Immobilization of invertase in conducting copolymers of 3-methylthienyl methacrylate

An immobilized invertase enzyme for the selective determination of sucrose in fruit juices

Poly(N-vinylpyrrolidone-co-butylacrylate-co-N-hydroxymethylacrylamide) has been synthesized by free radical polymerization at 70 °C. Copolymer were characterized by FT-IR, elemental analysis and viscometric methods. Invertase was immobilized onto poly(N-vinyl pyrrolidone-co-butyl acrylate-co-N-hydroxymethyl acrylamide) by entrapment method. Optimum parameters (pH, temperature, substrate concentration, amount of polymer) for immobilization to obtain maximum activity were investigated. Kinetic parameters, K_m and V_max, of the free and immobilized invertases were also assayed. Results showed that immobilization enhanced the enzyme stability against changes of pH and temperature and immobilized enzyme showed lower K_m value than free enzyme. One of the most interesting results is that the optimum operational temperature of the immobilized enzyme was 15 °C higher than that of the free enzyme. The next is the activity of the immobilized enzyme at the optimum temperature (70 °C) was approximately the same as the activity of the free enzyme at its optimum temperature (55 °C). Finally, immobilized invertase were used for determination of sucrose in commercial fruit juices. A new method and equation based on immobilized invertase were derived for determination of sucrose in commercial cheryy and pomegranate juices.

l-Asparaginase production in rotating bed reactor from Rhizopus microsporus IBBL-2 using immobilized Ca-alginate beads

The present work reports on the production of extracellular l-asparaginase from Rhizopus microsporus IBBL-2 using submerged fermentation (SmF) process free of glutaminase and urease activities. Primary studies done in shake flask showed that the highest l-asparaginase activity of 12.68 U mL^-1 was produced at 72 h with optimized fermentation parameters such as pH 6.0, 4 × 10⁶ fungal cells mL^-1, and agitation of 180 rpm at 30 °C using one-factor-at-a-time (OFAT). Different substrates, nitrogen sources, temperature, pH, the initial number of cells and metal ions were tested to determine the impact on enzyme production. l-Asparaginase activity of 17.68 U mL^-1 was produced after 48 h using immobilized calcium-alginate (Ca-alginate) cells. 4 × 10⁶ cells mL^-1 was entrapped in 3% (W/V) of alginate bead of size 2 mm each at a temperature of 30 °C and pH of 6. The process was optimized using L9 (3⁴) Taguchi Orthogonal Array (OA) technique with a regression coefficient (R ²) value of 0.9709, F value of 33.34 and p value of 0.0025. Scale-up studies involving 200-mL and 1-L rotating bed reactor (RBR) using immobilized beads were done and the results obtained are 20.21 U mL^-1 and 19.13 U mL^-1, respectively, the increased activity with immobilization accounts for reduced shear on cells due to increased stability as compared to the free-flowing cells.

Aspergillus niger PA2 Tyrosinase Covalently Immobilized on a Novel Eco-Friendly Bio-Composite of Chitosan-Gelatin and Its Evaluation for L-DOPA Production

Tyrosinase (EC 1.14.18.1) a copper-containing monooxygenase, isolated from a fungal isolate Aspergillus niger PA2 was subjected for immobilization onto a composite consisting of chitosan and gelatin biopolymers. The homogeneity of the chitosan-gelatin biocomposite film was characterized by X-ray diffraction analyses. To evaluate immobilization efficiency, chitosan-gelatin-Tyr bio-composite films were analyzed by field emission scanning electron microscopy, atomic force microscopy and UV-spectroscopy. The rough morphology of the film led to a high loading of enzyme and it could retain its bioactivity for a longer period. The enzyme adsorbed onto the film exhibited 72% of its activity after 10 days and exhibited good repeatability for up to nine times, after intermittent storage. Moreover, the immobilized enzyme exhibited broader pH and temperature profile as compared to free counterpart. Immobilized enzyme was further evaluated for the synthesis of L-DOPA (2,4-dihydroxy phenylalanine) which is a precursor of dopamine and a potent drug for the treatment of Parkinson's disease and for myocardium neurogenic injury.

Enzyme immobilization: an update

Compared to free enzymes in solution, immobilized enzymes are more robust and more resistant to environmental changes. More importantly, the heterogeneity of the immo-bilized enzyme systems allows an easy recovery of both enzymes and products, multiple re-use of enzymes, continuous operation of enzymatic processes, rapid termination of reactions, and greater variety of bioreactor designs. This paper is a review of the recent literatures on enzyme immobilization by various techniques, the need for immobilization and different applications in industry, covering the last two decades. The most recent papers, patents, and reviews on immobilization strategies and application are reviewed.

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.

Preparation and properties of invertase immobilized on a poly(maleic anhydride-hexen-1) membrane

Poly(maleic anhydride-alt-hexen-1)(poly(MA-alt-H-1)) has been synthesized by radical polymerization and characterized by DSC, FT-IR, acid number determination, viscometric and NMR methods. Data showed that the co-polymer is an alternating co-polymer whose composition does not depend on the monomer feed composition. Invertase was immobilized onto a poly(MA-alt-H-1) membrane via glutaraldehyde and bovine serum albumin. The Km value of poly(MA-alt-H-1)-invertase was approximately 4.4-fold higher than the free enzyme, indicating decreased affinity by the invertase for its substrate (sucrose), whereas Vmax was lower for the immobilized invertase. Immobilization improved the pH stability of the enzyme, as well as its temperature stability. Immobilized samples obtained were stable and could be used many times over a period of 2 months without considerable activity loss.

