. In this study, the phenol degradation rate under different shock-stress for 51 days were investigated. LAC/AS system can tolerate higher phenol shock stress but phenol removal rate starts to descend at 200 mg/L. The system settling performance deteriorated as the filamentous bulking appeared after 40 days but the phenol removal rate was maintained. The results indicated that the microbial community tend to shift for phenol biodegradation when the effect of LAC toxicity mitigation subdued. However, the SVI increased sharply from 40 to 226 mL/g in a relatively long operation period along with the increase of floc size and reduction of TB EPS. Flavobacterium and Bacteroides were the dominated species in the LAC/AS bulking system, correlating to the sustained phenol removal. This work enhances our understanding on the interactions between LAC and microbial community in LAC/AS system, which can be employed for further optimizing LAC/AS technology.

Biodegradation of polycyclic aromatic hydrocarbons, phenol and sodium sulfate by Nocardia species isolated and characterized from Iranian ecosystems

Anthropogenic pollutants are known to have adverse effect on ecosystem, biodiversity and human health. Bioremediation is an option that has been widely used to remediate organic contaminants and reduce the risk of these hazardous materials. Microorganisms are readily available to screen and can be rapidly characterized to be applied in many extreme environmental conditions. Actinomycetes have a great potential for the production of bioactive secondary metabolites which have biodegradation activity. This study aimed to screen and characterize Nocardia species with biodegradation potential from diverse Iranian ecosystems. The isolates were screened from 90 collected environmental samples, identified and characterized using conventional and molecular microbiological methods including the PCR amplification and sequencing analysis of 16S rRNA and rpoB genetic markers. Growth rate in presence of pollutants, chromatography, Gibbs and turbidometric methods were used to determine bioremediation ability. A total of 19 Nocardia isolates were recovered from the cultured samples (21.1%) that belonged to 10 various species. The most prevalent Nocardia species was N. farcinica; 4 isolates (21%), followed by N. cyriacigeorgica and N. cashijiensis like; 3 isolates each (15.7%) and N. asteroides and N. kroppenstedtii; 2 isolates each (10.5%). Our results showed that various Nocardia species have great potential for bioremediation purposes, although they have not received much attention of the scholars for such significant usage.

Electrical stimulation on biodegradation of phenolics in a novel anaerobic–aerobic-coupled upflow bioelectrochemical reactor

• An anaerobic–aerobic-coupled upflow bioelectrochemical reactor was constructed. • Intermittent electrical stimulation mode promoted phenolics degradation. • Aerobic cathodic chamber showed high contribution to the phenolics removal. • Specific microbes were enriched in the cathodic and anodic chambers of the system. Phenolics were widespread in the effluents of coal gasification plants and oil refineries processes, while the impact of electrical stimulation on phenolics degradation in the combined biological processes remained unclear. Here, a novel anaerobic–aerobic–coupled upflow bioelectrochemical reactor (AO-UBER) was used to treat phenol-containing synthetic wastewater and simulated phenolic wastewater. The AO-UBER could treat phenolic compounds effectively via electrical stimulation. Phenol and total phenol removal efficiencies in the intermittently electrically stimulated system with a hydraulic retention time of 6 h were about 22.6% and 31.1%, respectively, higher than that in the biological system not exposed to voltage. The contribution of the aerobic cathodic chamber to the removal of phenolic compounds was higher than that of the anaerobic anodic chamber under the intermittent voltage application mode. High-throughput sequencing analysis indicated that electrical stimulation selectively enriched Acinetobacter , Cloacibacterium , Acidovorax, and Zoogloea in the phenol-containing synthetic wastewater treatment process, and Rhodococcus , Achromobacter , Chryseobacterium, and PSB-M-3 in the simulated phenolic wastewater treatment process. These results demonstrate that the AO-UBER under intermittent voltage application mode holds good potential for efficient phenolic wastewater treatment.

