Effects of the immobilization supports on the catalytic properties of immobilized mushroom tyrosinase: a comparative study using several substrates

Purification and characterization of novel isoforms of the polyphenol oxidase from Malus domestica fruit pulp

Polyphenol oxidases (PPOs), belong to the group of oxidoreductases that are copper containing enzymes and are responsible for plant browning. PPOs are extensively distributed in plant kingdom and can oxidize wide range of aromatic compounds of industrial importance. The aim of this study was purification and characterization of PPO isoforms from the fruit pulp of Golden delicious apple. High performance liquid chromatography was used to purify the two novel isoforms of PPO and further their molecular weights (45 and 28 kDa) were determined using sodium dodecyl sulfate polyacrylamide gel electrophoresis. The purified isoforms have optimum pH (6.5), optimum temperature (40°C), the Vmax (4.45 μM/min) and Km (74.21 mM) with catechol substrate. The N-terminal microsequences of both PPO isoforms were determined using a pulse liquid protein sequencer and found to be AKITFHG (28 kDa) and APGGG (45 kDa). Polyphenol oxidases are efficiently used in the pharmaceutical, paper and pulp, textiles and food industries. Recently, the PPOs have been used for bioremediation and in the development of biosensors.

Biological oxidation methods for the removal of organic and inorganic contaminants from wastewater: A comprehensive review

Enzyme-based bioremediation is a simple, cost-effective, and environmentally friendly method for isolating and removing a wide range of environmental pollutants. This study is a comprehensive review of recent studies on the oxidation of pollutants by biological oxidation methods, performed individually or in combination with other methods. The main bio-oxidants capable of removing all types of pollutants, such as organic and inorganic molecules, from fungi, bacteria, algae, and plants, and different types of enzymes, as well as the removal mechanisms, were investigated. The use of mediators and modification methods to improve the performance of microorganisms and their resistance under harsh real wastewater conditions was discussed, and numerous case studies were presented and compared. The advantages and disadvantages of conventional and novel immobilization methods, and the development of enzyme engineering to adjust the content and properties of the desired enzymes, were also explained. The optimal operating parameters such as temperature and pH, which usually lead to the best performance, were presented. A detailed overview of the different combination processes was also given, including bio-oxidation in coincident or consecutive combination with adsorption, advanced oxidation processes, and membrane separation. One of the most important issues that this study has addressed is the removal of both organic and inorganic contaminants, taking into account the actual wastewaters and the economic aspect.

Polyamide-Laccase Nanofiber Membrane for Degradation of Endocrine-Disrupting Bisphenol A, 17α-ethinylestradiol, and Triclosan

Contamination of potable water by endocrine disrupting chemicals (EDCs) is a growing problem worldwide. One of the possible treatments is the utilization of laccase enzyme catalyzing oxidation of phenolic structures of EDC when anchored in a polymeric nanofiber membrane. Previous studies failed to develop a membrane with a sufficiently active enzyme, or the immobilization process was too complicated and time-consuming. Here, we established an elegant method for immobilizing Trametes versicolor laccase onto polyamide 6 nanofibers (PA6-laccase) via adsorption and glutaraldehyde crosslinking, promoting high enzyme activity and easier applicability in water treatment technology. This simple and inexpensive immobilization ensures both repeated use, with over 88% of initial activity retained after five ABTS catalytic cycles, and enhanced storage stability. PA6-laccase was highly effective in degrading a 50-µM EDC mixture, with only 7% of bisphenol A, 2% of 17α-ethinylestradiol, and 30% of triclosan remaining after a 24-h catalytic process. The PA6-laccase membrane can lead to the improvement of novel technologies for controlling of EDC contamination in potable water.

Fabrication of the robust and recyclable tyrosinase-harboring biocatalyst using ethylenediamine functionalized superparamagnetic nanoparticles: nanocarrier characterization and immobilized enzyme properties

Immobilized tyrosinase onto the functionalized nanoparticles with the ability to be reused easily in different reaction cycles to degrade phenolic compounds is known as a substantial challenge, which can be overcome through surface modification of the particles via proper chemical groups. Herein, the synthesis and silica coating of superparamagnetic nanoparticles using a simple procedure as well as their potential for tyrosinase immobilization were demonstrated. Therefore, N-[3-(trimethoxysilyl)propyl]ethylenediamine was used to functionalize the silica-coated nanoparticles with amine groups. Then, the ethylenediamine functionalized magnetic nanoparticles (EMNPs) were suspended in a solution containing tetrahydrofuran and cyanuric chloride (as an activating agent) to modify nanocarriers. To immobilize enzyme, a mixture of tyrosinase and cyanuric chloride functionalized magnetic nanoparticle (Cyc/EMNPs) was shaken at room temperature. The particles were characterized by EDX, TGA, SEM, FTIR, and TEM. As a result, the successful functionalization of the magnetic nanoparticles and covalent attachment of tyrosinase onto the Cyc/EMNPs were confirmed. The fabricated nano-biocatalyst particles were semi-spherical in shape. The immobilized tyrosinase (Ty-Cyc/EMNPs) exhibited remarkable reusability of six consecutive reaction cycles while no considerable loss of activity was observed for the first three cycles. Moreover, the excellent stability of the biocatalyst at different temperatures and pHs was proved. The Ty-Cyc/EMNPs with interesting features are promising for practical applications in biosensor development and wastewater treatment.

