Immobilization of tyrosinase and alcohol oxidase in conducting copolymers of thiophene functionalized poly(vinyl alcohol) with pyrrole

Immobilised Inulinase from Aspergillus niger for Fructose Syrup Production: An Optimisation Model

Fructose is a carbohydrate with essential applications in the food industry, mainly due to its high sweetness and low cost. The present investigation focused on optimising fructose production from commercial inulin using the enzymatic immobilisation method and applying the response surface methodology in a 12-run central composite design. The independent variables evaluated were the pH (-) and temperature (°C). The substrate consisted of a commercial inulin solution at a concentration of 1 g/L, while the catalyst consisted of the enzyme inulinase from Aspergillus niger (EC 232-802-3), immobilised in 2% m/v sodium alginate. A stirred vessel reactor was used for 90 min at 120 rpm, and quantification of reducing sugars was determined using DNS colorimetric and UV-Vis spectrophotometric methods at a 540 nm wavelength. After applying the response surface methodology, it was determined that the catalytic activity using the immobilisation method allows for a maximum total productivity of 16.4 mg/h under pH and temperature of 3.9 and 37 °C, respectively, with an efficiency of 96.4%. The immobilised enzymes' reusability and stability compared to free enzymes were evaluated, obtaining activity up to the fifth reuse cycle and showing significant advantages over the free catalyst.

Characterization of immobilized tyrosinase - an enzyme that is stable in organic solvent at 100 °C

Tyrosinase is a copper-containing enzyme present in plant and animal tissues, which catalyzes the production of melanin and other pigments. In organic solvent, tyrosinase can convert N-acetyl-l-tyrosine ethyl ester (insoluble in aqueous) to a derivative of l-dopamine (a drug used for the treatment of Parkinson's disease). Thus, the performances of tyrosinase in organic solvent have attracted scientific attention since 1980. In this work, we investigated the stability of immobilized tyrosinase at high temperature in anhydrous organic solvent. Triethylaminoethyl cellulose (TEAE-Cellulose) performed the best out of six immobilization platforms. The dry immobilized tyrosinase became extremely thermostable in organic solvent, and the half-life of the dry immobilized tyrosinase in organic solvent is strongly related to the polarity of the organic solvent than their log P value. The immobilized tyrosinase loses its activity instantaneously in aqueous solution at 100 °C, but it keeps enzymatic activity within 10 min in hydrophilic methanol and over one month in hydrophobic hexane (log P: 4.66, non-polar) even incubating at 100 °C. This research provides valuable information for the design of new biocatalysts.

Immobilized tyrosinase in hexane can withstand 100 °C over one week, and the half-life of the dry immobilized tyrosinase in organic solvent is strongly related to the polarity of the organic solvent.

Synthesis and characterization of Ogataea thermomethanolica alcohol oxidase immobilized on barium ferrite magnetic microparticles

Alcohol oxidase catalyzes the oxidation of primary alcohols into the corresponding aldehydes, making it a potential biocatalyst in the chemical industry. However, the high production cost and poor operational stability of this enzyme are limitations for industrial application. Immobilization of enzyme onto solid supports is a useful strategy for improving enzyme stability. In this work, alcohol oxidase from the thermotolerant methylotrophic yeast Ogataea thermomethanolica (OthAOX) was covalently immobilized onto barium ferrite (BaFe₁₂O₁₉) magnetic microparticles. Among different conditions tested, the highest immobilization efficiency of 71.0 % and catalytic activity of 34.6 U/g was obtained. Immobilization of OthAOX onto magnetic support was shown by Fourier-Transformed infrared microscopy, scanning electron microscopy and X-ray diffraction. The immobilized OthAOX worked optimally at 55 °C and pH 8.0. Immobilization also improved thermostability, in which >65% of the initial immobilized enzyme activity was retained after 24 h pre-incubation at 45 °C. The immobilized enzyme showed a greater catalytic efficiency for oxidation of methanol and ethanol than free enzyme. The immobilized enzyme could be recovered by magnetization and recycled for at least three consecutive batches, after which 70% activity remained. The properties of the immobilized enzyme suggest its potential industrial application for synthesis of aldehyde.

Advances in developing rapid, reliable and portable detection systems for alcohol

Development of portable, reliable, sensitive, simple, and inexpensive detection system for alcohol has been an instinctive demand not only in traditional brewing, pharmaceutical, food and clinical industries but also in rapidly growing alcohol based fuel industries. Highly sensitive, selective, and reliable alcohol detections are currently amenable typically through the sophisticated instrument based analyses confined mostly to the state-of-art analytical laboratory facilities. With the growing demand of rapid and reliable alcohol detection systems, an all-round attempt has been made over the past decade encompassing various disciplines from basic and engineering sciences. Of late, the research for developing small-scale portable alcohol detection system has been accelerated with the advent of emerging miniaturization techniques, advanced materials and sensing platforms such as lab-on-chip, lab-on-CD, lab-on-paper etc. With these new inter-disciplinary approaches along with the support from the parallel knowledge growth on rapid detection systems being pursued for various targets, the progress on translating the proof-of-concepts to commercially viable and environment friendly portable alcohol detection systems is gaining pace. Here, we summarize the progress made over the years on the alcohol detection systems, with a focus on recent advancement towards developing portable, simple and efficient alcohol sensors.

