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Biocatalytic Upgrading of Opportunity Crudes
Published in Wael Ahmed Ismail, Jonathan Van Hamme, Hydrocarbon Biotechnology, 2023
The work previously discussed in the context of enzymatic conversion of PAH using chloroperoxidase and the handicap of chlorine incorporation in the product, also reported the removal of 53% of the Ni and 27% of the V present in crude oil (Mogollon et al., 1998). In this case, when porphyrins were used as model compounds, the BDM of nickel octaethylporphine and vanadium octaethylporphine was studied using a ternary solvent system containing toluene, isopropanol, and an aqueous buffer of pH of 3.0, which was required to dissolve the petroporphyrin molecules. In addition to the model compounds, an asphaltene fraction from Cold lake heavy oil was also studied. The reported BDM for the model compounds was much higher than that observed for the asphaltene fraction. In fact, it was 93% for nickel octaethylporphine, 53% for vanadium octaethylporphyrin but only 20% for the asphaltene fraction. It is important to emphasize once more that besides its feebleness, the chloroperoxidase enzyme presents the inconvenience of needing the concerted action of hydrogen peroxide and chloride. The potential production of chlorinated organic molecules represents an additional drawback for this enzymatic system. In fact, besides its high peroxidase activity and its versatility, chloroperoxidases are well known as biocatalysts for the halogenation of aromatic molecules, as in the case of PAHs will be an undesirable reaction of the aromatic core of the metal-bearing compounds (Ayala et al., 2000; Vâzquez-Duhalt et al., 2001).
Halogenases with Potential Applications for the Synthesis of Halogenated Pharmaceuticals
Published in Peter Grunwald, Pharmaceutical Biocatalysis, 2019
Georgette Rebollar-Pérez, Cynthia Romero-Guido, Antonino Baez, Eduardo Torres
The first halogenating enzyme to be identified was the chloroperoxidase (Fe(III)-heme CPO) from the fungus Caldariomyces fumago. It produces caldariomycin, a chlorinated natural product (Butler and Sandy, 2009). The catalytic cycle of chloroperoxidase is initiated through the reaction of peroxide at the axial position of the Fe(III) complex, followed by the heterolytic O–O bond cleavage leading to the formation compound I. This compound is an oxoiron (IV)–porphyrin radical, or an oxoiron (IV)–protein radical, which is two oxidizing equivalents above the ferric state; meanwhile, hydrogen peroxide is reduced to water. The halide ion is then oxidized by compound I, yielding a transient Fe–OX intermediate (Compound X of peroxidases), and then hypohalous acid is released from the active site (Torres and Ayala, 2010). It is likely that hypohalous acid is freely diffusible and can therefore react with many substrates that are susceptible to electrophilic attack, which explain the lack of selectivity conferred by the enzyme (Fig. 16.1a). Through this mechanism, chloroperoxidase can halogenate several aromatic molecules such as polycyclic aromatic hydrocarbons, lignin and lignin model compounds, fulvic and humic acids, flavonoids and terpenes (Ayala et al., 2016). Reaction mechanism exhibited by halogenases (a) Heme dependent, (b) Vanadium dependent, (c) Flavin dependent, (d) Non-heme iron dependent, and (e) SAM dependent halogenases.
Role of Enzymes in the Bioremediation of Refractory Pollutants
Published in Maulin P. Shah, Removal of Refractory Pollutants from Wastewater Treatment Plants, 2021
Viresh R. Thamke, Ashvini U. Chaudhari, Kisan M. Kodam, Jyoti P. Jadhav
Chloroperoxidase (CPO) is a glycosylated hemoprotein containing an iron protoporphyrin IX (heme) as its prosthetic group and shares structural features with both cytochrome P450s and peroxidases. This structural feature makes CPO function as cytochrome P450 due to the activation of the ferric heme center in the CPO. In addition, CPO also undergoes peroxidations and two-electron oxidation typical of classical peroxidases and catalases, respectively [Figure 28.2(B)]. CPO was found to be significantly robust when compared to other peroxidases as well as harsh to other biocatalysts (Osborne et al. 2006).
Rapid and efficient enzymatic degradation of metsulfuron-methyl and its removal by bio-cascade treatment
Published in Bioremediation Journal, 2019
Jing Lu, Fengjiao Wang, Xuelian Li, Yichao Song, Ling Xiao, Yuebo Wang, Yucheng Jiang
In recent years, enzymatic degradation is regarded as an important alternative for treatment of wastewater because of its high efficiency and selectivity at mild reaction condition. Here, we present a very efficient enzymatic oxidation by chloroperoxidase (CPO) and H2O2 instead of the generally used chemical oxidation. The degraded products of metsulfuron-methyl were determined by high performance liquid chromatography-mass spectrometry (HPLC-MS) and the degradation route was outlined accordingly. The ecotoxicity test was carried out by measuring the growth-inhibitory effects (EC50) of the degraded solutions on a freshwater green alga, Chlorella pyrenoidosa. The proposed enzymatic degradation of metsulfuron-methyl was employed as a pre-stage treatment followed by activated sludge degradation, and this bio-cascade treatment was applied to the water samples containing metsulfuron-methyl to investigate the potential practical application.