Artykuły (WBiNoŻ)

Stały URI dla kolekcjihttp://hdl.handle.net/11652/147

Przeglądaj

Teraz wyświetlane 1 - 4 z 4

A comparison of two enzymatic methods of clinical dextran production
(Wydawnictwo Politechniki Łódzkiej, 2017) Sikora, Barbara; Kubik, Celina; Bielecki, Stanisław
The aim of this study was to evaluate and compare of the two enzymatic methods of clinical dextran production were compared. The reactions were performed at 30°C and pH 5.4 in solutions containing different amounts of sucrose, using dextransucrase (DS, in the presence of dextranase (D) (method 1) or acceptor dextrans (method 2). The activity of Leuconostoc mesenteroides L dextransucrase (DS), which converts sucrose to dextran, was 0.4 U ml-1 in both the methods. As much as 53-56% of clinical dextran fractions were obtained for 28 h from 10% sucrose solutions, which contained 1.5% or 2.5% acceptor dextrans with molecular mass of 10 and 15 kDa, respectively. Approximately 50% of these fractions was obtained (also in 28 h) from 10% sucrose solutions by using 0.004 U ml-1 of DN, added to reaction mixtures 5 h later than Our experiments indicate that the clinical dextran can be efficiently produced by using both the compared methods, which employ either acceptor dextrans with definite molecular mass, or the dextranase. Because consumption of the latter enzyme is rather small, and it is easily available, thus this method should be attractive for clinical dextran manufacturers.
Laccases – enzymes with an unlimited potential
(Lodz University of Technology Press, 2017) Szczęsna-Antczak, Mirosława; Benedykt Kaczmarek, Michał; Kwiatos, Natalia; Bielecki, Stanisław
Laccases (EC 1.10.3.2) are among the few enzymes, the history of which dates back to the 19th century. These oxidoreductases are present in almost all known fungi, some species of higher plants and insects. Moreover, in recent years, these enzymes have also been found in some bacterial organisms. Due to their significant properties and structure of the catalytic centre, laccases have been classified as the multicopper oxidases (MCOs). These enzymes are able to catalyse the oxidation of phenolic and non-phenolic compounds, with the aid of small molecules referred to as mediators. Thanks to their diverse nature, laccases have gained attention of both scientists and entrepreneurs from all over the world. Their significance is reflected in countless scientific and industrial applications, wherein laccases have become inseparable from chemical syntheses, the food industry, textile industry, biosensor design and the environmental protection. This paper gathers the most important information and the latest scientific discoveries relating to this desirable biocatalyst.
Production of co-immobilized dextransucrase and dextranase preparations and their application in isomalto-oligosaccharides synthesis
(Wydawnictwo Politechniki Łódzkiej, 2017) Sikora, Barbara; Kubik, Celina; Bielecki, Stanisław
Dextransucrase (DS) from Leuconostoc mesenteroides and dextranase (DN) from Penicillium funiculosum were co-immobilized by entrapment in calcium alginate and used to produce isomaltooligosaccharides (IMOs) from sucrose. DS convert sucrose into dextran, which is the substrate for DN, so that IMOs are products of dextran hydrolysis. Before the co-immobilization DS was cross-linked with glutardialdehyde (GA), while DN was adsorbed on hydroxyapatite (HAp). Cross-linking was essential for the stability of DS and pre-immobilization of DN to prevent enzyme from leaking out of the alginate beads. Operational stability of co-immobilized preparations of DS and DN was estimated based on amounts of isomaltose and isomaltotriose formed during successive 24h processes of IMOs synthesis, carried out at 30oC, pH 5.4 and 200 rpm in 10% (w/v) sucrose solutions. Preparation characterized by the initial DS/DN activities ratio of 1/14 was found to maintain these activities at least 100 h of IMOs synthesis (5 repeated batch reaction).
Rola alternatywnych czynników sigma S (σS) i sigma B (σB) w odpowiedzi komórki bakteryjnej na stres oraz ich regulacja
(Polish Microbiology Society, 2014) Opęchowska, Marzena; Bielecki, Stanisław
Bacteria successfully take possession of almost every recess of the earth. However bacteria can be liable to big changes of environmental conditions in every settled biotope. Some of them living in a high specializated medium do not show usually ability of tolerate others media than their most favourable. In case of changes of medium parameters some of bacteria start to migrate and look for others media securing them proper growth and development approximate optimum conditions. There are also bacteria which are able to survive in spite of changes happen in their direct environmental. Their survival competence is caused by the lack of susceptibility on specified medium changes or ability of adaptation to new conditions moreover by taking the profits from the medium. The tolerance and adaptation bacterial cells to different conditions which following in the nearest environmental result from cells response on stress factors. Precised signals coming from the medium cause in the cells a number of changes happen in genes expression regulated on transcription and translation level. The information coded in bacterial genome enable cells to produce many different proteins. However not all proteins are synthesized in the same time and the process of their synthesis is subject to strict control. Cells under stress synthesize proteins which secure them survival in untipical for their growing conditions. The main roles in this process play alternative sigma factors. Bacterial cells contain also general sigma factor (for example σ 70 in Escherichia coli, σ 43 in Bacillus subtilis) responsible for transcription most of the genes. However alternative sigma factors rarely regulate initiation of transcription. They are active only in case of cell stress conditions and also they take part in gene expression conected with the life cycle of the cell and stationary or exponential growth phase of bacteria. The most important function in stress conditions of E. coli plays an alternative sigma S (σ S, σ38) factor. Because of its regulatory function a lot of attention is dedicated to researches refer to σS in a recent time. Sigma B – which is one of the best known alternative sigma factors in Gram positive bacteria – plays a similar role to sigma S. Factor σ B functions as a general response regulator to stress in such bacteria as Bacillus, Staphylococcus and Listeria . These two alternative sigma factors: sigma S and sigma B often, if not always work in connection with others form of regulation. Bacteria show ability of detection many signals coming from the environment by means of sensors systems situated in cell envelope. Although σ S and σ B play the similar role in the cell they are controlled by completely different mechanisms.