Jakub Zdarta

Enzyme immobilization by adsorption: a review

Endowed with unparalleled high catalytic activity and selectivity, enzymes offer enormous potential as catalysts in practical applications. These applications, however, are seriously hampered by enzymes’ low thermal and chemical stabilities. One way to improve these stabilities is the enzyme immobilization. Among various tested methods of this process that make use of different enzyme-carrier interactions, immobilization by adsorption on solid carriers has appeared most common. According to these findings, in this review we present a comparative analysis of the literature reports on the recent trends in the immobilization of the enzymes by adsorption. This thorough study was prepared in order to provide a deeper understanding of the process. Both carriers, carrier modifiers and procedures developed for effective adsorption of the enzymes are discussed. The review may thus be helpful in choosing the right adsorption scheme for a given enzyme to achieve the improvement of its stability and activity for a specific application.

Chitin-Lignin Material as a Novel Matrix for Enzyme Immobilization

Innovative materials were made via the combination of chitin and lignin, and the immobilization of lipase from Aspergillus niger. Analysis by techniques including FTIR, XPS and 13C CP MAS NMR confirmed the effective immobilization of the enzyme on the surface of the composite support. The electrokinetic properties of the resulting systems were also determined. Results obtained from elemental analysis and by the Bradford method enabled the determination of optimum parameters for the immobilization process. Based on the hydrolysis reaction of para-nitrophenyl palmitate, a determination was made of the catalytic activity, thermal and pH stability, and reusability. The systems with immobilized enzymes were found to have a hydrolytic activity of 5.72 mU, and increased thermal and pH stability compared with the native lipase. The products were also shown to retain approximately 80% of their initial catalytic activity, even after 20 reaction cycles. The immobilization process, using a cheap, non-toxic matrix of natural origin, leads to systems with potential applications in wastewater remediation processes and in biosensors.

Kraft lignin/silica-AgNPs as a functional material with antibacterial activity.

Advanced functional silica/lignin hybrid materials, modified with nanosilver, were obtained. The commercial silica Syloid 244 was used, modified with N-(2-aminoethyl)-3-aminopropyltrimethoxysilane to increase its chemical affinity to lignin. Similarly, kraft lignin was oxidized using a solution of sodium periodate to activate appropriate functional groups on its surface. Silver nanoparticles were grafted onto the resulting silica/lignin hybrids. The systems obtained were comprehensively tested using available techniques and methods, including transmission electron microscopy, Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, elemental analysis and atomic absorption spectroscopy. An evaluation was also made of the electrokinetic stability of the systems with and without silver nanoparticles. Conclusions were drawn concerning the chemical nature of the bonds between the precursors and the effectiveness of the method of binding nanosilver to the hybrid materials. The antimicrobial activity of the studied materials was tested against five species of Gram-positive and Gram-negative bacteria. The addition of silver nanoparticles to the silica/lignin hybrids led to inhibition of the growth of the analyzed bacteria. The best results were obtained against Pseudomonas aeruginosa, a dangerous human pathogen.

Synthesis of nanostructured chitin–hematite composites under extreme biomimetic conditions

Chitin of poriferan origin is a unique and thermostable biological material. It also represents an example of a renewable materials source due to the high regeneration ability of Aplysina sponges under marine ranching conditions. Chitinous scaffolds isolated from the skeleton of the marine sponge Aplysina aerophoba were used as a template for the in vitro formation of Fe2O3 under conditions (pH ∼ 1.5, 90 °C) which are extreme for biological materials. Novel chitin–Fe2O3 three dimensional composites, which have been prepared for the first time using hydrothermal synthesis, were thoroughly characterized using numerous analytical methods including Raman spectroscopy, XPS, XRD, electron diffraction and HR-TEM. We demonstrate the growth of uniform Fe2O3 nanocrystals into the nanostructured chitin substrate and propose a possible mechanism of chitin–hematite interactions. Moreover, we show that composites made of sponge chitin–Fe2O3 hybrid materials with active carbon can be successfully used as electrode materials for electrochemical capacitors.

The sol–gel approach as a method of synthesis of xMgO·ySiO2 powder with defined physicochemical properties including crystalline structure

The physicochemical properties of synthetic powders depend strongly on the method of their preparation. The present work concerns the use of the sol–gel method to prepare xMgO·ySiO2 powders with defined physicochemical and structural properties. An important objective was to determine how the basic process parameters (including the type and concentration of the reactants) influence the physicochemical properties of the resulting material. To obtain a synthetic powders, organic precursors of magnesium (magnesium ethoxide), and silicon (tetraethoxysilane) were used. Selected products were subjected to calcination to identify the crystalline structure of the powders and to determine the impact of the proposed method of preparation on this parameter. This aspect of the research will significantly improve the range of application of the manufactured products. The powders obtained by the proposed method were thoroughly analyzed in terms of chemical composition, crystalline structure, morphology and nature of dispersion, parameters of porous structure, and thermal as well as electrokinetic properties. The sol–gel process proved very effective in the synthesis of highly active powders, as evidenced by the very high values obtained for the products’ surface area. It was also confirmed that the physicochemical parameters are strongly dependent on the mass ratio of the reactants and on the method of final treatment of the precipitates.

