Peroxidative phenol removal from aqueous solutions using activated peroxidase biocatalyst

Nutrients' behavior and removal in an activated sludge system receiving Olive Mill Wastewater

This work aims to monitor inorganic nutrients (phosphorus and ammonium) behavior during the injection of Olive Mill Wastewater (OMWW) in an activated sludge process. The system was fed firstly with urban wastewater (UWW) and was alimented after its stabilization with OMWW (at 0.1% (v/v) and 1%) for 100 days. Total polyphenols, chemical oxygen demand (COD_T), nutrients, and biomass behavior against OMWW injection were investigated. The results showed a satisfactory biomass growth of 7.12 g_MLVSS.L^-1 and a high microbial activity of 21.88 mg O₂.g_MLVSS^-1.h^-1. An overall removal reached 90%, 92%, 59% and 93% respectively for, COD_T, total polyphenols, PO₄^3- and NH₄⁺. Adding OMWW at 1% seems to improve the nutrients elimination, especially phosphorus by the biological process probably though bringing more biodegradable organics. The chemical processes (precipitation/complexation) could also be involved in phosphorus removal, due to the OMWW wealth on salts elements such as calcium.

Tobacco hairy root's peroxidases are rhythmically controlled by phenol exposure

Plants like almost all living organisms, have developed a biological clock or circadian clock (CC) capable of synchronizing and adjusting various metabolic and physiological processes at certain times of the day and in a period of 24 h. This endogenous timekeeping is able to predict the environmental changes providing adaptive advantages against stressful conditions. Therefore, the aim of this work was to analyze the possible link between metabolism of xenobiotic compounds (MXC) and the CC. Synchronized Nicotiana tabacum hairy roots (HRs) were used as a validated plant model system, and peroxidases (PODs), key enzymes of the phase I in the MCX, were evaluated after phenol treatment. Two POD genes were selected and their temporal expression profiles as well as the total POD activity were analyzed in order to find circadian oscillations either under control conditions or phenol treatment. It was demonstrated that these PODs genes showed oscillatory profiles with an ultradian period (period length shorter than the circadian period), and preserving the same phases and expression peaks still under phenol treatment. The total PODs activity showed also a marked oscillatory behavior mainly in phenol-treated HRs with the highest levels at ZT23. Untreated HRs showed decrease and increase in the intensity of some basic isoforms at light and dark phase, respectively, while in phenol- treated HRs, an increase in the intensity of almost all isoforms was observed, mainly during the dark phase, being coincident with the high PODs activity detected at ZT23. The periodic analysis determined an ultradian period either in total POD activity or in the POD activity of isoform VI, being 18.7 and 15.3 h, respectively. Curiously, in phenol treated HRs, the period length of total POD activity was longer than in untreated HRs, suggesting that phenol could induce a marked oscillatory behavior in the POD activity with better performance during the dark phase, which explain the higher phenol removal efficiencies at ZT23. These findings showed novel information about the performance of PODs, which would be rhythmically controlled at biochemical level, by phenol exposure.

Effect of polyphenols on activated sludge biomass during the treatment of highly diluted olive mill wastewaters: biomass dynamics and purifying performances

This study aims to investigate the feasibility of treating olive mill waste water (OMWW) by activated sludge pilot (AS) after its high dilution (1%) by urban waste water (UWW) and to study the effect of polyphenol compounds on the biomass during the treatment. Specific oxygen uptake rate (SOUR), mixed liquor volatile suspended solids (MLVSS), chemical oxygen demand (COD) and total polyphenols, were followed up over 100 days. In spite of the polyphenols' high concentration (up to 128 mg·L^-1), successful biomass growth of 7.12 g _MLVSS.L ^-1 and activity were achieved. Most of the bacteria (Pseudomonas sp., Klebsiella oxytoca, Citrobacter fereundii, Escherichia coli and Staphylococcus sp.) and fungi (Trichoderma sp., Rhizopus sp., Aspergillus niger, Penicillium sp., Fusarium sp., Alternaria) identified in the aerobic basin during the stabilization stage were known to be resistant to OMWW and showed effective adaptation of the biomass to polyphenols in high concentration. COD and polyphenols were highly eliminated (90%, 92% respectively). The sludge volume index in the pilot settling tank was almost constant at around 120 mL.g ^-1. This suggests the possibility of managing OMWW by simple injection at a given percentage in already functioning conventional AS treating UWW.

