A large number of enzymes from bacteria, fungi, and plants have been reported to be involved in the biodegradation of toxic organic pollutants. Bioremediation is a cost effective and nature friendly biotechnology that is powered by microbial enzymes. The research activity in this area would contribute towards developing advanced bioprocess technology to reduce the toxicity of the pollutants and also to obtain novel useful substances. The information on the mechanisms of bioremediation-related enzymes such as oxido-reductases and hydrolases have been extensively studied. This review attempts to provide descriptive information on the enzymes from various microorganisms involved in the biodegradation of wide range of pollutants, applications, and suggestions required to overcome the limitations of their efficient use.

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Role of microbial enzymes in the bioremediation of pollutants: a review.

The ability of peroxidases and laccases enzymes to treat organic pollutants is reviewed. Enzymatic methods generally have low energy requirements, are easy to control, can operate over a wide range of conditions and have a minimal environmental impact. Peroxidases and laccases have broad substrate specificities and can catalyze the oxidation of a wide range of toxic organic compounds. The results show that an enzymatic oxidation can diminish the toxicity of some polycyclic aromatic hydrocarbons (PAHs), phenols, organophosphorus pesticides and azo dyes in laboratory and some field conditions. Due to the hydrophobicity and low aqueous solubility of these substrates, reactions are usually performed in the presence of organic solvents. However, it was detected that organic solvents can provoke enzyme denaturation, unfavorable substrate partition, inhibition or stabilization of enzyme–substrate complexes, depending on the enzyme, substrate and organic solvent used. Strategies to overcome these problems are proposed. Additionally, the low stability of heme-containing peroxidases to hydrogen peroxide, the low reaction rates of laccases, the mediators toxicity, the limited availability and high costs of these enzymes are other limitations detected for commercial applications. Due to field reaction conditions are more complex than laboratory conditions efforts have to be made to achieve the cheap overproduction of these biocatalysts in heterologous hosts and also their modification by chemical means or protein engineering to obtain more robust and active enzymes.

Potential use of oxidative enzymes for the detoxification of organic pollutants

Ionic Liquids: Applications and Perspectives

Purification of a new manganese peroxidase of the white-rot fungus Irpex lacteus, and degradation of polycyclic aromatic hydrocarbons by the enzyme.

Four major hemoproteins were purified by isoelectric focusing from an extracellular crude enzyme preparation, produced by the white rot fungus Phanerochaete chrysosporium under carbon-limited conditions. Both the crude enzyme and the purified proteins oxidised milled wood lignin, HCl-dioxane-extracted straw lignin and alkali straw lignin in the presence of hydrogen peroxide. The oxidation resulted mainly in further polymerisation of the lignins and was enhanced by addition of veratryl alcohol to the reaction mixture. Alkali straw lignin was also polymerised by horseradish peroxidase, although veratryl alcohol had no influence on this reaction.

Research letterPolymerisation of lignins by ligninases from Phanerochaete chrysosporium

The reaction of manganese peroxidase (MnP) of the white-rot fungusBjerkandera adusta with synthetic lignin dehydrogenation polymer, DHP) in acetone medium was investigated. Gel-permeation chromatography of the DHP treated by MnP demonstrated depolymerization of syringyl DHP in the reaction mixture containing 70% acetone; moreover, concomitant repolymerization occurred to give highly polymerized products. Guaiacyl DHP was only repolymerized by MnP in the same acetone solution without giving degradation products. Addition of ascorbic acid to reaction mixtures containing acetone resulted in preferential depolymerization of syringyl DHP.

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Reaction of manganese peroxidase of Bjerkandera adusta with synthetic lignin in acetone solution

The oxidation of lignin peroxidase (LiP) of Phanerochaete chrysosporium was examined using various phenolics and aromatic amines as substrates in organic solvents. LiP oxidized 3,3′-dimethoxybenzidine more effectively in several 70% aqueous water-miscible organic solvents including ethylene glycol and methylcellosolve than in water. LiP activity in water-miscible organic solvents was correlated with the Dimroth-Reichardt parameter ( E T (30)) of the solvents, which is directly related to free energy of the solvation process. In addition, absorption spectra of LiP in several glycols were similar to those in succinate buffer. These results suggest that these glycols do not disturb the conformation around the active center, heme, of LiP. Furthermore, LiP catalyzed the oxidation of several phenolics and aromatic amines including 3,3′-dimethoxybenzidine, o -, and p -phenylenediamines and o -aminophenol in 70% aqueous ethylene glycol solution. These substrates were shown to have low ionization potential and high hydrophobicity, and thus to be suitable substrates for the reaction of LiP in water-miscible organic solvents.

Effects of water-miscible organic solvents on the reaction of lignin peroxidase of Phanerochaete chrysosporium

Production and characterization of ligninolytic enzymes of Bjerkandera adusta grown on wood meal/wheat bran culture and production of these enzymes using a rotary-solid fermenter

The oxidation of various phenolics and aromatic amines by manganese-dependent peroxidase (MnP) of Bjerkandera adusta was examined in aqueous organic media. MnP retained its activities in several 70% (v/v) aqueous solutions of water-miscible organic solvents including ethylene glycol, diethylene glycol, acetone and acetonitrile. The absorption spectra of MnP in these aqueous organic media were similar to that observed in the reaction without solvent addition, indicating that the heme of MnP was little affected by the addition of these water-miscible organic solvents. MnP was also found to oxidize Mn(II) to Mn(III) in these 70% (v/v) aqueous organic media. The oxidation of Mn(II) by MnP was correlated with the Dimroth–Reichardt parameter, ET(30), of the solvents. Furthermore, MnP catalyzed the oxidation of anisidines, aminophenols, phenylenediamines and phenolics in aqueous 70% (v/v) acetone, acetonitrile and diethylene glycol media. Aromatic amines that have high hydrophobicity were shown to be suitable for the reaction of MnP in aqueous water-miscible organic media.

Reaction of manganese-dependent peroxidase from Bjerkandera adusta in aqueous organic media

LiP of Phanerochaete chrysosporium was chemically modified with MPSS, and acetic and benzoic acid N-hydroxysuccinimide esters to increase the activity in organic solvents. IEF demonstrated the LiP was chemically modified with these modifers. The modification of LiP was also confirmed by GFC and anion-exchange chromatography analyses. In addition, the modified LiP retained its original activity in aqueous solution. Furthermore, these modified LiPs had higher 3,3′-dimethoxybenzidine oxidation activity than the native LiP in aqueous 70% water-miscible organic solutions including ethylene glycol and diethylene glycol. However, the activities of these modified enzymes were found to be negligibly low in water-immiscible organic solvents such as benzene and toluene. Furthermore, the effects of these introducing groups and the properties of organic solvents on the reaction of LiP in water-miscible organic solvents were investigated. The reaction of LiP modified with aliphatic acid was found to depend on the visco...

Shinichi Yoshida

Papers

Reaction of manganese peroxidase of Bjerkandera adusta with synthetic lignin in acetone solution

Effects of water-miscible organic solvents on the reaction of lignin peroxidase of Phanerochaete chrysosporium

Production and characterization of ligninolytic enzymes of Bjerkandera adusta grown on wood meal/wheat bran culture and production of these enzymes using a rotary-solid fermenter

Reaction of manganese-dependent peroxidase from Bjerkandera adusta in aqueous organic media

Reaction of Chemically Modified Lignin Peroxidase of Phanerochaete chrysosporium in Water-miscible Organic Solvents