Silica/lignosulfonate hybrid materials: Preparation and characterization

The research reported here concerns the synthesis, characterization and potential applications of silica/lignosulfonate hybrid materials. Three types of silica were used (Aerosil®200, Syloid®244 and hydrated silica), along with magnesium lignosulfonate. The effectiveness of the hybrid material synthesis methodology was confirmed indirectly, using Fourier transform infrared spectroscopy, elemental and colorimetric analysis. Dispersive-morphological analysis indicates that the products with the best properties were obtained using 10 parts by weight of magnesium lignosulfonate per 100 parts of Syloid®244 silica. The relatively high thermal stability recorded for the majority of the synthesized products indicates the potential use of this kind of a material as a polymer filler. Results indicating the high electrokinetic stability of the materials are also of great importance. Additionally, the very good porous structure properties indicate the potential use of silica/lignosulfonate systems as biosorbents of hazardous metal ions and harmful organic compounds.

Adsorption of C.I. Natural Red 4 onto Spongin Skeleton of Marine Demosponge

C.I. Natural Red 4 dye, also known as carmine or cochineal, was adsorbed onto the surface of spongin-based fibrous skeleton of Hippospongia communis marine demosponge for the first time. The influence of the initial concentration of dye, the contact time, and the pH of the solution on the adsorption process was investigated. The results presented here confirm the effectiveness of the proposed method for developing a novel dye/biopolymer hybrid material. The kinetics of the adsorption of carmine onto a marine sponge were also determined. The experimental data correspond directly to a pseudo-second-order model for adsorption kinetics (r2 = 0.979–0.999). The hybrid product was subjected to various types of analysis (FT-IR, Raman, 13C CP/MAS NMR, XPS) to investigate the nature of the interactions between the spongin (adsorbent) and the dye (the adsorbate). The dominant interactions between the dye and spongin were found to be hydrogen bonds and electrostatic effects. Combining the dye with a spongin support resulted with a novel hybrid material that is potentially attractive for bioactive applications and drug delivery systems.

Titania/lignin hybrid materials as a novel support for α-amylase immobilization: A comprehensive study

α-Amylase from Aspergillus oryzae was immobilized via covalent bonds and by physical interactions on a synthesized titania/lignin novel hybrid support. A temperature of 5°C, a pH of 7.0, an initial enzyme solution concentration of 3.0mg/mL and a 3h process duration were found to be optimal for the highest activity of the immobilized enzyme. Moreover, the effect of temperature, pH, storage time and repeated catalytic cycles on the activity of free and immobilized enzyme was examined. Bound α-amylase showed enhanced thermal and chemical stability, and its reusability was also improved. Immobilized α-amylase retained over 80% of its initial activity when stored for 30days at 4°C. Kinetic parameters of the free and immobilized biocatalyst were calculated and compared. The maximum reaction rate (Vmax) and turnover number (kcat) were slightly lower for the immobilized enzyme than for the free enzyme. It should be clearly stated that this work presents a useful protocol to produce stable and active immobilized α-amylase onto titania/lignin hybrid which may also be applied to immobilization of other enzymes.

Luffa cylindrica sponges as a thermally and chemically stable support for Aspergillus niger lipase

The use of biopolymer compounds as matrices for enzyme immobilization is currently a focus of increasing interest. In the present work we propose the use of Luffa cylindrica vegetable sponges as a support for the lipase extracted from Aspergillus niger. Effectiveness of immobilization was analyzed using Fourier transform infrared spectroscopy, elemental analysis and the Bradford method. An initial enzyme solution concentration of 1.0 mg/mL and an immobilization time of 12 h were selected as the parameters that produce a system retaining the highest hydrolytic activity (84% of free enzyme). The resulting biocatalyst system also exhibited high thermal and chemical stability, reusability and storage stability, which makes it a candidate for use in a wide range of applications. Kinetic parameters for the native and immobilized lipase were also calculated. The value of the Michaelis–Menten constant for the immobilized lipase (0.47 mM) is higher than for the free enzyme (0.21 mM), which indicates that the adsorbed enzyme exhibits a lower affinity to the substrate than native lipase.

Immobilization of Amano Lipase A onto Stöber silica surface: process characterization and kinetic studies

Abstract The immobilization of Amano Lipase A from Aspergillus niger by adsorption onto Stöber silica matrix obtained by sol-gel method was studied. The effectiveness of the enzyme immobilization and thus the usefulness of the method was demonstrated by a number of physicochemical analysis techniques including Fourier Transform Infrared Spectroscopy (FT-IR), elemental analysis (EA), thermogravimetric analysis (TG), porous structure of the support and the products after immobilization from the enzyme solution with various concentration at different times. The analysis of the process’ kinetics allowed the determination of the sorption parameters of the support and optimization of the process. The optimum initial concentration of the enzyme solution was found to be 5 mg mL-1, while the optimum time of the immobilization was 120 minutes. These values of the variable parameters of the process were obtained by as ensuring the immobilization of the largest possible amount of the biocatalyst at Graphical Abstract