Biodegradation Of Phenolic Compounds Research Articles

Immobilization of laccase on epoxy-functionalized silica and its application in biodegradation of phenolic compounds

A novel method of laccase immobilization on epoxy-functionalized silica particles was developed. Laccase from Myceliophthora thermophila was covalently immobilized onto epoxy-functionalized matrix by nucleophilic attack of amino groups of laccase to epoxy groups of the support. The enzyme loading on the support was about 30 mg/g under the optimum conditions (pH 4.5, 24 h). The effect of pH, temperature and organic solvent on immobilized enzyme activity was determined and compared with those of free enzyme. In general the immobilized enzyme was found to be stabilized compared to the free enzyme. Lineweaver-Burk plots were used to calculate kinetic parameters for ABTS oxidation. KM values were 24.0 and 25.3 μM while vmax values were 10.0 and 1.6 μM min−1 for free and immobilized laccase, respectively. The performance of the biocatalyst was evaluated by the degradation of phenolic compounds including phenol, p-chlorophenol and catechol. The removal efficiency of catechol by immobilized laccase was about 95% after 2 h.

Biodegradation of phenol and its derivatives by engineered bacteria: current knowledge and perspectives.

Biodegradation of phenolic compounds is a promising alternative to physical and chemical methods used to remove these toxic pollutants from the environment. The ability of various microorganisms to metabolize phenol and its derivatives (alkylphenols, nitrophenols and halogenated derivatives) has therefore been intensively studied. Knowledge of the enzymes catalyzing the individual reactions, the genes encoding these enzymes and the regulatory mechanisms involved in the expression of the respective genes in bacteria serves as a basis for the development of more efficient degraders of phenols via genetic engineering methods. Engineered bacteria which efficiently degrade phenolic compounds were constructed in laboratories using various approaches such as cloning the catabolic genes in multicopy plasmids, the introduction of heterologous genes or broadening the substrate range of key enzymes by mutagenesis. Efforts to apply the engineered strains in in situ bioremediation are problematic, since engineered strains often do not compete successfully with indigenous microorganisms. New efficient degraders of phenolic compounds may be obtained by complex approaches at the organism level, such as genome shuffling or adaptive evolution. The application of these engineered bacteria for bioremediation will require even more complex analysis of both the biological characteristics of the degraders and the physico-chemical conditions at the polluted sites.

KINETIC PARAMETERS OF PHENOL BIODEGRADATION WITH DIFFERENT MICROORGANISMS: A REVIEW

Most industries release wastewater contains high concentrations of phenol which is toxic and contaminating the environment. Biological treatments are preferable for the phenolic compounds treatment. This review aims to investigate the impacts of temperatures, pH, and concentration of substrate on the phenolic compounds biodegradation, to compare the kinetic parameters of different microorganisms, and to discuss the different between the kinetic parameters of aerobic and anaerobic treatment. The review showed that most of the phenol biodegrading bacteria are P. Putida species and mixed cultures but P. Putida has a better adaptation to phenol biodegradation. The values of µmax and Ks in anaerobic process are smaller than the values attained in aerobic process. The optimum temperature to acclimatize bacteria to the phenol substrate is 30 oC while the optimum pH condition is between 6.5 and 7.5. As the phenol concentration was increased, there was an increase in the values of the Ks and even when concentration is low; phenols have a significant inhibitory impact on (μ). The values of Ki for phenol degradation for P. putida species were higher than the values of Ki of mixed cultures. The highest Ki value for the phenol degrading among P.Putida species was 1185.8 mg/L and the highest Ki value among mixed cultures was 648.1 mg/L and the highest Ki value among the other species was 2434.7 mg/L.

Towards improved adsorption of phenolic compounds by surface chemistry tailoring of silica aerogels