Key process parameters involved in the treatment of olive mill wastewater by membrane bioreactor

The Olive Mill Wastewater (OMWW) biodegradation in an external ceramic membrane bioreactor (MBR) was investigated with a starting acclimation step with a Ultrafiltration (UF) membrane (150 kDa) and no sludge discharge in order to develop a specific biomass adapted to OMWW biodegradation. After acclimation step, UF was replaced by an Microfiltration (MF) membrane (0.1 µm). Sludge Retention Time (SRT) was set around 25 days and Food to Microorganisms ratio (F/M) was fixed at 0.2 kg_COD kg_MLVSS^-1 d^-1. At stable state, removal of the main phenolic compounds (hydroxytyrosol and tyrosol) and Chemical Oxygen Demand (COD) were successfully reached (95% both). Considered as a predominant fouling factor, but never quantified in MBR treated OMWW, Soluble Microbial Products (SMP) proteins, polysaccharides and humic substances concentrations were determined (80, 110 and 360 mg L^-1 respectively). At the same time, fouling was easily managed due to favourable hydraulic conditions of external ceramic MBR. Therefore, OMWW could be efficiently and durably treated by an MF MBR process under adapted operating parameters.

4-Chlorophenol biodegradation facilitator composed of recombinant multi-biocatalysts immobilized onto montmorillonite

A biodegradation facilitator which catalyzes the initial steps of 4-chlorophenol (4-CP) oxidation was prepared by immobilizing multiple enzymes (monooxygenase, CphC-I and dioxygenase, CphA-I) onto a natural inorganic support. The enzymes were obtained via overexpression and purification after cloning the corresponding genes (cphC-I and cphA-I) from Arthrobacter chlorophenolicus A6. Then, the recombinant CphC-I was immobilized onto fulvic acid-activated montmorillonite. The immobilization yield was 60%, and the high enzyme activity (82.6%) was retained after immobilization. Kinetic analysis indicated that the Michaelis-Menten model parameters for the immobilized CphC-I were similar to those for the free enzyme. The enzyme stability was markedly enhanced after immobilization. The immobilized enzyme exhibited a high level of activity even after repetitive use (84.7%) and powdering (65.8%). 4-CP was sequentially oxidized by a multiple enzyme complex, comprising the immobilized CphC-I and CphA-I, via the hydroquinone pathway: oxidative transformation of 4-CP to hydroxyquinol followed by ring fission of hydroxyquinol.

Isolation and characterization of phenol degrading bacterium strain Bacillus thuringiensis J20 from olive waste in Palestine

This study aimed at isolation of phenol degrading bacteria from olive mill wastes in Palestine. The efficiency of phenol removal and factors affecting phenol degradation were investigated. A bacterial strain (J20) was isolated from solid olive mill waste and identified as Bacillus thuringiensis based on standard morphological, biochemical characteristics and 16SrRNA sequence analysis. The strain was able to grow in a phenol concentration of 700 mg/L as the sole carbon and energy source. The culture conditions showed a significant impact on the ability of these cells to remove phenol. This strain exhibited optimum phenol degradation performance at pH 6.57 and 30 °C . Under the optimized conditions, this strain could degrade 88.6% of phenol (700 mg/L) within 96 h when the initial cell density was OD₆₀₀ 0.2. However, the degradation efficiency could be improved from about 88% to nearly 99% by increasing the cell density. Immobilization of J20 was carried out using 4% sodium alginate. Phenol degradation efficiency of the immobilized cells of J20 was higher than that of the free cells, 100% versus 88.6% of 700 mg/L of phenol in 120 h, indicating the improved tolerance of the immobilized cells toward phenol toxicity. The J20 was used in detoxifying crude OMWW, phenolic compounds levels were reduced by 61% compared to untreated OMWW after five days of treatment. Hence, B. thuringiensis-J20 can be effectively used for bioremediation of phenol-contaminated sites in Palestine. These findings may lead to new biotechnological applications for the degradation of phenol, related to olive oil production.