Efficient purification of a highly active H-subunit of tyrosinase from Agaricus bisporus

A highly-active tyrosinase (H subunit) isoform has been purified from a commercial crude extract of Agaricus bisporus by a specific, two step-hydrophobic chromatography cascade process based on the differential adsorption of the proteins from the extract to hydrophobic-functionalized supports. At first, commercial, crude tyrosinase from Agaricus bisporus (AbTyr) dissolved in aqueous media was added to octadecyl-Sepabeads matrix at 25 °C. Under these conditions, the support specifically adsorbed a protein with a molecular weight of 47 kDa which showed no tyrosinase activity. The known H subunit of tyrosinase from Agaricus bisporus (45 kDa, H-AbTyr) and another protein of 50 kDa were present in the supernatant. Sodium phosphate buffer was added to adjust the ionic strength of the solution up to 100 mM and Triton X-100 was added (final concentration of 0.07% v/v) to control the hydrophobicity effect for both proteins. This solution was offered again to fresh octadecyl-Sepabeads support, immobilizing selectively the H-AbTyr and leaving exclusively the 50 kDa protein as a pure sample in the supernatant. This tyrosinase isoform of 50 kDa was almost 4-fold more active than the known H-TyrAb, with a specific tyrosinase activity of more than 38,000 U/mg.

Cinnamate of inulin as a vehicle for delivery of colonic drugs

Colon diseases are difficult to treat because oral administrated drugs are absorbed at the stomach and intestine levels and they do not reach colon; in addition, intravenous administrated drugs are eliminated from the body before reaching colon. Inulin is a naturally occurring polysaccharide found in many plants. It consists of β 2-1 linked D-fructose molecules having a glucosyl unit at the reducing end. Various inulin and dextran hydrogels have been developed that serve as potential carrier for introduction of drugs into the colon. Because inulin is not absorbed in the stomach or in the small intestine, and inulin is degraded by colonic bacteria, drugs encapsulated in inulin-coated vesicles could be specifically liberated in the colon. Therefore, the use of inulin-coated vesicles could represent an advance for the treatment of colon diseases. Here, we study the use of a cinnamoylated derivative of chicory inulin as a vehicle for the controlled delivery of colonic drugs. The encapsulation of methotrexate in inulin vesicles and its release and activity was studied in colon cancer cells in cultures.

Immobilization of tyrosinase on modified diatom biosilica: enzymatic removal of phenolic compounds from aqueous solution

Acid and plasma treated diatom-biosilica particles, were modified with 3-aminopropyl triethoxysilane (APTES), and activated with glutaraldehyde. Then, tyrosinase was immobilized onto the pre-activated biosilica by covalent bonding. The biosilica properties were determined using SEM, and FTIR. The enzyme system has been characterized as a function of pH, temperature and substrate concentration. Optimum pH of the free and immobilized enzyme was found to be pH 7.0. Optimum temperatures of the free and immobilized enzymes were determined as 35 and 45 °C respectively. The biodegradation of phenolic compounds (i.e., phenol, para-cresol and phenyl acetate) has been studied by means of immobilized tyrosinase in a batch system. The immobilized tyrosinase retained about 74% of its original activity after 10 times repeated use in the batch system. Moreover, the storage stability of the tyrosinase-biosilica system resulted excellent, since they maintained more than 67% of the initial activity after eighth week storage. Highly porous structure of biosilica can provide large surface area for immobilization of high quantity enzyme. The porous structure of the biosilica can decrease diffusion limitation both substrate phenols and their products. Finally, the immobilized tyrosinase was used in a batch system for degradation of three different phenols.

