Search

A porous silver nanostructure-supported ionic liquid-modified chloroperoxidase nanohybrid was successfully used in electroenzymatic tandem catalysis to achieve an efficient, mild, and stable approach for the conversion of nitrate into ammonia. [ABSTRACT FROM AUTHOR]

The operational stability of chloroperoxidase (CPO) was considerably enhanced by coupling with glucose oxidase (GOx) because H 2 O 2 could be generated in situ from glucose and oxygen. In this paper, a CPO–GOx nanoreactor was fabricated on the surface of Au@Fe 3 O 4 nanoparticles through layer-by-layer assembly using the specific avidin–biotin interaction. The X-ray diffraction data indicated the presence of both Fe and Au in the Au@Fe 3 O 4 carrier. The Au@Fe 3 O 4 displayed a uniform core/shell nanostructure, whereas the nanoparticles of the bienzymatic reactor were larger than the carrier. The catalytic activity of CPO was highly dependent on the structure of the enzymatic nanoreactor. The activity of Au@Fe 3 O 4 –GOx (inner)–CPO (outer) was 15.5% higher than that of Au@Fe 3 O 4 –CPO (inner)–GOx (outer). Moreover, Au@Fe 3 O 4 –GOx–CPO exhibited better thermostability. Au@Fe 3 O 4 –GOx–CPO retained 53.2% of its initial activity after incubation for 1.0 h at 60 °C and 30.4% of its initial activity after 18 h at 50 °C. Au@Fe 3 O 4 –GOx–CPO had good reusability. It retained more than 62.4% of its activity after the 12th cycle. This was attributed to the cage-like structure in Au@Fe 3 O 4 –GOx–CPO, which could effectively prevent the removal of the enzyme molecules from the carrier. [ABSTRACT FROM AUTHOR]

Abstract: Biotransformation of cyclohexene catalyzed by chloroperoxidase (CPO) from Caldariomyces fumago was employed to prepare value-added oxygenated derivative: trans-1,2-cyclohexanediol (CHD) using H2O2 as oxidants. The conversion of substrate was enhanced to 89.2% in the presence of small quantities of quaternary ammonium salts (QAS) compared to that of only 48.1% in aqueous phosphate buffer after 150min. The enhancement was dependent on the concentration and alkyl group length of QAS. QAS were found playing multiple functions in reaction media: phase transfer catalysis and tuning the composition of product. UV–vis, fluorescence and circular dichroism (CD) spectral assay were employed to investigate the effect of QAS on micro-environment around active center and structure of protein. The strengthening of α-helix structure of CPO and more exposure heme for easily access of substrate was found responsible for the improvement of catalytic performance of CPO. Moreover, the determined kinetic parameters indicated the affinity and selectivity of CPO to substrate was improved according to the observation of a decrease of Michaelis constant K m while an increase of the second order rate constants k cat/K m. The strategy reported in this work is environment-friendly, straightforward and applicable to large scale preparation. [Copyright &y& Elsevier]

The catalytic performance of chloroperoxidase (CPO) in peroxidation of 2, 2′-azinobis-(-3 ethylbenzothiazoline-6-sulfononic acid) diammonium salt (ABTS) and oxidation of indole in a reverse micelle composed of surfactant-water-isooctane-pentanol was investigated and optimized in this work. Some positive results were obtained as follows: the peroxidation activity of CPO was enhanced 248% and 263%, while oxidation activity was enhanced 215% and 222% in cetyltrimethylammonium bromide (CTABr) reverse micelle medium and dodecyltrimethylammonium bromide (DTABr) medium, respectively. Thermostability was also greatly improved in reverse micelle: at 40°C, CPO essentially lost all its activity after 5 h incubation, while 58-76% catalytic activity was retained for both reactions in the two reverse micelle media. At 50°C, about 44-75% catalytic activity remained for both reactions in reverse micelle after 2 h compared with no observed activity in pure buffer under the same conditions. The enhancement of CPO activity was dependent mainly on the surfactant concentration and structure, organic solvent ratio ( V/ V), and water content in the reverse micelle. The obtained kinetic parameters showed that the catalytic turnover frequency ( k) was increased in reverse micelle. Moreover, the lower K and higher k/ K demonstrated that both the affinity and specificity of CPO to substrates were improved in reverse micelle media. Fluorescence, circular dichroism (CD) and UV-vis spectra assays indicated that a catalytically favorable conformation of enzyme was achieved in reverse micelle, including the strengthening of the protein α-helix structure, and greater exposure of the heme prosthetic group for easy access of the substrate in bulk solution. These results are promising in view of the industrial applications of this versatile biological catalyst. [ABSTRACT FROM AUTHOR]