A new combined green method for 2-Chlorophenol removal using cross-linked Brassica rapa peroxidase in silicone oil

This study proposes a new technique to treat waste air containing 2-Chlorophenol (2-CP), namely an integrated process coupling absorption of the compound in an organic liquid phase and its enzymatic degradation. Silicone oil (47V20) was used as an organic absorbent to allow the volatile organic compound (VOC) transfer from the gas phase to the liquid phase followed by its degradation by means of Cross-linked Brassica rapa peroxidase (BRP) contained in the organic phase. An evaluation of silicone oil (47V20) absorption capacity towards 2-CP was first accomplished by determining its partition coefficient (H) in this solvent. The air-oil partition coefficient of 2-CP was found equal to 0.136 Pa m(3) mol(-1), which is five times lower than the air-water value (0.619 Pam(3) mol(-1)). The absorbed 2-CP was then subject to enzymatic degradation by cross-linked BRP aggregates (BRP-CLEAs). The degradation step was affected by four parameters (contact time; 2-CP, hydrogen peroxide and enzyme concentrations), which were optimized in order to obtain the highest conversion yield. A maximal conversion yield of 69% and a rate of 1.58 mg L(-1) min(-1)were obtained for 100 min duration time when 2-CP and hydrogen peroxide concentrations were respectively 80 mg L(-1) and 6 mM in the presence of 2.66 UI mL(-1) BRP-CLEAs. The reusability of BRP-CLEAs in silicone oil was assessed, showing promising results since 59% of their initial efficiency remained after three batches.

Electrocoagulation treatment of black liquor from soda-AQ pulping of wheat straw

The effect of electrocoagulation treatment was investigated on black liquor from soda-anthraquinone (AQ) pulping of wheat straw. Removal of phenol, chemical oxygen demand (COD), color, total suspended solids (TSS), total dissolved solids (TDS), and total solids (TS) from black liquor was investigated at different current densities by using aluminum electrodes at various electrolysis times (10, 25, 40, 55, and 70 min) and pH levels (3, 5, 7, 9, and 10.5). It was observed that at 16 V, electrolysis time of 55 min and current density of 61.8 mA/cm(2) were sufficient for the removal of the pollutants. Energy consumption was evaluated as an important cost-relation parameter. Results showed that the electrocoagulation treatment reduced color intensity from the high initial value of 18,750 to 220 PCU. This was strongly influenced by the pH level of the wastewater. In addition, it was found that the removal efficiency increased with increasing of current density. The maximum efficiencies for removal were 98.8, 81, 80, 92, 61, and 68 % for color, phenol, COD, TSS, TDS, and TS, respectively. The lowest energy consumption values were obtained at neutral pH after 55 min. Electrocoagulation was found to be an effective, simple, and low-cost technique to treat black liquor.

Removal of Phenol by A. belladonna L. Hairy Root

Phenolic compounds that present in the several industries are harmful and dangerous for human health. In this study we have studied the potential of Atropa belladonna hairy roots in phenol removal of wastewater. The optimal conditions for the removal process were evaluated using different phenol (10-500 mg.1(-1)) and H2O2 (1-15 Mm) concentrations. In the presence of H2O2, Roots were able to remove phenol concentrations up to 500 mg.1(-1). in the wide range of pH (4-9), reaching high removal efficiency. When roots were re-used for five consecutive cycles, phenol removal efficiency decreased from 98-62%, in the last cycle. After the removal process, the solutions were obtained from the experiment were estimated for their toxicity using a test with Lactaca sativa L. seeds. Results showed that the treated solution was less toxic than the parent solution.

Use of hairy roots extracts for 2,4-DCP removal and toxicity evaluation by Lactuca sativa test