The Effect of D-(-)-arabinose on Tyrosinase: An Integrated Study Using Computational Simulation and Inhibition Kinetics

Tyrosinase is a ubiquitous enzyme with diverse physiologic roles related to pigment production. Tyrosinase inhibition has been well studied for cosmetic, medicinal, and agricultural purposes. We simulated the docking of tyrosinase and D-(−)-arabinose and found a binding energy of −4.5 kcal/mol for theup-formof D-(−)-arabinose and −4.4 kcal/mol for thedown-form of D-(−)-arabinose. The results of molecular dynamics simulation suggested that D-(−)-arabinose interacts mostly with HIS85, HIS259, and HIS263, which are believed to be in the active site. Our kinetic study showed that D-(−)-arabinose is a reversible, mixed-type inhibitor of tyrosinase (α-value  = 6.11 ± 0.98, K_i = 0.21 ± 0.19 M). Measurements of intrinsic fluorescence showed that D-(−)-arabinose induced obvious tertiary changes to tyrosinase (binding constant K = 1.58 ± 0.02 M⁻¹, binding number n = 1.49 ± 0.06). This strategy of predicting tyrosinase inhibition based on specific interactions of aldehyde and hydroxyl groups with the enzyme may prove useful for screening potential tyrosinase inhibitors.

Immobilization of laccase onto spacer-arm attached non-porous poly(GMA/EGDMA) beads: application for textile dye degradation

Non-porous poly(glycidyl methacrylate/ethyleneglycol dimetacrylate) (poly(GMA/EGDMA)) beads were prepared by suspension polymerization. The enzyme (i.e. laccase) was covalently immobilized onto plain and spacer-arm attached poly(GMA/EGDMA) beads. The amount of immobilized enzyme on the plain and spacer-arm attached beads was determined as 5.6 and 4.9 mg/g, respectively. The maximum activity (V(max)) and Michaelis constant (K(m)) of laccase immobilized on the spacer-arm attached beads, were found to be 77.6 U/min and 0.47 mM, respectively. Finally, the immobilized laccase was operated in a batch system, and textile dye Reactive Red 120 was successfully decolorized in the enzyme reactor.

Mixed ceria-based metal oxides biosensor for operation in oxygen restrictive environments

The unique catalytic, electrochemical, and oxygen storage properties of ceria and mixed ceria/titania hybrid composites were used to fabricate a new type of electrochemical enzyme biosensor. These materials provided increased analytical performance and possibilities for operation in oxygen-free conditions of an oxidase enzyme biosensor using tyrosinase as a model example. The investigation of the enzymatic reaction in the presence and absence of oxygen was first carried out using cyclic voltammetry. The results were used to identify the role of each metal oxide in the immobilization matrix and fabricate a simple amperometric tyrosinase biosensor for the detection of phenol and dopamine. The biosensor was optimized and characterized with respect to response time, detection limit, linear concentration range, sensitivity, and kinetic parameters. The detection limit for phenol was in the nanomolar range, with a detection limit of 9.0 x 10(-9) M and a sensitivity of 86 mA M(-1) in the presence of oxygen and of 5.6 x 10(-9) M and a sensitivity of 65 mA M(-1) in the absence of oxygen. The optimized biosensor also showed selective determination of the neurotransmitter dopamine with a detection limit of 3.4 x 10(-8) M and a sensitivity of 14.9 mA M(-1) in the presence of oxygen and of 4.2 x 10(-8) M and 14.8 mA M(-1) in the absence of oxygen. This strategy shows promise for increasing the sensitivity of oxidase enzyme sensors and provides opportunities for operation in oxygen limited conditions. It can also be extended for the development of other enzyme biosensors.

Immobilization of recombinant invertase (re-INVB) from Zymomonas mobilis on D-sorbitol cinnamic ester for production of invert sugar

The recombinant invertase (re-INVB) from Zymomonas mobilis was immobilized by adsorption onto the totally cinnamoylated derivative of D-sorbitol. The polymerization and cross-linking of the derivative initially obtained was achieved by irradiation in the ultraviolet region, where this prepolymer shows maximum sensitivity. Immobilization of re-INVB on this support involves a process of physical adsorption and intense hydrophobic interactions between the cinnamoyl groups of the support and related groups of the enzyme. Enzyme concentration, immobilization time, and irradiation time were important parameters affecting the immobilization efficiency. The optimum reaction pH of immobilized enzyme was 5, and the optimal reaction temperature was 40 degrees C. The apparent Michaelis constant and the apparent catalytic constant of re-INVB immobilized on the SOTCN derivative acting on sucrose was 78+/-5 mM and 5x10(4)+/-3x10(2) s(-1), respectively, while for the free enzyme, it was 98.0+/-4 mM and 1.2x10(4)+/-2.5x10(2) s(-1), respectively, suggesting a better apparent affinity of the enzyme for the substrate and a better hydrolysis rate when immobilized than when in solution. Immobilized re-INVB also showed good thermal stability and good operational stability (40% of the initial activity remaining after 45 cyles of 1 min duration and 90.6 mg of sucrose being hydrolyzed in 45 min per 2.5 mg of immobilized protein). The results showed that cinnamic carbohydrate esters of D-sorbitol are an appropriate support for re-INVB immobilization and the production of invert sugar.