Chloroperoxidase(CPO) from Caldariomyces fumagocouldmediate a very efficient oxidative decolorization/degradationof aqueous azo dye. The decolorization efficiencies for Congo Redand Alizarin Yellow R reached 88.25% in 3 min and 92.38% in 5 min,respectively, under mild conditions at enzyme concentrations of 0.025and 0.03 μmol L–1, respectively. Comparedwith the typical mechanism involved in oxidative decolorization ofazo dyes catalyzed by other peroxidases, a different enzymatic catalyticcycle was found in this work. The oxidative decolorization was carriedout in bulk solution, which would get rid of the restriction of substraterequired by the channel access to the substrate pocket in the enzymaticactive site. Nine degradation products of Congo Red were detectedby HPLC–MS analysis, and two types of degradation pathwayswere proposed accordingly. The strong toleration of the typical saltspecies in industrial effluents by this system ensured that it haspotential applications in treatment of industrial wastewater. [ABSTRACT FROM AUTHOR]

Abstract: The decolorization/degradation of aqueous azo dyes generated by textile photography industries are a main issue in wastewater treatment. Despite many significant efforts and numerous systems have been exploited, the problem is still unsolved due to intrinsically low activity or use of non-convenient chemical reagents. Biodegradation appears to be one of the most efficient ways, however, the initial step of biotransformation usually involves a reductive cleavage of the azo bond, which under anaerobic conditions leads to the formation of aromatic amines known to be carcinogenic. This study shows that applying an oxidative process of H2O2 catalyzed by chloroperoxidase (CPO) for decolorization/degradation of aqueous azo dyes (Orange G and Sunset Yellow) in buffer solution is a very efficient system. The effect of initial pH, dosage of enzyme, H2O2 concentration, reaction temperature and time, and suitable initial dye concentration on the decolorization efficiency were investigated in detail and optimized accordingly. At optimum reaction condition, the decolorization efficiency of Orange G reached 98.72% in 5min, and 77.25% in 10min for Sunset Yellow. The dosage of CPO was below ppm level. This enzymatic reaction is an ideal potential alternative for application on decolorization/degradation of aqueous azo dyes. Furthermore, the elucidation of degradation pathways is of special interest considering healthy and environmental priorities. In this work, LC–MS was used to determine the structures of intermediates arising from Orange G by CPO–H2O2 oxidation. Eight transformation products were identified and two types of cleavage were proposed for the degradation pathway. [Copyright &y& Elsevier]

[Display omitted] • An efficient biosensor 3D-CNT@MoS 2 /IL EMB /CPO for H 2 O 2 detection. • 3D-CNT@MoS 2 increases the fixation site of the CPO while prevents it leaking. • CPO achieves direct electron transfer in the absence of a redox medium. • The biosensor is applied to the detection of H 2 O 2 in human urine. Enzyme-based electrochemical biosensors are promising for a wide range of applications due to their unique specificity and high sensitivity. In this work, we present a novel enzyme bioelectrode for the sensing of hydrogen peroxide (H 2 O 2). The molybdenum disulfide nanoflowers (MoS 2) is self-assembled on carboxylated carbon nanotubes (CNT) to form a three-dimensional conductive network (3D-CNT@MoS 2), which is modified with 1-ethyl-3-methylimidazolium bromide (IL EMB), and followed by anchoring chloroperoxidase (CPO) onto the nanocomposite (3D-CNT@MoS 2 /IL EMB) through covalent binding to form a bioconjugate (3D-CNT@MoS 2 /IL EMB /CPO). The IL EMB modified 3D-CNT@MoS 2 /IL EMB has good hydrophilicity and conductivity, which not only provides a suitable microenvironment for the immobilization of CPO but also facilitates the direct electron transfer (DET) of CPO at the electrode. The 3D-CNT@MoS 2 /IL EMB /CPO bioconjugate modified electrode has a high catalytic efficiency for H 2 O 2. Through electroenzymatic synergistic catalysis for H 2 O 2 detection by 3D-CNT@MoS 2 /IL EMB /CPO-GCE, a wide detection range of 0.2 μmol·L−1 to 997 μmol·L−1 and a low detection limit of 0.097 μmol･L−1 with high sensitivity of 1050 µA·mmol·L−1·cm−2 were achieved. Additionally, the 3D-CNT@MoS 2 /IL EMB /CPO-GCE displayed exceptional stability, selectivity, and reproducibility. Furthermore, 3D-CNT@MoS 2 /IL EMB /CPO-GCE is suitable for sensing of H 2 O 2 in human urine s with good recovery, suggesting its potential application for the detection of H 2 O 2 in biomedical field. [ABSTRACT FROM AUTHOR]