The high toxicity/volatility and low biodegradation of phenolic compounds are serious concerns in terms of environmental and health impact—their recommended max. value for drinking water is 0.005 mg/L. They are usually removed from effluents by adsorption, but they show a complex interaction behavior with adsorbents, because the hydroxyl group and the hydrophobic aromatic ring are very close. In this work, the versatility of Si chemistry was explored to tailor the surface chemistry of silica aerogels and improve their adsorption performance towards phenolic compounds. Methyltrimethoxysilane and tetramethylorthosilicate were combined to adjust the hydrophobicity of the obtained aerogels. In the next stage, β-cyclodextrin, with its highly hydrophobic cavity, was grafted into the gels to improve the capturing of aromatic rings. For a sustainable linkage of β-cyclodextrin to silica, the methyltrimethoxysilane/tetramethylorthosilicate precursor system was modified by adding an epoxy functionalized silane. A first screening of the adsorption performance shows a 1.5–2-fold increase of the adsorption capacity and removal efficiencies of the epoxy-cyclodextrin-modified aerogel toward phenol and p-cresol when compared to aerogel counterpart without modification. Freundlich isotherm model was the most suitable to describe the equilibrium data of aerogels with or without β-cyclodextrin, with the curves showing favorable profiles, more evident in the case of aerogels with β-cyclodextrin. Apart from the improving of the sorption capacity for phenolic compounds (achieving a maximum of 60 mg g−1 in the case of p-cresol), the utilization of the biodegradable β-cyclodextrin moiety obtained from natural and sustainable resources is a further asset of the epoxy-cyclodextrin-modified aerogel.

Bacterial community structure within an activated sludge reactor added with phenolic compounds.

Biodegradation of phenolic compounds in bioreactors is well documented, but the changes in the bacterial populations dynamics during degradation were not that often. A glass bubble column used as reactor was inoculated with activated sludge, spiked with 2-chlorophenol, phenol and m-cresol after 28days and maintained for an additional 56days, while the 16S rRNA gene from metagenomic DNA was monitored. Proteobacteria (68.1%) dominated the inoculum, but the bacterial composition changed rapidly. The relative abundance of Bacteroidetes and Firmicutes decreased from 4.8 and 9.4 to <0.1 and 0.2% respectively, while that of Actinobacteria and TM7 increased from 4.8 and 2.0 to 19.2 and 16.1% respectively. Phenol application increased the relative abundance of Proteobacteria to 94.2% (mostly Brevundimonas 17.6%), while that of Bacteroidetes remained low (1.2%) until day 42. It then increased to 47.3% (mostly Leadbetterella 46.9%) at day 84. It was found that addition of phenolic compounds did not affect the relative abundance of the Alphaproteobacteria initially, but it decreased slowly while that of the Bacteroidetes increased towards the end.

Enhanced biodegradation of phenolic compounds in landfill leachate by enriched nitrifying membrane bioreactor sludge

The role of autotrophic nitrification on the biodegradation of toxic organic micro-pollutants presented in landfill leachate was assessed. A two-stage MBR system consisting of an inclined tube incorporated anoxic reactor followed by aerobic submerged membrane reactor was operated under long sludge age condition in which nitrifying bacteria could be enriched. During the reactor operation, organic removal efficiencies were more than 90% whereas phenolic compounds including bisphenol A (BPA) and 4-methyl-2,6-di-tert-butylphenol (BHT) were removed by 65 and 70% mainly through biodegradation in the aerobic reactor even at high feed concentrations of 1000μg/L for both compounds. Batch experiments revealed that enriched nitrifying sludge with nitrifying activities could biodegraded 88 and 75% of BPA and BHT, largely improved from non-nitrifying sludge and enriched nitrifying sludge with the presence of inhibitor. The first-order kinetic rates of BHT and BPA removal were 0.0108 and 0.096h−1, also enhanced by 44% from the non-nitrifying sludge.

Biodegradation of phenolic compounds and their metabolites in contaminated groundwater using microbial fuel cells

This is the first study demonstrating the biodegradation of phenolic compounds and their organic metabolites in contaminated groundwater using bioelectrochemical systems (BESs). The phenols were biodegraded anaerobically via 4-hydroxybenzoic acid and 4-hydroxy-3-methylbenzoic acid, which were retained by electromigration in the anode chamber. Oxygen, nitrate, iron(III), sulfate and the electrode were electron acceptors for biodegradation. Electro-active bacteria attached to the anode, producing electricity (~1.8mW/m2), while utilizing acetate as an electron donor. Electricity generation started concurrently with iron reduction; the anode was an electron acceptor as thermodynamically favorable as iron(III). Acetate removal was enhanced by 40% in the presence of the anode. However, enhanced removal of phenols occurred only for a short time. Field-scale application of BESs for in situ bioremediation requires an understanding of the regulation and kinetics of biodegradation pathways of the parent compounds to relevant metabolites, and the syntrophic interactions and carbon flow in the microbial community.