2,4-Dichlorophenol (2,4-DCP) is widely distributed in wastewaters discharged from several industries, and it is considered as a priority pollutant due to its high toxicity. In this study, the use of different peroxidase extracts for 2,4-DCP removal from aqueous solutions was investigated. Tobacco hairy roots (HRs), wild-type (WT), and double-transgenic (DT) for tomato basic peroxidases (TPX1 and TPX2) were used to obtain different peroxidase extracts: total peroxidases (TPx), soluble peroxidases (SPx), and peroxidases ionically bound to the cell wall (IBPx). All extracts derived from DT HRs exhibited higher peroxidase activity than those obtained from WT HRs. TPx and IBPx DT extracts showed the highest catalytic efficiency values. The optimal conditions for 2,4-DCP oxidation were pH 6.5, H2O2 0.5 mM, and 200 U mL(-1) of enzyme, for all extracts analyzed. Although both TPx extracts were able to oxidize different 2,4-DCP concentrations, the removal efficiency was higher for TPx DT. Polyethylene glycol addition slightly improved 2,4-DCP removal efficiency, and it showed some protective effect on TPx WT after 2,4-DCP oxidation. In addition, using Lactuca sativa test, a reduction of the toxicity of post removal solutions was observed, for both TPx extracts. The results demonstrate that TPx extracts from both tobacco HRs appear to be promising candidate for future applications in removing 2,4-DCP from wastewaters. This is particularly true considering that these peroxidase sources are associated with low costs and are readily available. However, TPx DT has increased peroxidase activity, catalytic efficiency, and higher removal efficiency than TPx WT, probably due to the expression of TPX1 and TPX2 isoenzymes.

Effective biochemical decomposition of chlorinated aromatic hydrocarbons with a biocatalyst immobilized on a natural enzyme support

The enzymatic decomposition of 4-chlorophenol metabolites using an immobilized biocatalyst was investigated in this study. Catechol 1,2-dioxygenase for ortho ring cleavage obtained via cloning of the corresponding gene cphA-I from Arthrobacter chlorophenolicus A6 was overexpressed and purified. It was found that the cphA-I enzyme could catalyze the degradation of catechol, 4-chlorocatechol, and 3-methylcatechol. The expressed enzyme was immobilized onto a natural enzyme support, fulvic acid-activated montmorillonite. The immobilization yield was as high as 63%, and the immobilized enzyme maintained high substrate utilization activity, with only a 15-24% reduction in the specific activity. Kinetic analysis demonstrated marginal differences in νmax and KM values for the free and immobilized enzymes, indicating that inactivation of the immobilized enzyme was minimal. The immobilized enzyme exhibited notably increased stability against changes in the surrounding environment (temperature, pH, and ionic strength). Our results provide useful information for the effective enzymatic biochemical treatment of hazardous organic compounds.

Antioxidant response of tobacco (Nicotiana tabacum) hairy roots after phenol treatment

Phenol is released to the environment from a wide variety of industrial effluents and it causes severe problems to human health and ecosystem. In the present study, we determined that Nicotiana tabacum hairy roots (HRs) double transgenic (DT) for two peroxidase genes (tpx1 and tpx2) showed higher phenol removal efficiency than wild type (WT) HRs after 120 h of phenol treatment at the expense of endogenous H(2)O(2). Besides, to determine whether phenol could induce oxidative stress on tobacco HRs, we analyzed the antioxidant response, superoxide anion (O(2)(-)) localization and malondialdehyde (MDA) levels. Both HRs treated with phenol, showed significant increases in peroxidase (PX) activity mainly at the end of the assay (120 h) being PX activity from transgenic HRs 40% higher than that of WT HRs. Superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities showed significant increases from 24 to 120 h of phenol treatment. PX, SOD and APX isoforms were also analyzed and slight changes were observed only in PX patterns. Both HRs showed significant differences in total glutathione (TGSH) content during treatment, being higher in DT HRs than in WT HRs. At the end of the assay, a greater accumulation of O(2)(-) in different root zones was observed in WT and DT HRs. Moreover, phenol was able to increase the MDA levels in WT HRs from 48 to 120 h of the treatment, but no significant changes were observed in DT HRs. Results suggest that under these experimental conditions, DT HRs would be more tolerant to phenol than WT HRs.

Phenol tolerance, changes of antioxidative enzymes and cellular damage in transgenic tobacco hairy roots colonized by arbuscular mycorrhizal fungi