L-Dopa synthesis catalyzed by tyrosinase immobilized in poly(ethyleneoxide) conducting polymers

1-3,4-Dihydroxy phenylalanine called as l-Dopa is a precursor of dopamine and an important neural message transmitter and it has been a preferred drug for the treatment of Parkinson's disease. In this study, with regards to the synthesis of L-Dopa two types of biosensors were designed by immobilizing tyrosinase on conducting polymers: thiophene capped poly(ethyleneoxide)/polypyrrole (PEO-co-PPy) and 3-methylthienyl methacrylate-co-p-vinylbenzyloxy poly(ethyleneoxide)/polypyrrole (CP-co-PPy). PEO-co-PPy and CP-co-PPy were synthesized electrochemically and tyrosinase immobilized by entrapment during electropolymerization. L-Tyrosine was used as the substrate for L-Dopa synthesis. The kinetic parameters of the designed biosensors, maximum reaction rate of the enzyme (Vmax) and Michaelis Menten constant (Km) were determined. Vmax were found as 0.007 μmol/(minelectrode) for PEO-co-PPy matrix and 0.012 μmol/(minelectrode) for CP-co-PPy matrix. Km values were determined as 3.4 and 9.2 mM for PEO-co-PPy and CP-co-PPy matrices, respectively. Optimum temperature and pH, operational and shelf life stabilities of immobilized enzyme were also examined.

Review paper: Progress in the Field of Conducting Polymers for Tissue Engineering Applications

This review focuses on one of the most exciting applications area of conjugated conducting polymers, which is tissue engineering. Strategies used for the biocompatibility improvement of this class of polymers (including biomolecules’ entrapment or covalent grafting) and also the integrated novel technologies for smart scaffolds generation such as micropatterning, electrospinning, self-assembling are emphasized. These processing alternatives afford the electroconducting polymers nanostructures, the most appropriate forms of the materials that closely mimic the critical features of the natural extracellular matrix. Due to their capability to electronically control a range of physical and chemical properties, conducting polymers such as polyaniline, polypyrrole, and polythiophene and/or their derivatives and composites provide compatible substrates which promote cell growth, adhesion, and proliferation at the polymer—tissue interface through electrical stimulation. The activities of different types of cells on these materials are also presented in detail. Specific cell responses depend on polymers surface characteristics like roughness, surface free energy, topography, chemistry, charge, and other properties as electrical conductivity or mechanical actuation, which depend on the employed synthesis conditions. The biological functions of cells can be dramatically enhanced by biomaterials with controlled organizations at the nanometer scale and in the case of conducting polymers, by the electrical stimulation. The advantages of using biocompatible nanostructures of conducting polymers (nanofibers, nanotubes, nanoparticles, and nanofilaments) in tissue engineering are also highlighted.

Enzymatic removal of phenol and p-chlorophenol in enzyme reactor: horseradish peroxidase immobilized on magnetic beads

Horseradish peroxidase was immobilized on the magnetic poly(glycidylmethacrylate-co-methylmethacrylate) (poly(GMA-MMA)), via covalent bonding and used for the treatment of phenolic wastewater in continuous systems. For this purposes, horseradish peroxidase (HRP) was covalently immobilized onto magnetic poly(GMA-MMA) beds using glutaraldehyde (GA) as a coupling agent. The maximum HRP immobilization capacity of the magnetic poly(GMA-MMA)-GA beads was 3.35 mg g(-1). The immobilized HRP retained 79% of the activity of the free HRP used for immobilization. The immobilized HRP was used for the removal of phenol and p-chlorophenol via polymerization of dissolved phenols in the presence of hydrogen peroxide (H(2)O(2)). The effect of pH and temperature on the phenol oxidation rate was investigated. The results were compared with the free HRP, which showed that the optimum pH value for the immobilized HRP is similar to that for the free HRP. The optimum pH value for free and immobilized HRP was observed at pH 7.0. The optimum temperature for phenols oxidation with immobilized HRP was between 25 and 35 degrees C and the immobilized HRP has more resistance to temperature inactivation than that of the free form. Finally, the immobilized HRP was operated in a magnetically stabilized fluidized bed reactor, and phenols were successfully removed in the enzyme reactor.