Biodegradation of phenol by a highly tolerant strain Rhodococcus ruber C1: Biochemical characterization and comparative genome analysis

A novel phenol-degrading strain was isolated and identified as Rhodococcus ruber C1. The degradation analysis shows that 1806 mg/L of phenol can be completely degraded by strain C1 within 38 h, and the maximum specific growth rate (μmax=1.527 h−1) and maximum specific phenol degradation rate (qmax=3.674 h−1) indicate its excellent phenol metabolism capability. More importantly, phenol can be degraded by strain C1 in the temperature range of 20–45 °C within 72 h, and with longer degradation time, phenol can be completely degraded even at 10, 15 and 50 °C. The whole genome of strain C1 was sequenced, and a comparative genome analysis of strain C1 with 36 other genomes of Rhodococcus was performed. A remarkable gene family expansion occurred during the evolution of Rhodococcus, and a comprehensive evolutionary picture of Rhodococcus at genomic level was presented. Moreover, the copy number of genes involved in phenol metabolism was compared among genus Rhodococcus, and the results demonstrate high phenol degradation capability of strain C1 at genomic level. These findings suggest that Rhodococcus ruber C1 is a bacterium capable of degrading phenol efficiently in the temperature range of 10–50 °C.

Statistical optimisation for enhancement of phenol biodegradation by the Antarctic soil bacterium Arthrobacter sp. strain AQ5-15 using response surface methodology

Aim: Effective bioremediation requires optimisation of conditions under which the process takes place. In this study, an Antarctic soil bacterium, Arthrobacter sp. strain AQ5-15, was evaluated for phenol biodegradation under statistically optimised conditions. Methodology: The composition of degradation media and the culture conditions for this study were determined according to the experimental requirements obtained from Plackett-Burman factorial design (PB) and Box-Wilson Central Composite Design (CCD), respectively. Phenol degradation was monitored by 4-aminoantipyrine colorimetric assay and bacterial growth was quantified by measuring optical density (OD600 nm) at 72 hr. Results: A preliminary screening experiment using the Plackett-Burman design indicated that all the factors screened (ammonium sulphate concentration, sodium chloride concentration, pH and temperature) had significant influence on degradation performance. Response Surface Methodology was then utilised to further optimise the phenol-degrading process using Central Composite Design. The maximum percentage of phenol degradation achieved with CCD was 99.42%, under medium conditions of 0.15 g l-1 (NH4)2SO4, 0.13 g l-1 NaCl, pH 7.25 and incubation at 15°C for 72 hr. The strain could degrade phenol when exposed to an initial concentration of up to 1.5 g l-1 under these optimised conditions. Interpretation: The tolerance and degradation characteristics of strain AQ5-15 suggest that it has potential application in bioremediation of polluted sites and in the treatment of relatively cool water bodies contaminated with phenol.

Impact of electrical stimulation modes on the degradation of refractory phenolics and the analysis of microbial communities in an anaerobic-aerobic-coupled upflow bioelectrochemical reactor

An electrically stimulated anaerobic–aerobic coupled system was developed to improve the biodegradation of refractory phenolics. Expected 4-nitrophenol, 2, 4-dinitrophenol, and COD removals in the system with aerobic cathodic and anaerobic anodic chambers were approximately 53.7%, 45.4%, 22.3% (intermittent mode) and 37.9%, 19.8%, 17.3% (continuous mode) higher than that in the control system (26.0 ± 6.4%, 30.7 ± 7.1%, 49.8 ± 3.0%). 2, 4-dichlorophenol removal in the system with aerobic anodic and anaerobic cathodic chambers was approximately 28.5% higher than that in the control system (71.4 ± 5.7%). The contribution of the aerobic cathodic/anodic chambers to the removal of phenolic compounds was higher than that of the anaerobic cathodic/anodic chambers. The species related to phenolic biodegradation (Rhodococcus, Achromobacter, PSB-M-3, and Sphingobium) were enriched in the cathodic and anodic chambers of the system. These results showed that intermittent electrical stimulation could be a potential alternative for the efficient degradation of refractory phenolics.

Acclimation of Isochrysis galbana Parke (Isochrysidaceae) for enhancing its tolerance and biodegradation to high-level phenol in seawater

