Keith E. Taylor

Removal of phenolic compounds from synthetic wastewater using soybean peroxidase

Abstract Experiments were conducted to investigate the efficiency of using soybean peroxidase (SBP) to remove several different phenolic compounds from unbuffered synthetic wastewater. The phenol derivatives studied included parent phenol, chlorinated phenols, cresols, 2,4-dichlorophenol and 4,4′-isopropylidenediphenol (commonly known as bisphenol A). Optimum conditions to achieve at least 95% removal of these compounds were determined for the following parameters: pH, SBP dose in the absence and presence of polyethylene glycol (PEG), hydrogen peroxide to substrate ratio, and PEG dose. Experimental results showed that SBP efficiently removed aromatic compounds from synthetic wastewater in the presence of hydrogen peroxide. An increase in the hydrogen peroxide to substrate ratio beyond the optimum resulted in enzyme inactivation in all cases except for bisphenol A. The optimum pH for different phenolic compounds ranged from 5.5 to 8. For each substrate, the optimum enzyme dose in the presence of PEG varied significantly. The studies showed that PEG only slightly reduced the amount of SBP required for 95% removal of the substrate. For most of the substrates, an increase in PEG dose beyond the optimum dose did not significantly change the removal efficiency.

A model for the Protective Effect of Additives on the Activity of Horseradish Peroxidase in the Removal of Phenol

Horseradish peroxidase has been proven effective in removing phenolic compounds in wastewater and additives such as polyethylene glycol have been found very effective in reducing the minimum enzyme dose required. The effect of additives on horseradish peroxidase-catalyzed removal of phenol was investigated in this study. In the absence of additive, active enzyme is predominantly inactivated by the polymer product formed during the reaction. The specific activity of horseradish peroxidase is higher due to the presence of additive. Experiments suggest that additives combine with the polymerization products formed during the reaction, because additives have a higher partition affinity with the polymer products than peroxidases. Most of the polymer product is coupled with additive so that less enzyme interacts with the polymer product. Horseradish peroxidase still combines with polymer products and becomes inactivated but at a much slower rate when additives are present. Consequently, the enzyme activity is protected by the additives.

Comparison of additives in the removal of phenolic compounds by peroxidase-catalyzed polymerization

Several additives, polyethylene glycol, gelatin and some polyelectrolytes, were studied to compare their behaviour in the removal of phenolic compounds from aqueous solution by horseradish-peroxidase-catalyzed polymerization. The effects of additives on optimum pH range, horseradish-peroxidase saving, reaction stoichiometry and minimum additive requirements were investigated. The fate of additive after reaction was also studied. The experimental results showed that all tested additives significantly reduced the horseradish-peroxidase requirement. Comparison among them revealed that polyethylene glycol was the best choice from all perspectives. It saved more peroxidase and had no negative overdose effect shown by gelatin and polyelectrolytes. At minimum polyethylene glycol dose, there was little polyethylene glycol remaining in solution after completion of reaction. However, a considerable amount of gelatin remained in solution even at the minimum gelatin dose. Also, gelatin produced more precipitate than polyethylene glycol.

A new peroxidase color reaction: Oxidative coupling of 3-methyl-2-benzothiazolinone hydrazone (MBTH) with its formaldehyde azine. Application to glucose and choline oxidases

Hydrogen peroxide in the presence of horseradish peroxidase effects the oxidative coupling of 3-methyl-2-benzothiazolinone hydrazone with its formaldehyde azine to form a tetraazapentamethine dye. The blue chromophore, when formed at pH 3.5 and quenched with acetone or 1 N hydrochloric acid, has an extinction coefficient of 69 +/- 2 or 55 +/- 2 mM-1 cm-1, respectively. This chromogen system has been adapted for enzymatic determinations of hydrogen peroxide and of glucose in the 10- to 45-nmol range and of choline in the 5- to 20-nmol range.

A Short Review of Techniques for Phenol Removal from Wastewater

Phenolic compounds are priority pollutants with high toxicity even at low concentrations. In this review, the efficiency of both conventional and advanced treatment methods is discussed. The applicability of these treatments with phenol and some common derivatives is compared. Conventional treatments such as distillation, absorption, extraction, chemical oxidation, and electrochemical oxidation show high efficiencies with various phenolic compounds, while advanced treatments such as Fenton processes, ozonation, wet air oxidation, and photochemical treatment use less chemicals compared to the conventional ones but have high energy costs. Compared to physico-chemical treatment, biological treatment is environmentally friendly and energy saving, but it cannot treat high concentration pollutants. Enzymatic treatment has proven to be the best way to treat various phenolic compounds under mild conditions with different enzymes such as peroxidases, laccases, and tyrosinases. This review covers papers from 2013 through January 2016.