Kinetics study of invertase covalently linked to a new functional nanogel

Nanogels are promising materials as supports for enzyme immobilization. A new hydrogel comprising of methacrylic acid (MAAc) and N-vinyl pyrrolidone (N-VP) and ethyleneglycol dimethacrylate (EGDMA) was synthesized and converted to nanogel by an emulsification method. Nanogel was further functionalized by Curtius azide reaction for use as support for the covalent immobilization of invertase (Saccharomyces cerevisiae). As-prepared or invertase-immobilized nanogel was characterized by FTIR, XRD, TEM and nitrogen analysis. The characterization of both free and the immobilized-invertase were performed using a spectrophotometric method at 540 nm. The values of V(max), maximum reaction rate, (0.123 unit/mg), k(m), Michaelis constant (7.429 mol/L) and E(a), energy of activation (3.511 kj/mol) for the immobilized-invertase are comparable with those of the free invertase at optimum conditions (time 70 min, pH 6.0 and temperature 45°C). The covalent immobilization enhanced the pH and thermal stability of invertase. The immobilized biocatalyst was efficiently reused up to eight cycles.

Chemically surface modified gel (CSMG): An excellent enzyme-immobilization matrix for industrial processes

Invertase from S. cerevisiae has been immobilized on porous silica matrix, formed using sol-gel chemistry, with surface area of approximately 650 m(2)/g. The co-condensation of silica sol with 3-aminopropyl(triethoxy)silane produced an amino-chemically surface modified silica gel (N-CSMG) with a very high ligand loading of 3.6 mmol/g SiO(2); significantly higher than commercially available matrices. Surface amine groups were activated with glutaraldehyde to produce GA-N-CSMG, and invertase covalently attached by the aldehyde. Invertase was used as a model enzyme to measure the immobilizing character of the GA-N-CSMG material. Using an optimized immobilization protocol, a very high loading of 723 mg invertase per gram GA-N-CSMG is obtained; 3-200-fold higher than values published in literature. The reproducible, immobilized activity of 246,000 U/g GA-N-CSMG is also greater than any other in literature. Immobilized invertase showed almost 99% retention of free enzyme activity and no loss in catalytic efficiency. The apparent kinetic parameters K(M) and V(M) were determined using the Michealis-Menten kinetic model. K(M) of the free invertase was 1.5 times greater than that of the immobilized invertase--indicating a higher substrate affinity of the immobilized invertase. These findings show considerable promise for this material as an immobilization matrix in industrial processes.

Biosensing approach for alcohol determination using immobilized alcohol oxidase

Alcohol oxidase (AOD) was immobilized in polypyrrole (PPy) and a random copolymer containing 3-methylthienyl methacrylate and p-vinylbenzyloxy poly(ethyleneoxide) matrices. Immobilization of enzyme was performed via entrapment in conducting polymers during electrochemical polymerization of pyrrole through the thiophene moiety of the copolymer. Three different alcohols, namely methanol, ethanol and n-propanol, were used as substrates. Maximum reaction rates, Michaelis-Menten constants, optimum temperature and pH values, operational stabilities and shelf life of the enzyme electrodes were investigated.

Preventing inhibition of tyrosinase with modified electrodes

Wines, especially red wines, contain numerous biologically active compounds, the most important of which are polyphenols, whose nutritional importance is attributed to their antioxidant power. Because of this, the detection of the amount of phenolic compounds in red wines becomes extremely important. However, using free enzyme in the determination of phenolic compounds in wines cannot reflect the actual values since there are also naturally found inhibitors in red wines. In this study, benzoic acid, cinnamic acid, and sorbic acid were utilized to understand the behavior of immobilized polyphenol oxidase in the conducting polymer matrices toward inhibition. Cinnamic acid was found to be the most powerful inhibitor for both free and immobilized enzyme in copolymer matrix of poly(terephthalic acid bis-(2-thiophen-3-yl-ethyl) ester) (PTATE) with polypyrrole (PPy). In the case of immobilized enzyme in PPy matrix, it was observed that sorbic acid is a stronger inhibitor than cinnamic acid. The inhibitory effects of these inhibitors on PPO were compared with respect to both the structural differences of inhibitors and conducting polymer matrices.

Immobilization of tyrosinase in polysiloxane/polypyrrole copolymer matrices

Immobilization of tyrosinase in conducting copolymer matrices of pyrrole functionalized polydimethylsiloxane/polypyrrole (PDMS/PPy) was achieved by electrochemical polymerization. The polysiloxane/polypyrrole/tyrosinase electrode was constructed by the entrapment of enzyme in conducting matrices during electrochemical copolymerization. Maximum reaction rate (V(max)) and Michaelis-Menten constant (K(m)) were investigated for immobilized enzyme. Enzyme electrodes were prepared in two different electrolyte/solvent systems. The effect of supporting electrolytes, p-toluene sulfonic acid and sodium dodecyl sulfate on the enzyme activity and film morphology were determined. Temperature and pH optimization, operational stability and shelf-life of enzyme electrodes were also examined. Phenolic contents of green and black tea were determined by using enzyme electrodes.