Marine microalgae with high removal efficiency of phenol are needed for the remediation of polluted seawater in cases involving phenol spills. To achieve this purpose, adaptive laboratory evolution (ALE) was performed by a microalga Isochrysis galbana Parke MACC/H59, which is capable of degrading phenol at concentrations of less than 100 mg L−1 in 4 d. Two acclimation conditions were used: (i) 90 d at 100 mg L−1 phenol, and (ii) 90 d at 100 mg L−1 phenol followed by another 90 d at 200 mg L−1 phenol. By doing so, two strains (PAS-1 and PAS-2) could be obtained respectively. They grew rapidly at phenol concentrations up to 200 mg L−1 and 300 mg L−1, respectively, with a specific growth rate 2.52–3.40 times and 1.93–3.23 times that of the control (without phenol). Also, both strains had a higher removal capacity of phenol than the unacclimated alga. Phenol at an initial concentration of 200 mg L−1 was completely removed in 5 d thereby. For 300 mg L−1 phenol, a removal efficiency of 92% was achieved in 10 days by using PAS-2, with a removal rate constant of 30.01 d−1 (about twice that of PAS-1) and a half-life of 4.90 d (about half that of PAS-1), showing that a better strain may be obtained by extending the acclimation time. The enhancement of phenol biodegradation can be explained by the elevated activity of phenol hydroxylase (PH) in both strains. These results indicated that ALE could be an efficient tool used to enhance the tolerance and biodegradation of marine microalgae to phenol in seawater.

Peroxidase from waste cabbage (Brassica oleracea capitata L.) exhibits the potential to biodegrade phenol and synthetic dyes from wastewater

Peroxidases are well known for their ability to biodegrade some recalcitrant organic pollutants like phenol and their derivatives resulting in a reduction in their toxicity. The present study was designed to extract, characterize, and evaluate the potential of partially purified peroxidase from discarded and decaying waste cabbage leaves in the biodegradation of phenol and some common synthetic azo dyes. This was done by first partially purifying the crude extract of waste cabbage peroxidase (WCP) using ammonium sulfate precipitation, dialysis, and gel filtration chromatography. Thereafter, the experimental determination of protein concentration, peroxidase activity, and biodegradation of phenol and azo dyes was done spectrophotometrically. The results showed a purification fold of 87.65 with a 34.92% yield. The partially purified peroxidase had its optimum activity at temperature 30 °C, pH 5.5 while showing broad substrate preference with ABTS been the substrate. The stability studies also showed that WCP was stable over a wide range of pH (4.0–7.0) and 41% of its original activity was retained at 80 °C indicating that it is a thermostable enzyme. The kinetic data of WCP showed Km values of 1.24, 17.89, and 19.24 mM and Vmax values of 1111.11, 909.09, and 588.24 mM /minutes for ABTS, guaiacol, and o-dianisidine respectively. Three metal ions, Hg2+, Cu2+, Ni2+, organic solvent (acetone), EDTA, and urea inhibited peroxidase activity; whereas Mn2+ and Zn2+ showed slight activation. The partially purified WCP exhibited high efficiency for the biodegradation of synthetic azo dyes and phenol at the lab-scale. After 48 h incubation, the waste cabbage peroxidase efficiently catalyzed the decolorization of tested azo dyes at varying degrees; azo blue 5, azo purple, azo yellow 6, and citrus red 2, with a percentage decolorization of 85.1, 69.1, 46.2 and 42.9%, respectively. The waste cabbage peroxidase also shows up to 91.1% efficiency for degradation of phenol in aqueous solution after 60 min. Findings from this study provide promising evidence on the possibility of utilizing/recycling a readily abundant waste cabbage to useful bioproducts like peroxidase enzyme with the ability to biodegrade azo dyes and phenol at a small scale in the laboratory. Moreover, the findings from this study increase the prospect of waste cabbage peroxidase for the treatment of industrial effluents containing dyes and phenolic pollutants. The approach of transforming waste from one source into a useful biocatalyst that can potentially be exploited to treat waste pollutants from a different source offers a chain of green technology.

Biodegradation of phenol by Klebsiellaoxytocaisolated from oil contaminated environments

The degradation of phenol by microorganisms in the soil is an important method through which these materials are removed from the environment, thus reducing environmental pollution. Biodegradation by bacterial species provides unique opportunities to destroy or convert phenolic compounds into other less toxic compounds. In this study, two Klebsiella oxytoca isolates were selected from petroleum contaminated soils using mineral salts medium supporting with phenol as the only carbon source.The isolates were identified by microscopic, morphological, and biochemical approaches, and their capabilities of biodegrading phenol were analyzed by 4-aminoantipyrine assay. The results showed that the selected Klebsiella oxytoca isolates were able to remove 100% of phenol even at a the highest used concentration(500 mg / L).The results of the current study indicate the possibility of using Klebsiella oxytoca in bioremediation of phenol contaminated environments.