Immobilized enzyme catalyzed removal of 4-chlorophenol from aqueous solution

Abstract The ability of horseradish peroxidase enzyme attached on three different reactor matrices: cellulose filter paper, nylon balls and nylon tubing, to remove 4-chlorophenol from aqueous solution is evaluated. The enzymatic reaction is extremely fast and the reaction products remained on the reactor matrix. Detachment or release of the reaction products from the reactor matrix is not observed. Results indicate that, over 80% removal efficiency can be obtained as long as enzyme activity is not limiting in the reactor. Systematic recycle batch reactor studies reveal that, initial reaction rates exhibit saturation with substrate concentration under conditions of excess peroxide. Inactivation of enzyme active sites by reaction intermediates is observed in the reactor studies. Immobilized peroxidase also catalyzes the oxidation of other chlorophenols and cresols.

Optimization of phenol removal by a fungal peroxidase from Coprinus macrorhizus using batch, continuous, and discontinuous semibatch reactors

Abstract The use of a peroxidase from the fungus Coprinus macrorhizus for the removal of toxic organics from synthetic wastewater is explored in this study. Removal of phenols demonstrated a dependence of enzyme lifetime on enzyme concentration in batch reactors. Maximum removal of phenol under optimal conditions in a batch reactor at enzyme activity above 0.3 U ml −1 and up to 1.2 U ml −1 was 53% in the present study. Continuous addition of C. macrorhizus peroxidase (CMP) to the reactor over periods varying from 0.5 to 3 h did not improve the removal. Similarly, continuous addition of H 2 O 2 did not improve the removal of phenol. A colorimetric assay for H 2 O 2 indicated its depletion in the batch reactors. H 2 O 2 : phenol stoichiometry was greater than one if all the H 2 O 2 was added at the beginning of the reaction. Instability of the H 2 O 2 and possible decomposition by contaminating catalase in the sample preparation are two possibilities for its depletion. To overcome this depletion in the reactors regardless of the enzyme concentration, discontinuous addition of either CMP or H 2 O 2 or both was adopted. Significant improvement in phenol removal (90%) was obtained when either H 2 O 2 or CMP was added in three discrete aliquots over 0.5 h. With discontinuous addition of both reactants, the amount of CMP could be reduced to 0.3 U ml −1 while achieving 91% removal of phenol at equimolar concentration of H 2 O 2 . Thus, discontinuous addition of the reactant(s) increased the turnovers obtained by CMP and conserved the 1 : 1 phenol to peroxide stoichiometry in the clearance reaction. Spectral observation of the CMP utilized in this study showed the presence of a contaminating cyanide-like complex of the enzyme, as was observed by another group using a similar microbial peroxidase.

A procedure for the direct determination of micromolar quantities of lecithin employing enzymes as reagents

Abstract A procedure has been proposed for the determination of micromolar concentrations of lecithin. This procedure, which utilizes enzymes as reagents, is relatively quick, simple, and inexpensive, and involves no extractions. Clinical studies of the applicability of this procedure for the determination of lecithin concentrations in amniotic fluid have, as yet, not been concluded. The synthesis of sodium 2-hydroxy-3, 5-dichlorobenzenesulfonate was described. This material in purified form has proven to be very convenient for routine use in a peroxidase-catalyzed coupling to 4-aminoantipyrine.

Laccase-catalyzed removal of 2,4-dimethylphenol from synthetic wastewater: Effect of polyethylene glycol and dissolved oxygen

The potential use of laccase (SP-504) in an advanced oxidation-based treatment technology to remove 2,4-dimethylphenol (DMP) from water was investigated with and without the additive, polyethylene glycol (PEG). The DMP concentration was varied between 1.0 and 5.0 mM. The optimization of pH and enzyme concentration in the presence and absence of PEG was carried out. All experiments were carried out in continuously stirred reactors for 3h at room temperature. The reaction was initiated by adding enzyme to the reaction mixture. For more than 95% removal of DMP, the presence of PEG reduced the inactivation of enzyme so that the required enzyme concentrations were reduced by about 2-fold compared to the same reactions in the absence of PEG. Finally, the PEG concentrations were optimized to obtain the minimum dose required. For higher substrate concentrations, the availability of oxygen was insufficient in achieving 95% or more removal. Therefore, the effect of increasing dissolved oxygen at higher substrate concentration was investigated. The laccase studied was capable of efficiently removing DMP at very low enzyme concentrations and hence shows great potential for cost-effective industrial applications.

The determination of lecithin and total choline-containing phospholipids in amniotic fluid employing enzymes as reagents

Abstract Two assays which employ enzymes as reagents have been described for the determination of lecithin and TCCP in amniotic fluid. Both of these assays are relatively quick, simple, inexpensive, precise, involve no extractions, and are amenable to automation. Hemoglobin, blood cell membranes, and bilirubin, common interferences in L S ratio determinations, have been studied. Their effects on these two assays appear to be negligible. It can be inferred from preliminary studies that the described assays correlate well with each other, and with the clinical status of the fetus. The values obtained for lecithin and TCCP cmncentrations are in the same range as previous reports employing different procedures.