Trichloroacetic acid (TCA), as a by-product of chlorination disinfection, is a highly carcinogenic chemical. Due to the widespread use of chlorination disinfection, it is critical to detect TCA in drinking water to decrease the incidence of disease. In this work, we developed an efficient TCA biosensor via electroenzymatic synergistic catalysis. The porous carbon nanobowls (PCNB) are prepared and wrapped by an amyloid like proteins formed by phase-transitioned lysozyme (PTL-PCNB), then, chloroperoxidase (CPO) is abounding to PTL-PCNB owing to its strong adhesion. The ionic liquid of 1-ethyl-3-methylimidazolium bromide (IL EMB) is co-immobilized on PTL-PCNB to from CPO-IL EMB @PTL-PCNB nanocomposite to assist the direct electron transfer (DET) of CPO. The PCNB plays two roles here. In addition, to increasing the conductivity, it serves as an ideal support for holding CPO; The CPO-IL EMB @PTL-PCNB nanocomposite modified electrode presents high efficiency for sensing TCA. Through electroenzymatic synergistic catalysis, a wide detection range of 33 μmol L−1 to 98 mmol L−1 can be achieved with a low detection limit of 5.9 μmol L−1, and high stability, selectivity as well as reproducibility, which ensures its potential practical applicability. This work provides a new platform for the electro-enzyme synergistic catalysis in one pot. [Display omitted] • Porous carbon nanobowls for sensor of trichloroacetic acid by electroenzymatic catalysis. • Phase-transitioned lysozyme modified on carbon bowls for holding chloroperoxidase. • Ionic liquid assists direct electron transfer of chloroperoxidase without a redox mediator. • The nanocomposites modified electrode presents excellent performance for the TCA detection. [ABSTRACT FROM AUTHOR]

Graphical abstract Preparation and performance of CPO-GOx co-immobilized on MGO. Highlights • chloroperoxidase and glucose oxidase were co-immobilized onto the surface of MGO. • The catalytic efficiency of immobilized CPO was much superior to that of free CPO. • Immobilized CPO can be effectively and conveniently recovered and is ready to reuse. • Enzyme cascade helps to harness the power of enzymes requiring auxiliary proteins. Abstract Although chloroperoxidase (CPO) has long been recognized as a powerful and versatile catalyst, its applications have been thwarted by the difficulty in regenerating the active enzyme and substrate (peroxide) induced protein inactivation. In this paper, we describe the fabrication and characterization of chloroperoxidase (CPO) and glucose oxidase (GOx) on the surface of MGO. The performance of the immobilized CPO was considerably enhanced by coupling with GOx that provided the required H 2 O 2 in situ through glucose oxidation. The activity of MGO-GOx-CPO (96.6%) towards the decolorization of orange G was much superior to that of MGO-GOx+MGO-CPO (86.2%), probably as a result of reduced mass transfer resistance between CPO and H 2 O 2 generated from GOx molecules. Interestingly, MGO-GOx-CPO reached its peak activity (95.2%) when temperature was maintained between 42 °C and 50 °C compared to the optimal temperature of 35 °C for the free enzyme, possibly due to dispersion of the otherwise stacked MGO below 42 °C. Finally, MGO-GOx-CPO can be conveniently reused for its ease of recovery in the presence of an external magnetic field, with ∼38.5% activity remained after 6 cycles of applications. This work demonstrates the feasibility of co-immobilizing CPO and GOx onto MGO and the potential of MGO-GOx-CPO in environmental applications. [ABSTRACT FROM AUTHOR]

An enzyme–TiO 2 composite with high catalytic activity, stability at harsh reaction condition, and good reusability was prepared via modification of TiO 2 by polydopamine (PDA) to tethering with chloroperoxidase (CPO) or horseradish peroxidase (HRP) through glutaraldehyde. TiO 2 played both roles of solid carrier and photo-catalyst in the application of soluble dyes decolorization, and in this way, the loss of enzymatic activity during enzyme immobilization can be compensated. Because the enzyme and TiO 2 were included in same composites, an enzyme-photo bifunctional synergistic catalysis was observed due to the interaction between enzyme and TiO 2 , resulting in that the formation of catalytic intermidiate, OH, increased and the band gap energy of TiO 2 became narrow. The light absorption by TiO 2 was extended from the UV region to the visible region through coated by PDA and CPO/HRP so as that CPO/HRP-TiO 2 @PDA can be used under visible light irradiation instead of ultraviolet light irradiation, which can avoid the decrease of enzyme activity by ultraviolet light irradiation. HRP-TiO 2 @PDA composite had even the best resuability of enzyme immobilized on solid support compared with the data in reference, in our best knowledge. There was no activity loss of HRP-TiO 2 @PDA after 15 times use, and more than 90% activity can be remained after 25 times use. Even after 40 times use, the relative activity of HRP-TiO 2 @PDA was 63.6% of that in the first run. The difference of reusability between CPO and HRP have relationship with the distribution of function group among the surface of enzyme molecule. [ABSTRACT FROM AUTHOR]