Two-phase biodegradation of phenol in trioctylphosphine oxide impregnated hollow fiber membrane bioreactor

A hollow fiber membrane bioreactor using trioctylphosphine oxide (TOPO) impregnated in polypropylene hollow fiber membranes was developed for two-phase biodegradation of phenol using Pseudomonas putida ATCC 11172. Scanning electron microscopy revealed white deposits of TOPO impregnated non-uniformly within the cross sections and surfaces of the membranes. The extractant impregnated membranes exhibited high adsorption capacity and rates, whereas biodegradation of 800–2500mg/L phenol at 200mL volume in the extractant impregnated hollow fiber membrane bioreactor (EIHFMB) was characterized by high cell growth and biodegradation rates. For example, 1000mg/L phenol was completely degraded within 12h at a specific growth rate of 0.73h−1 while the biomass yield and average biodegradation rate were 0.31g/g and 86mg/Lh, respectively. The biodegradation capacity and rate in the EIHFMB were improved by increasing the effective length of the fibers by 50%, as demonstrated during the biodegradation of 3000mg/L phenol. The adsorption/desorption rates were also enhanced with increasing aqueous phase flow rate. EIHFMB performance remained unchanged over 400h of operation under various operating conditions suggesting the stability of TOPO impregnation within the membrane. These results indicate the use of EIHFMB as a promising technology in solvent-free two-phase biodegradation of phenolic compounds.

Diversity of Planktonic and Attached Bacterial Communities in a Phenol-Contaminated Sandstone Aquifer

Polluted aquifers contain indigenous microbial communities with the potential for in situ bioremediation. However, the effect of hydrogeochemical gradients on in situ microbial communities (especially at the plume fringe, where natural attenuation is higher) is still not clear. In this study, we used culture-independent techniques to investigate the diversity of in situ planktonic and attached bacterial communities in a phenol-contaminated sandstone aquifer. Within the upper and lower plume fringes, denaturing gradient gel electrophoresis profiles indicated that planktonic community structure was influenced by the steep hydrogeochemical gradient of the plume rather than the spatial location in the aquifer. Under the same hydrogeochemical conditions (in the lower plume fringe, 30 m below ground level), 16S rRNA gene cloning and sequencing showed that planktonic and attached bacterial communities differed markedly and that the attached community was more diverse. The 16S rRNA gene phylogeny also suggested that a phylogenetically diverse bacterial community operated at this depth (30 mbgl), with biodegradation of phenolic compounds by nitrate-reducing Azoarcus and Acidovorax strains potentially being an important process. The presence of acetogenic and sulphate-reducing bacteria only in the planktonic clone library indicates that some natural attenuation processes may occur preferentially in one of the two growth phases (attached or planktonic). Therefore, this study has provided a better understanding of the microbial ecology of this phenol-contaminated aquifer, and it highlights the need for investigating both planktonic and attached microbial communities when assessing the potential for natural attenuation in contaminated aquifers.

Congo red decolorization by immobilized laccase through chitosan nanoparticles on the glass beads

Laccase, the blue oxidase enzyme with high potency in green synthesis and biodegradation of phenolic compounds, was immobilized by means of chitosan nanoparticles (CS-NPs) on the surface of activated glass beads. Decolorization of Congo red, a harmful industrial dye, was accomplished with nanoparticulated immobilized laccase, directly attaching enzyme on the surface of the glass beads, as well as the free enzyme in order to assess the decolorization activity of immobilized and non-immobilized laccase. Glass surface functionalization was achieved by using chemicals such as sodium hydroxide, 3-aminopropyltriethoxysilane (APES), and glutaraldehyde. Dynamic light scattering (DLS) and scanning electron microscopy (SEM) were used for characterizing enzyme-associated CS-NPs, made by the ion gelation method. Fourier Transform Infrared Spectroscopy (FT-IR) was carried out to identify the attached chemical groups on the surface of the glass beads. Immobilization yields for nanoparticulated and non-nanoparticulated enzymes were 75±4.2 and 68.6±6.4%, respectively whereas, immobilization efficiency for nanoparticulated and non-nanoparticulated laccases were calculated as 40.1±3.4 and 32.2±7.5%, respectively. The applied method for immobilization resulted in increased thermal stability, reusability, and lifetime of the enzyme. Thermal stability of the nanoparticulated immobilized enzyme increased up to near boiling temperature. In addition, 98% of initial decolorization activity of the nanoparticulated immobilized enzyme was retained after 25 successive cycles.

