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The extensive use of antibiotics leads to an increasing number of antibiotic-resistant pathogenic microorganisms. The development of new antimicrobials is needed for clinical, veterinary, and food applications. Bacteriocins are small peptides with antimicrobial activity ribosomally synthesized by bacteria and could be applied as an alternative to classical antibiotics. In this study, the bacteriocin-like (BLIS) peptide, produced by Staphylococcus xylosus was partially purified and main characteristics (pH, thermal stability, resistance to some protease enzymes and molecular weight) were evaluated. Ammonium sulfate precipitation, acetone extraction and ion-exchange chromatography methods were applied for purification of bacteriocin. The activity of bacteriocin was detected using a well diffusion assay method and the amount of protein concentration was estimated by Lowry method. Molecular weight (~ 6 kDa) of purified bacteriocin was determined by sodium dodecyl sulphate polyacrilamide gel electrophoresis (SDS PAGE) method. The highest purification yield (80 %) was obtained using ion-exange chromatography and SP-sepharose as sorbent. The purified bacteriocin remained stable at pH values between 2.0 and 12.0 for 4 h. No decrease in antibacterial activity was estimated after 30 min at 121º C temperature. The purified bacteriocin was resistant to papain, pepsin and trypsin action. The BLIS inhibits a growth of Listeria monocytogenes (93 ± 3.0 %), Bacillus subtilis (85 ± 4.0 %), Pediococcus pentosaceus (79 ± 4.0 %), Staphylococcus aureus (51 ± 5.0 %) and Propionibacterium acnes (70 ± 5 %) up to 24 hours. Such bacteriocin preparation could be applied as antimicrobial agent in medical and food industry.

Three new, water-soluble, N-modified chitosan derivatives containing poly(ethylene glycol), dextran or inulin side chains were used as spacers for enzyme immobilization on a natural silk carrier. Amylolytic enzymes Maltogenase L and Promozyme D2, lipolytic enzyme Resinase HT and a complex of proteolytic enzymes from Streptomyces flavus 197 were immobilized. The activity of the immobilized enzymes and their stability during storage were similar to that obtained with synthetic polyamine—poly(ethylene imine) as a spacer. High operational stability of co-immobilized amylolytic enzymes Maltogenase L and Promozyme D2 in a continuous flow mini-reactor was demonstrated.

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.

* Corresponding author. E-mail: birute@ibt.lt Lipases of different origin were screened for substrates and different reactions from the practical approach to search for the optimal conditions for biodiesel component production. The commercial lipases under analysis were shown to be specific to p-nitrophenyl fatty acid esters of medium chain length, although Lipolase100 LEX also showed a relatively high hydrolytic activity on p-nitrophenyl palmitate. The soluble Enterobacter aerogenes lipase was shown also to be the most active when hydrolysing medium-chain-length p-nitrophenyl fatty acid esters. The specificity of immobilized commercial lipases did not change as compared with soluble analogues. The immobilized Enterobacter aerogenes lipase showed no significant differences of activity towards p-nitrophenyl butyrate and medium-chain p-nitrophenyl fatty acid esters versus the attached enzyme on polyurethane and chitosan and also showed the highest hydrolytic activity on p-nitrophenyl caprylate as for soluble lipase. Enterobacter aerogenes lipase-catalyzed esterification of oleic acid with oleoyl alcohol was a long-lasting process still in progress after 91 hours. The lipase showed the highest catalytic activity when esterifying oleic acid with ethanol and 1.2-ethanediol. The enzyme slightly esterified the acid with 1.3-propanediol and was almost inactive for esterification with 2-hydroxyethyl ether. Enterobacter aerogenes lipase more efficiently hydrolysed camelina oil than rapeseed oil, considering the former to be an alternative source to be converted into biodiesel components. Methanolysis of rapeseed oil catalyzed by the lipase adsorbed on chitin was also a long-lasting process still in progress during 124 hours. The optimal glycerol-tricaprylate-to-methanol ratio was 1 : 1 for methanolysis of the substrate catalysed by Resinase HT lipase immobilized on a polyurethane support. The lipase was completely depressed at the ratio 1 : 3.

