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Poly(vinyl alcohol) (PVA) was modified with 3-aminopropyltriethoxysilane and was used for synthesis of poly(urethane-urea) microcapsules (PUUMc) with encapsulated maltogenic a-amylase (BaMa) (E. C. 3.2.1.133). The optimization of PVA modification factors and PUUMc synthesis conditions was performed. Chemical structure, porosity and thermostability of PUUMc which were obtained under various synthesis conditions were evaluated. Release rate of BaMa from PUUMc was slower and EI of BaMa was higher, when enzyme was encapsulated during PUUMc synthesis.

Preparation of polyurethane microparticles (PU) modified with gold (Au-NPs) or silver nanoparticles (Ag-NPs) for maltogenase immobilization was presented. The PU/Au-NPs and PU/Ag-NPs conjugates were prepared via adsorption of already synthesized nanoparticles on PU or via synthesis of nanoparticles within bulk of PU. Au-NPs of different size and Ag-NPs, synthesized by reduction of tetrachloroauric acid and silver nitrate with sodium citrate, were characterized by UV–vis and Dynamic Light Scattering technique. The best results (immobilization yield 90.0% and efficiency 83.5%) were achieved, when maltogenase was immobilized onto PU modified with Au-NPs(13nm) by adsorption method. Immobilized maltogenase was stable in time, after 25 days of storage 95.2-98.6% of initial enzyme activity was remained. Moreover, the results revealed that stability of enzyme was improved upon immobilization on PU/Au-NPs(13nm) in comparison to PU without Au-NPs. Enhancement of photoluminescence after enzyme immobilization confirmed the successful attachment of maltogenase to PU/Au-NPs or PU/Ag-NPs via metal nanoparticles.

The immobilization of maltogenic α-amylase from Bacillus stearothermophilus (BsMa) onto novel porous poly(urethane urea) (PUU) microparticles synthesized from poly(vinyl alcohol) and isophorone diisocyanate was performed by covalent attachment to free isocyanate groups from PUU microparticles, or by physical adsorption of enzyme onto the surface of the carrier. The influence of structure, surface area and porosity of microparticles on the catalytic properties of immobilized BsMa was evaluated. The highest efficiency of immobilization of BsMa was found to be 72%. Optimal activity of immobilized BsMa was found to have increased by 10°C compared with the native enzyme. Influence of concentration of sodium chloride on activity of immobilized BsMa was evaluated. High storage and thermal stability and reusability for starch hydrolysis of immobilized enzyme were obtained. Immobilized BsMa has a great potential for biotechnology.

Polysaccharide-based nanocomplexes, intended for simultaneous encapsulation and controlled release of 5-Fluorouracil (5-FU) and Temozolomide (TMZ) were developed via the complexation method using chitosan, alginic and polygalacturonic acid. Investigation focused on the influence of polysaccharides on the properties of the system and amelioration of the stability of the drugs, in particular TMZ. The dimensions of particles and their ζ-potential were found to range between 100 and 200nm and -25 to +40mV, respectively. Encapsulation efficiency varied from 16% to over 70%, depending on the given system. The influence of pH on the release and co-release of TMZ and 5-FU was evaluated under different pH conditions. The stability of the loaded drug, in particular TMZ, after release was evaluated and confirmed by LC-MS analysis. Results suggested that the amount of loaded drug(s) and the release rate is connected with the weight ratio of polysaccharides and the pH of the media. One-way ANOVA analysis on the obtained data revealed no interference between the drugs during the encapsulation and release process, and in particular no hydrolysis of TMZ occurred suggesting that CS-ALG and CS-PGA would represent interesting carriers for multi-drug controlled release and drugs protection.

Nisin is a small cationic peptide composed of 34 amino acid residues. It exhibits a wide spectrum antimicrobial activity against Gram-positive bacteria and is suitable for food preservation. In order to protect nisin from the interaction with food components and to ensure the stability of antimicrobial peptide during food processing and storage period, the preparation of nisin-loaded pectin nanoparticles in the simple and low cost way based on the complexation method is presented. Three types of pectin biopolymer were tested and found that the methoxylation degree of pectin influenced on the nisin loading efficiency and particle size. For the complex formation, both electrostatic and hydrophobic interactions were important. Nisin-loaded pectin nanoparticles exhibited antimicrobial activity dependent on the type of biopolymer. In view of particle size and antimicrobial activity, nisin-loaded pectic acid nanoparticles were identified as the most suitable and perspective to be used in food industry as an anti-microbial system.