Immobilization of tyrosinase on modified diatom biosilica: Enzymatic removal of phenolic compounds from aqueous solution

Acid and plasma treated diatom-biosilica particles, were modified with 3-aminopropyl triethoxysilane (APTES), and activated with glutaraldehyde. Then, tyrosinase was immobilized onto the pre-activated biosilica by covalent bonding. The biosilica properties were determined using SEM, and FTIR. The enzyme system has been characterized as a function of pH, temperature and substrate concentration. Optimum pH of the free and immobilized enzyme was found to be pH 7.0. Optimum temperatures of the free and immobilized enzymes were determined as 35 and 45°C respectively. The biodegradation of phenolic compounds (i.e., phenol, para-cresol and phenyl acetate) has been studied by means of immobilized tyrosinase in a batch system. The immobilized tyrosinase retained about 74% of its original activity after 10 times repeated use in the batch system. Moreover, the storage stability of the tyrosinase-biosilica system resulted excellent, since they maintained more than 67% of the initial activity after eighth week storage. Highly porous structure of biosilica can provide large surface area for immobilization of high quantity enzyme. The porous structure of the biosilica can decrease diffusion limitation both substrate phenols and their products. Finally, the immobilized tyrosinase was used in a batch system for degradation of three different phenols.

Substrate interactions and kinetics study of phenolic compounds biodegradation by Pseudomonas sp. cbp1-3

A new strain cbp1-3 was isolated from activated sludge of a coking plant in Tianjin and identified as Pseudomonas sp. based on physiological and 16S rRNA gene sequence analysis, which could completely degrade 1400mg/L phenol, 800mg/L m-cresol and 150mg/L 4-chlorophenol (4-CP) as sole carbon and energy source within 60h, 40h and 60h, respectively. Investigation on substrate interactions in the biodegradation of mixed phenols indicated that phenol and m-cresol exhibited a mutual inhibition to each other, and they (only below 300mg/L) both promoted the 4-CP biodegradation. However, 4-CP strongly inhibited the biodegradation of other phenols in their mixtures despite of the low concentration. Further analysis showed that the newly proposed kinetic model for cell growth on ternary substrates fitted the experimental data very well. And sensitivity analysis suggested that substrate interaction coefficients fi (i=12, 13 and 23) of the models were the most sensitive parameters. Finally, yield coefficient, calculated for all conditions, taken as a whole, followed an allometric decline pattern with the increase of substrate concentration.

Biological removal of p-cresol, phenol, p-hydroxybenzoate and ammonium using a nitrifying continuous-flow reactor

Phenolic compounds biodegradation and its effect on the nitrification process were studied. A continuous stirrer tank reactor was operated in four stages, and phenolic compounds were fed as sequential way. In the first stage, at loading rate of 220mgNH4+–N/Ld, the consumption efficiency was of 91%, being the product, nitrate. After that, p-cresol was fed at 53mgC/Ld, reaching removal efficiencies for both substrates higher than 90%. In the third stage, p-hydroxybenzoate was fed at 56mgC/Ld, and the removal efficiencies for all substrates remained high. In the last stage, the reactor was fed at 54mgC/Ld of phenol, and it caused a diminishing on the ammonium removal efficiency; however, all phenolic compounds were efficiently removed. Kinetic results showed that the presence of each phenolic compound improved the ammonium oxidizing activity, but the nitrite oxidizing activity was not affected.

Effect of S0/X0 ratio and acclimation on respirometry of activated sludge in the cometabolic biodegradation of phenolic compounds

Aerobic batch biodegradation experiments and respirometric analysis were performed in order to investigate the effect of S0/X0 (substrate/biomass) ratio and preliminary acclimation on bi-solute biodegradation of phenolic compounds. It was shown that 2-chlorophenol (2-CP) and 2-nitrophenol (2-NP) could be cometabolically biodegraded only with acclimated biomass in the presence of phenol as growth substrate. Acclimation resulted in domination of phenol oxidizing bacteria which could induce the necessary enzymes for cometabolic transformation of 2-CP and 2-NP. Biodegradation of the cometabolic compounds occurred even after depletion of phenol at resting cell conditions. Both compounds could be successfully biodegraded by the acclimated biomass at initial substrate concentrations as high as 300mg/L. Respirometric analysis showed that the optimum S0/X0 ratio ranged between 1.5 and 5.5mg CODeq/mg MLSS for cometabolic substrates 2-CP and 2-NP, whereas it was as high as 8.5mg CODeq/mg MLSS for phenol which corresponds to a phenol concentration of about 1500mg/L.