Characterisation of the Contaminants Generated from a Large-Scale Ex-Situ Underground Coal Gasification Study Using High-Rank Coal from the South Wales Coalfield

This paper presents an analysis of contaminants generated from large-scale, laboratory-based, underground coal gasification (UCG) experiments using a high-rank coal from the South Wales Coalfield. The experiments were performed at atmospheric and elevated pressures (30 bar) by varying the oxidants’ composition. The experiments were designed to predict the amount of produced water and contaminants generated at each stage of the operating conditions. The mass balance of water supplied and produced in the experiments was accounted for. Chemical analyses of produced water, char and ash contents were performed to quantify the inorganic and organic chemical parameters. Most of the contaminant concentrations in the produced water from the 30-bar pressure experiment were lower than the concentrations generated from the atmospheric pressure experiment. The measured concentrations of the inorganic chemical species and the inorganic parameters of the coal seam water from the South Wales Coalfield were used in theoretical calculations to predict the dominant equilibrium species concentrations in a hypothetical scenario of effluent contaminated groundwater. The biodegradation of organic contaminants such as phenol, benzene and sorbed fractions of inorganic contaminants from the produced water on iron oxide in the ash residue was predicted using existing biotransformation kinetics and surface complexation models, respectively. The biodegradation of phenol and benzene would be a slow process even at optimum conditions and the iron oxide left in the cavity can act as a sorbent for a few inorganic species. The evidence from the present study suggests future work towards (i) developing an appropriate water treatment process during gas cleaning, (ii) operational procedure (pressure and proportions of oxidant) and (iii) developing UCG-specific experimental prediction of contaminant transportation and transformation kinetics.Graphical abstract

Optimization of Cultural and Physical Parameters for Phenol Biodegradation by Newly Identified Pseudomonas sp. AQ5-04

Phenol is widely used by many industries and it is one of the highly toxic environ - mental pollutants. Bioremoval is one of the most effective methods to remove phenol compared to other physio-chemical methods. Identification was carried out using 16s rRNA sequencing. Mineral salt media with 0.5 g/L phenol as the sole source of carbon. Factors influencing phenol degradation were optimised via one-factor-at-a-time and response surface methodology. Optimum degradation was achieved at pH 7.5, the temperature of 30°C and ammonium sulphate at 0.4 g/L. Using Response surface methodology the incubation period was reduced to 36 h compared to the OFAT approach where it takes 72 hours. The effect of 10 heavy metals at various concentrations was tested. The optimum values used for tempe - rature, pH, ammonium sulphate and salinity for both the OFAT and RSM have correlated with the only pH displayed the slighted difference of 7.0 for OFAT and 7.5 for RSM. This shows the closest optimum conditions for both methods. The strain is also resistance to some heavy metals usually found in polluted environ - ments together with phenol. Therefore, it can be clearly stated that Pseudomonas sp. strain AQ5-04 is the potential candidate for phenol bioremediation and further studies in the field of bioremediation. The bacterium can degrade phenol in the presence of between 1 to 3 ppm of the heavy metals As, Cd, Co, and Zn while growth and degradation were inhibited by Hg, Ag, Cu and Ni at 1 ppm. The isolate is a potential strain for further bioremediation studies.

Biodegradation of phenol and dyes with horseradish peroxidase covalently immobilized on functionalized RGO-SiO2 nanocomposite

Horseradish peroxidase (HRP) was immobilized onto a functionalized reduced graphene oxide-SiO2 through the covalent bonding process. By using scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR), the formed nanocomposites were characterized. The kinetic parameters including the catalytic constant, kcat, and the catalytic efficiency, kcat/Km, increased 5.5 and 6 times, respectively, after immobilization. The circular dichroism analysis demonstrated that the α-helical content increased from 39% to 46% after immobilization. The immobilization improved the reusability of HRP as 70% of initial activity retained after 10 cycles. Due to the buffering effect, the immobilized HRP was less sensitive to pH changes as compared to the free HRP. At temperature 40 °C and during 90 min, the immobilized HRP retained 90% of the initial activity while 70% of initial activity remained for the free HRP. After 35-day storage, no reduction in the activity was observed for the immobilized HRP. The removal efficiency for phenol concentration (2500 mg/L) obtained 100% and 50% for the immobilized and free HRP, respectively. The results showed that the immobilized HRP promoted the dyes decolorization from 2-fold until 26-fold as compared to the free HRP. The decolorization efficiencies reached 100% for most dyes in the case of immobilized HRP.