Phytoremediation has been recognized as a cheap and eco-friendly technology which could be used for the remediation of organic pollutants, such as phenolic compounds. Besides, the extent to which plants react to environmental pollution might depend on rhizosphere processes such as mycorrhizal symbiosis. In the present work, phenol tolerance of transgenic tobacco hairy roots (HR), namely TPX1, colonized with an arbuscular mycorrhizal fungus (AMF) was studied. However, the question is whether AMF symbiosis can moderate adverse effects of phenol to the plant tissues. Thus, the antioxidative response as well as parameters of oxidative damage, like malondialdehyde (MDA) content, were determined. Antioxidative enzymes such as peroxidase, superoxide dismutase, ascorbate peroxidase were higher in TPX1 HR colonized with AMF, compared to wild type HR colonized by AMF, in the presence of increasing concentrations of the pollutant. Besides, MDA levels remained unaltered in TPX1 HR associated with AMF treated with the xenobiotic. These results, suggested that this culture could tolerate phenol and moreover, it has an efficient protective mechanism against phenol-induced oxidative damage, which is of great importance in the selection of species with remediation capacities. Thus, transgenic HR colonized with AMF could be considered as an interesting model system to study different processes which play a key role in the phytoremediation of organic pollutants.

Electrochemical removal of phenol from oil refinery wastewater

This study explores the possibility of using electrocoagulation to remove phenol from oil refinery waste effluent using a cell with horizontally oriented aluminum cathode and a horizontal aluminum screen anode. The removal of phenol was investigated in terms of various parameters namely: pH, operating time, current density, initial phenol concentration and addition of NaCl. Removal of phenol during electrocoagulation was due to combined effect of sweep coagulation and adsorption. The results showed that, at high current density and solution pH 7, remarkable removal of 97% of phenol after 2h can be achieved. The rate of electrocoagulation was observed to increase as the phenol concentration decreases; the maximum removal rate was attained at 30 mg L(-1) phenol concentration. For a given current density using an array of closely packed Al screens as anode was found to be more effective than single screen anode, the percentage phenol removal was found to increase with increasing the number of screens per array. After 2h of electrocoagulation, 94.5% of initial phenol concentration was removed from the petroleum refinery wastewater. Energy consumption and aluminum Electrode consumption were calculated per gram of phenol removed. The present study shows that, electrocoagulation of phenol using aluminum electrodes is a promising process.

Technologies for the removal of phenol from fluid streams: a short review of recent developments

The available technologies for the abatement of phenol from water and gaseous streams are briefly reviewed, and the recent advancements summarized. Separation technologies such as distillation, liquid-liquid extraction with different solvents, adsorption over activated carbons and polymeric and inorganic adsorbents, membrane pervaporation and membrane-solvent extraction, have been discussed. Destruction technologies such as non-catalytic, supercritical and catalytic wet air oxidation, ozonation, non-catalytic, catalytic and enzymatic peroxide wet oxidation, electrochemical and photocatalytic oxidation, supercritical wet gasification, destruction with electron discharges as well as biochemical treatments have been considered. As for the abatement of phenol from gases, condensation, absorption in liquids, adsorption on solids, membrane separation, thermal, catalytic, photocatalytic and biological oxidation have also been considered. The experimental conditions and the performances of the different techniques have been compared.

Application of Brassica napus hairy root cultures for phenol removal from aqueous solutions

Phenolic compounds present in the drainage from several industries are harmful pollutants and represent a potential danger to human health. In this work we have studied the removal of phenol from water using Brassica napus hairy roots as a source of enzymes, such as peroxidases, which were able to oxidise phenol. These hairy roots were investigated for their tolerance to highly toxic concentrations of phenol and for the involvement of their peroxidase isoenzymes in the removal of phenol. Roots grew normally in medium containing phenol in concentrations not exceeding 100 mg l(-1), without the addition of H(2)O(2). However, roots were able to remove phenol concentrations up to 500 mg l(-1), in the presence of H(2)O(2), reaching high removal efficiency, within 1h of treatment and over a wide range of pH (4-9). Hairy roots could be re-used, at least, for three to four consecutive cycles. Peroxidase activity gradually decreased to approximately 20% of the control, at the fifth cycle. Basic and near neutral isoenzymes (BNP) decreased along time of recycling while acidic isoenzymes (AP) remained without changes. Although both group of isoenzymes would be involved in phenol removal, AP showed higher affinity and catalytic efficiency for phenol as substrate than BNP. In addition, AP retained more activity than BNP after phenol treatment. Thus, AP appears to be a promising isoenzyme for phenol removal and for application in continuous treatments. Furthermore, enzyme isolation might not be necessary and the entire hairy roots, might constitute less expensive enzymatic systems for decontamination processes.