Immobilization of Delftia tsuruhatensis in macro-porous cellulose and biodegradation of phenolic compounds in repeated batch process

Delftia tsuruhatensis BM90, previously isolated from Tyrrhenian Sea and selected for its ability to degrade a wide array of phenolic compounds, was immobilized in chemically modified macro porous cellulose. The development of bacterial adhesion on the selected carrier was monitored by scanning electron microscopy. Evident colonization started already after 8h of incubation. After 72h, almost all the carrier surface was covered by the bacterial cells. Extracellular bacterial structures, such as pili or fimbriae, contributed to carrier colonization and cell attachment. Immobilized cells of D. tsuruhatensis were tested for their ability to biodegrade a pool of 20 phenols in repeated batch process. During the first activation batch (72h), 90% of phenols degradation was obtained already in 48h. In the subsequent batches (up to 360h), same degradation was obtained after 24h only. By contrast, free cells were slower: to obtain almost same degradation, 48h were needed. Thus, process productivity, achieved by the immobilized cells, was double than that of free cells. Specific activity was also higher suggesting that the use of immobilized D. tsuruhatensis BM90 could be considered very promising in order to obtain an efficient reusable biocatalyst for long-term treatment of phenols containing effluents.

Determination of biodegradability of phenolic compounds, characteristic to wastewater of the oil-shale chemical industry, on activated sludge by oxygen uptake measurement

The aim of this study was to investigate the biodegradation of phenol, o-cresol and p-cresol individually and as bi-substrate mixtures at low initial substrate concentrations. Activated sludge was taken from the Kohtla-Järve wastewater treatment plant, Estonia, which is also treating phenolic wastewater from the oil-shale chemical industry and is considered to be acclimated to the phenolic compounds. Respirometric data have been used for evaluation of the kinetic parameters describing the bio-oxidation of substrates. Activated sludge was able to degrade phenol and p-cresol faster than o-cresol, showing better affinity to p-cresol. However, at higher concentrations, phenol and p-cresol exhibited also an inhibitory effect to the microorganisms. The highest values for maximum rate of oxygen uptake () were obtained for the bi-substrate system of phenol–p-cresol among the mixtures containing both substrates at equal concentrations from 0.005 mM to 0.050 mM. Concerning the systems containing one substrate at 0.1 mM and the other substrate varied in the abovementioned range, the highest values were found for phenol–o-cresol(0.1 mM). The interaction parameters indicated that phenol had a stronger inhibition effect on the biodegradation of p-cresol than p-cresol had on the biodegradation of phenol. However, the obtained interaction parameters for systems of phenol–o-cresol indicated that o-cresol had a stronger inhibition effect on the biodegradation of phenol, which in turn had a mild inhibition or even enhancing effect on the biodegradation of o-cresol. In the case of a 1:1 mixture, phenol and o-cresol had a similar mild inhibition effect on each other's biodegradation.

Biodegradation of Phenolic Compounds in Creosote Treated Wood Waste by a Composting Microbial Culture Augmented with the Fungus &lt;i&gt;Thermoascus aurantiacus&lt;/i&gt;

Problem statement: Creosote is used as a wood preservative and water proof agent in railway sleepers, utility poles, buildings foundations and fences and garden furniture. It is a mixture of over 300 hydrocarbons which include 75% polycyclic aromatic hydrocarbons, 2-17% phenolic compounds and 10-18% heterocyclic organic compounds. Exposure to creosote may result in several health problems including damage to kidney, liver, eyes and skin. Potential contamination of soil and water exist from creosote treated wood from construction and demolition sites. Approach: The possibility of using an invessel composting process augmented with the ascomycetous fungus Thermoascus aurantiacus as a mesophilic/thermophilic bioremediation option for the degradation of phenolic compounds in creosote treated wood waste was evaluated. Results: The temperatures of bioremediation process reached thermophilic phase and the mesophilic and thermophilic lag phases were clearly identified. The moisture content decreased significantly indicating that the water produced by microbial respiration did not compensate for the water lost as vapor with the exhaust gases. Initial increases in pH due to the breakdown of organic nitrogen to ammonium and final drop in pH due to the formation of organic acids and the loss of ammonium with the exhaust gases in the latter stage were observed. Different degradation rates were observed in the mesophilic and thermophilic stages of composting. The control experiment achieved higher reductions of volatile solids, total carbon and TKN and higher degradation of phenolic compounds, cellulose and lignin, indicating a higher level of activity of microorganisms during the composting process compared with the inoculated experimental trial. The stability and maturity of the product of the control experiment were also better than those of the product from the inoculated experimental trial. Conclusion: The inoculation of the cellulolytic-thermophilic fungus Thermoascus aurantiacus did not accelerate the bioremediation process in degrading phenolic compounds and the fungus may have inhibited the growth and metabolic activities of composting organisms.

