Influence of position of substituent groups on removal of chlorophenols and cresols by horseradish peroxidase and determination of optimum conditions.
ABSTRACT Enzymatic treatment of o-, m-, and p-chlorophenols and o-, m-, and p-cresols from artificial wastewater was undertaken through the enzymatic conversion into the corresponding phenoxy radicals with horseradish peroxidase (HRP) and nonenzymatic radical coupling reaction. The concentration of chlorophenols and cresols decreased sharply over the reaction time and water-insoluble oligomer precipitates were generated. The optimum conditions were determined to be the H2O2 concentration of 2.5 mM and poly(ethylene glycol) with molecular mass of 1.0 x 10(4) (10K-PEG) of 0.10 mg/cm3 at 30 degrees C for treatment of p-chlorophenol at 2.5 mM. The optimum pH values depended on the relative position of a chlorine atom for chlorophenols and on a methyl group for cresols. Concentrations of HRP and 10K-PEG were increased to 1.0 U/cm3 and 1.0 mg/cm3 respectively to treat m-chlorophenol highly. For o-chlorophenol, a decrease in the pH value to 3.0 after the enzymatic treatment led to the enhancement of the aggregation of oligomer precipitates. The % residual value for o-cresol effectively decreased by absorbing water-soluble intermediates on the chitosan films. These results indicate that chlorophenols and cresols were removed to a great degree by this technique, although the detailed procedure depended on the position of substituent groups of chlorophenols and cresols.
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ABSTRACT: Olive mill waste water (OMWW) originating from a two-phase olive oil-producing plant was treated with a crude peroxidase extract prepared from onion solid by-products. The treatments were based on a 3×3 factorial design, employing a series of combinations of pH and H2O2, in order to identify optimal operational conditions. The treatment performance was assessed by estimating the removal percentage of total polyphenols. The model established produced a satisfactory fitting of the data (R 2=0.94, p=0.0158), while the second-order polynomial equation used to describe the process indicated that peroxidase-catalysed polyphenol removal in diluted OMWW is facilitated at relatively low pH and intermediate H2O2 values. A predicted value of 50.7±9.5% removal was calculated under optimal operational conditions (pH 2.76, [H2O2]=3.56mM). Analysis of an untreated and an optimally treated sample by high performance liquid chromatography revealed that enzyme treatment brought about alteration in the original OMWW polyphenolic profile. The use of peroxidase from onion solid by-products is proposed as an alternative means that could have a prospect in bioremediation applications. KeywordsBiocatalysis-Bioremediation-Olive mill waste water-Onion-Peroxidase-PolyphenolsEnvironmental Chemistry Letters 01/2010; 8(3):271-275. DOI:10.1007/s10311-009-0216-z · 1.91 Impact Factor
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ABSTRACT: Alkylphenols were effectively treated with horseradish peroxidase at pH 7.0 and 30 degrees C in the presence of H(2)O(2) and poly(ethylene glycol) irrespective of the relative position or isomeric form of the alkyl chains. Water-insoluble oligomer precipitates were readily filtered out after enzymatic treatment, and transparent and colorless solutions were obtained for all p- and m-alkylphenols used.Bioscience Biotechnology and Biochemistry 06/2008; 72(5):1368-71. DOI:10.1271/bbb.70784 · 1.21 Impact Factor
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ABSTRACT: A very large amount of phenol-polluted waters are formed from the production of olive oil (olive mill waste water, OMWW), and the main problem associated with their disposal is a viable means of effective treatment. Biochemical processes used for treating OMWW are generally considered to be of high capital and operating costs with limited efficiency. This is mainly due to particularly high levels of phenolic compounds, which are considered major contributors to the toxicity and antibacterial activity of OMWW, and limit their microbial treatment and/or use as fertilizers. Although the use of bacterial and fungal enzymes has gained interest in studies pertaining to bioremediation applications, plant enzymes have been given less attention or even disregarded. In this view, this study aimed at investigating the use of a crude peroxidase preparation from onion solid by-products for oxidising hydrocaffeic acid, a typical o-diphenol with a structure very similar to various phenolic derivatives that may occur in OMWW. Increased enzyme activity was observed at a pH value of 4, but considerable activity was also retained for pH upto 7. Favourable temperatures for increased activity varied between 30 and 50°C, 40°C being the optimal. Liquid chromatography–mass spectrometry analysis of a homogenate/H2O2-treated hydrocaffeic acid solution revealed the existence of three major oxidation products, which were identified as dehydrodimers. Based on the data generated, a putative pathway for the formation of the peroxidase-mediated hydrocaffeic dehydrodimers was proposed.European Food Research and Technology 08/2008; 227(5):1379-1386. DOI:10.1007/s00217-008-0854-6 · 1.39 Impact Factor