The PU/Au-NPs conjugates based on poly(vinyl alcohol)-containing polyurethane microparticles coated with Au-NPs are prepared by a heat-treated method. The PU/Au-NPs conjugates are characterized by FT-IR , SEM, TEM analysis. The appearance of characteristic peaks in the FT-IR spectra at 1574 and 1624 cm − 1 , which are attributed to urethane groups, are presented for both PU and PU/Au-NPs conjugate. The absorption band at 1716–1718 cm − 1 , attributed to the hydrogen-bonded urethane carbonyl groups of PU/Au-NPs (13nm) -A is higher than that obtained for unmodifi ed PU. The Au-NPs (13nm) are found to be well dispersed in the PU. The Au-NPs (3.5nm) tend toward agglomeration when they are entrapped within PU. It is determined, that Au-NPs present in PU-Au conjugates quench the luminescence of PU.

A series of porous polyurethane (PU) microparticles from poly(vinyl alcohol) (PVA) and hexamethylene diisocyanate (HMDI) using different ratios of components were obtained by one step method. Molar compositions of PU microparticles were estimated by determination of nitrogen, isocyanate and hydroxyl groups. PU carriers which were synthesized using optimal initial molar ratios of PVA and HMDI were applied for immobilization of maltogenase (MG) from Bacillus stearothermophilus . Immobilized enzyme exhibited higher catalytic activity and enhanced temperature stability in comparison with the native MG. Maximal loading 7.78 mg/g wet carrier was reached when PU microparticles with initial molar ratio of PVA and HMDI = 1:3 was used as a carrier for immobilization. The high efficiency of immobilization (EI) was obtained using PU microparticles when initial molar ratio of HMDI and PVA was 1:1–1:10. High stability of MG immobilized onto PU microparticles during storage was demonstrated. Immobilized starch hydrolyzing enzyme was successfully tested in batch and column type reactors for hydrolysis of potato starch. MG immobilized onto PU enables easy separation from the reaction medium and reuse of the immobilized preparation over seven reaction cycles in bath operation and at least three cycles in column type reactor.

A series of polyurethane (PU) microspheres, based on 4,4′-diphenylmethane diisocyanate and 1,4-butanediol or a mixture of 1,4-butanediol and polyether glycol (M = 1400) were synthesized by a one-step method. The obtained PU microspheres were characterized by infrared spectroscopy, polarizing optical microscopy and dynamic thermogravimetry. Morphology studies of PU microspheres revealed that the material consists of spherical particles with relatively narrow particle size distribution in the range 1–100 µm and preferably between 10 to 50 µm; the obtained polymers were thermally stable up to 533–573 K. Maltogenase from Bacillus stearothermophilus was immobilized onto PU microspheres, synthesized using different ratios of components. High yield (about 100%) and efficiency (over 100%) of immobilization were obtained. Copyright © 2006 John Wiley & Sons, Ltd.

The novel poly(urethane-urea) microcapsules (PUUMC) were obtained by the interfacial polyaddition reaction between the oil-soluble hexamethylene diisocyanate (HMDI) and the water soluble poly(vinyl alcohol) (PVA) in a water-in-oil (W/O) emulsion. The PVA was used instead of diols. Maltogenase L (maltogenic α-amylase from Bacillus stearothermophilus (E. C. 3.2.1.133) (MG) was encapsulated in the PUUMC during or after formation of capsules. The PUUMC were thoroughly characterised by chemical analytical methods, FT-IR, SEM, thermal analysis, surface area, pore volume and size analysis. Furthermore, by carefully analysing the influencing factors including: catalyst and surfactants and their concentrations, the initial molar ratio of PVA and HMDI, stirring rate and ratio of dispersed phase to external phase, the optimum synthesis conditions were found out. A controlled release of MG could be observed in many cases. Delayed-release capsules were obtained when initial concentration of HMDI was increased. These capsules have potential application in biotechnology for saccharification of starch.

Alkaline phosphatase from E. coli was immobilized on Sepharose-4B, macroporous cellulose and chitosan-based carriers. The yields of immobilization were over 60% in most cases. It was shown that immobilized alkaline phosphatase can be used for dephosphorylation of DNA 5'-termini.

ß-galactosidase from Penicillium canescens was immobilized on chitosan, sepharose-4B, foamable polyurethane and some other carriers. The highest yield of immobilization (up to 98 %) was obtained by using chitosan as a carrier. The optimum pH and temperature were not significantly altered by immobilization. High stability of immobilized ß-galactosidase during storage was demonstrated. Efficient lactose saccharification (over 90 %) in whey was achieved by using immobilized ß-galactosidase. (C) Central European Science Journals. All rights reserved.

Enzymatic hydrolysis of lactose at 5°C was proposed for production of low lactose milk. Stability of milk casein particles was decreased and their dispersity was increased as a results of lactose conversion. Immobilized β-galactosidase was successfully tested for lactose hydrolysis in whey.