Enhanced anaerobic biodegradability of real coal gasification wastewater with methanol addition

Coal gasification effluent is a typical refractory industrial wastewater with a very poor anaerobic biodegradability due to its toxicity. Methanol was introduced to improve anaerobic biodegradability of real coal gasification wastewater, and the effect of methanol addition on the performance was investigated in a mesophilic upflow anaerobic sludge bed reactor with a hydraulic retention time of 24 hr. Experimental results indicated that anaerobic treatment of coal gasification wastewater was feasible with the addition of methanol. The corresponding maximum COD and phenol removal rates were 71% and 75%, respectively, with methanol concentration of 500 mg COD/L for a total organic loading rate of 3.5 kg COD/(m 3·day) and a phenol loading rate of 0.6 kg/m 3·day). The phenol removal rate was not improved with a higher methanol concentration of 1000 mg COD/L. Substrate utilization rate (SUR) tests indicated that the SURs of phenol were 106, 132, and 83 mg phenol/(g VSS·day) at methanol concentrations of 250, 500, and 1000 mg COD/L, respectively, and only 45 mg phenol/(g VSS·day) in the control reactor. The presence of methanol could reduce the toxicity of coal gasification wastewater and increase the biodegradation of phenolic compounds.

Enrichment of Phenol Degrading Moderately Halophilic Bacterial Consortium from Saline Environment

A versatile, moderately halophilic bacterial consortium was developed for the biodegradation of phenolic compounds under saline conditions. The bacterial consortium was isolated from mixtures of soil from phenol contaminated sites and as well as from areas having proximity to saline environment. The isolated moderately halophilic bacterial consortium utilized different phenolic compounds as sole source of carbon source. Phenol was utilized by the consortium at a range of salt concentrations from 10- 150 g/L NaCl where the optimum degradation was achieved at 50 g/L of NaCl. The bacterial consortium utilized up to 300 mg/L of phenol most effi ciently than the individual strains present in the consortium under saline conditions. The 16S r-RNA gene analysis and biochemical tests showed that the bacterial consortium contained six bacterial strains, which were identifi ed as Bacillus cereus, Arthrobacter sp., Bacillus licheniformis, Halomonas salina, Bacillus pumilus and Pseudomonas aeruginosa. Such moderately halophilic bacterial consortium might be useful for the treatment of industrial saline wastewater, particularly, in environments contaminated with phenolic wastes.

Modeling the biodegradation of phenolic compounds by microalgae

Phenols represent a group of organic pollutants frequently found in many near-shore marine systems. The microbial degradation of phenols, mainly by bacteria and fungi, has been extensively studied both experimentally and theoretically, but only relatively recently the capabilities of some algae for phenols biodegradation gained interest. The biodegradation of phenols by microalgae occurs only under aerobic conditions. In this paper, a dynamic energy budget model is proposed for describing aerobic biodegradation of phenolic compounds by microalgae and qualitatively validated against experimental data. A microalgal cell has the ability to produce biomass via the autotrophic assimilation (uptake of light and dissolved inorganic carbon), the heterotrophic assimilation (uptake of dissolved organic carbon) and, to a lesser extend, via the biodegradation of phenols. The rules of synthesizing units are used for the uptake and interactions of substrates and for the merging of assimilates. The model is capable of making predictions under oxygen and carbon (inorganic and organic) limiting conditions. Model predictions cover a wide range of experimental evidence, but also give a possible explanation for the inhibition of bioremoval of phenols in the presence of glucose. The dissolved oxygen profiles numerically observed show low oxygen concentration during the intermediate phase of the biodegradation process and a rapid increase after the consumption of the phenolic compound, indicating that lack of oxygen could be a limiting factor for the biodegradation of phenols. The presence of glucose increases the specific growth rate but decreases the specific biodegradation rate of the phenolic compound. Model analysis suggests that this inhibition may be due to the competition for oxygen between glucose and phenol assimilation. In general, the balance between the benefits and costs of the different types of assimilation determines the microalgal growth rates as well as the phenol biodegradation rates. Being based on general assumptions, the model can be applied to the biodegradation of a wide variety of aromatic compounds.