The guanidine-hydrochloride (Gdn-HCl) and thermally induced unfolding of Hsp70 from Meiothermus ruber (Mru.Hsp70) were analysed using tryptophan fluorescence and 8-anilino-1-naphthalenesulfonic acid (ANS) binding. The ANS binding to Mru.Hsp70 showed both the increase in fluorescence intensity and a shift in emission maximum. Analysis of the unfolding profile of Mru.Hsp70 indicated that Gdn-HCl induced unfolding of Mru.Hsp70 occurred through intermediate species. The tryptophan and ANS fluorescence emission spectra revealed that ATP induced conformational change increased the thermal stability of Mru.Hsp70. The data obtained are similar to those of Escherichia coli DnaK. The ATP-ase activity of chaperones is fundamental for their biological activity. It this paper we demonstrate that, in contrast to Thermus thermophilus, both Mru.Hsp40 and Mru.Hsp22 co-chaperones affect the ATP-ase activity of Mru.Hsp70. The use of truncated Mru.Hsp40 proteins showed that full-length Mru.Hsp40 is required for stimulation o...

The kinetics of the nucleophilic addition reactions of divinyl sulfone to amino groups of glycine and model proteins was studied in aqueous solution at 30°C. The rate constants for glycine, bovine serum albumin, and α1-casein were (4.84 ± 0.58) × 10–1, (2.97 ± 0.31) × 10–2, and (2.38 ± 0.49) × 10–2 M–1 s–1, respectively. Divinyl sulfone was proposed as a crosslinking reagent for the qualitative detection of protein association in solution. The crosslinking capacity of divinyl sulfone was compared to that of 1,3,5-triacryloylhexahydro-s-triazine.

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.

Zn(2+) and Co(2+) ions are known to promote human growth hormone reversible dimerization. In these studies, dimerization was also shown to be initiated by nine other metal ions: Cd(2+), Hg(2+), Cu(2+), Ag+, Au(3+), Au+, Pd(2+), Ni(2+), and Pt(4+). In some cases (Hg(2+), Ag(+), Au(3+), and Ni(2+)) formation of higher oligomers also took place. In addition further detailed investigation of dimerization in the presence of Zn(2+) ions was carried out.

Alcohol oxidase (AO) from the methylotropic yeast Pichia pastoris was isolated and investigated. Wide substrate specificity is characteristic for this enzyme. Unbranched primary alcohols are effectively oxidized by AO to aldehydes, including propargyl alcohol, 2-chloroethanol, 2-cyanoethanol, leading to important synthetic intermediates. AO was immobilized by covalent linking to macroporous cellulose activated by glutaraldehyde, yield of immobilization 80%. Presence of two izoenzymes of AO was suggested from the pH activity dependence.

About 14 proteins were tested for specific oxidative scission catalyzed by metal ions in the presence of ascorbate and oxidizing agents (O(2) or hydrogen peroxide). Only four of them were degraded by Fe(3+)/Fe(2+)- ascorbate, twelve - by Cu(2+)/Cu(+)-ascorbate and two proteins (alpha- and beta-caseins) were degraded by Pd(2+) ions. The rate and the intensity of degradation are very different for various proteins. For the most of tested proteins only a small fraction of molecules was degraded. None of them was degraded completely. Two possible reasons of protein stability against oxidative degradation may be proposed as follows: either there is no metal binding site in a protein molecule, or metal binding ligands of protein undergo a rapid oxidative modification and the metal ion is released from the binding site. Human growth hormone was cut specifically at two sites by Cu(2+)/Cu(+)-ascorbate system. At least one of amino acid residues of this protein was modified by formation of reactive carbonyl.

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.

Six difunctional and trifunctional derivatives of acrylamide were synthesized and investigated as potential protein lysine residue cross-linking agents. 1,3,5-Triacryloyl-hexahydro-s-triazine (TAT) was considered the best. The rate constants for the reactions of TAT with model nucleophiles in water solution at 25 degreesC were with the glycine anion amino group, 7.69 x 10(-3) M-1 s-1; with the anionic form of the N-acetyl-L-cysteine thiol group, 5.54 M-1 s-1; and with the Nalpha-acetyl-L-histidine imidazole ring, 1.19 x 10(-5) M-1 s-1 (at pH 9.0). The kinetics of modification of amino groups by TAT were studied for several proteins: alpha1-casein, bovine serum albumin, recombinant human growth hormone, recombinant human interferons-alpha2b, and -gamma. The results indicate that if proteins are associated into oligomeric structures in water, their subunits are effectively cross-linked by TAT.