• A very efficient GOx-CPO cascade catalysis for HClO generation. • The spatial distribution and proximity effect account for the high cascade efficiency. • PTL coating plays mutil-functions including concentrating intermediate and improving dispersibility. • The prepared biocomposite PTL@GOx&CPO@DMSP is very stable at harsh conditions. • Efficient anti-tumor effect and effectively in application of fruit preservation. Enzymatic cascades catalysis engenders complex and selective intracellular transformations due to the organization of the enzymes in confined cellular environments. In this work, a biomimetic strategy is employed to develop a synthetic cell analogue for operating multi-enzymatic cascade catalysis in vitro. The glucose peroxidase (GOx) and chloroperoxidase (CPO) are co-encapsulated in the channel of dendritic mesoporous silica nanoparticles (DMSP) modified by phase-transitioned lysozyme (PTL@GOx&CPO@DMSP). The cascade efficiency is substantially enhanced compared with the diffusion mixtures of the free enzymes in bulk solution due to some nanoscale construction, such as confinement effect, proximity effect and special distribution mode of the enzymes. The high specific surface area and high concentration of mesoporous cages in DMSP is beneficial for encapsulation of enzyme. The cross-linked cavities ensure directional transfer of the intermediate from GOx to CPO, known as "substrate channel". PTL plays multiple functions including inhibiting leaking of enzyme from DMSP, concentrating intermediate H 2 O 2 at DMSP domains and keeping this biocomposite stable in aqueous environment by improving its dispersibility. The prepared biocomposite PTL@GOx & CPO@DMSP is very stable at harsh conditions. It can retain 42% of original catalytic activity at 90°C with incubation for 3 h while the retained activity of free enzymes is only 5% under the same conditions. Meanwhile, it can keep 92.4% of its original catalytic activity after 10 reuses. These characteristics ensure practical application of this biocatalytic material. The active HClO generated by GOx-CPO cascade has an efficient anti-tumor effect and is effectively applied to preserve fruit. [Display omitted] [ABSTRACT FROM AUTHOR]

Electroenzymatic biosensors have wide applications due to its fastness and sensitivity. Here we propose a bio-nanocomposite to be dropped on glassy carbon electrode (GCE) for nitrite sensoring by electroenzymatic catalysis. The composite is constructed by ionic liquids (1-butyl-3-methylimidazolium bromide, IL BMB) modified chloroperoxidase (CPO) immobilized on gold nanoparticles (Au NPs) modified reduced graphene oxide (rGO). The IL BMB can facilitate the direct electron transfer (DET) of CPO on GCE without a redox mediator. The molecular docking indicates IL BMB is located at the opening of substrate channel rather than occupy the active site of CPO, which is beneficial to its DET. Circular dichroic spectrum (CD) verifies the α-helix content of CPO is increased, and ultraviolet-visible spectrum (UV–vis) demonstrates the heme prosthetic group become more exposed by IL BMB. These changes result in the enhancement of CPO activity. The rGO-Au NPs plays two roles enhancing the detection signal and improving the loading of CPO on GCE. The sensor (CPO-IL BMB /rGO-Au NPs/GCE) provides two models for nitrite detection as cyclic voltammetry and amperometry. The detection limit is 0.25 μmol·L−1 and 0.049 μmol·L−1, respectively with corresponding detection range of 2.0−2500 μmol·L−1 and 0.5–300 μmol·L−1. The high sensitivity, stability, and selectivity of this electroenzymatic biosensor ensure its potential practical application. [Display omitted] • CPO-IL BMB /rGO-Au NPs/GCE for efficient sensoring of nitrite by electroenzymatic catalysis. • IL BMB can effectively assist the direct electron transfer of CPO without a redox mediator. • The rGO-Au NPs composite plays two roles as enhancing detection signal and improving CPO loading. • The enzymatic sensor shows a low detection limit in a wide range with high stability and selectivity. [ABSTRACT FROM AUTHOR]