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Egzopolisacharydy bakteryjne : budowa i funkcje

Samaszko-Fiertek J., Kuźma M., Dmochowska B., Ślusarz R., Madaj J.

Wiadomości Chemiczne

2016

[Z] 70, 7-8

473--496

Exopolysaccharides fulfil protective functions and allow bacteria live in the communities, single or mixed, by facilitating adhesion to surfaces and to each other. Microbes prefer to exist in the form of a biofilm. The term biofilm was introduced in 1978 and is the group of microorganisms surrounded by extracellular, highly hydrated mucus, which allows adhesion on various surfaces and adhesion of cells to each other [1]. The extracellular slime owes its character mainly due to the presence of exopolysaccharides. Bacteria living in biofilms, have a high resistance to external factors, such as changes in temperature, pH, humidity, oxygenation, presence of bacteriocins, antibodies or antibiotics. They may be up to 1,000 times more resistant to antibiotics than planktonic forms. They can be synthesized inside and outside bacteria cell. The structure of the bacterial exopolysaccharide is very diverse, but very often, due to the presence of uronic acid residues, or non-sugar organic acids as pyruvic acid, succinic acid, as well as residues of inorganic acids such as phosphoric acid or sulfuric acid, they are negatively charged particles. In addition, a characteristic of most of the exopolysaccharides (EPS) is their enormous molecular mass of up to several million g/mol [11]. Thanks to its rheological properties, ease of isolation, and often biodegradable antioxidant activity extracellular polysaccharides are increasingly used in industry as a gelling agents, hardening and thickening agents, emulsifiers, food coatings and pharmaceutical products. In addition, they can be used as bandages, anti-cancer agents, cholesterol-lowering, antiulcer or immunomodulators [20–27]. This article discusses in details the selected exopolysaccharides such as xanthan, gellan, exopolysaccharides of lactic acid bacteria, dextran, bacterial cellulose, alginic acid, hyaluronic acid, mannans.

Polymer-metal complexes based on gellan

Vasiliu S., Racovita S., Neagu V., Popa M., Desbrieres J.

Polimery

2010

T. 55, nr 11-12

839-845

By dropwise adding solutions of gellan (Gil) or gellan + poly(vinyl alcohol) (PVAL) mixture into different metal salt solutions - FeCl3 · 6 H2O, FeCl2 · 4 H2O, CoCl2 · 6 H2O, CuCl2 · 2 H2O - at 30 °C under constant stirring, preparation of spherical microparticles based on polymer-metal complexes has been performed. FT-IR spectroscopy, TGA analysis and swelling measurements of these microparticles in water showed the influence of the metal type ions on their structure, thermal stability and water swelling capacity. The FT-IR spectroscopy allows to explain the mechanism of polymer-metal complexes formation and the optical microscopy showed that the microparticles obtained had good sphericity with average diameter ranging from 719 μm to 830 μm. The thermal stability of the polymer-metal complexes was found to be higher than that of the gellan.

Opisano prosty i łatwy do zrealizowania sposób otrzymania w temp. 30 °C kompleksów gelanu (Gll - anionowy, wielkocząsteczkowy, dezaktywowany polisacharyd pochodzenia naturalnego) lub mieszanin Gil + poli(alkohol winylowy) (PVAL) z wodzianami różnych soli metali (FeCl3, FeCl2, CuCl2, CoCl2) (rys. l, tabela 1). Kompleksy mają postać regularnych okrągłych mikrocząstek o wymiarach 719-830 μm. Na podstawie widm IR (rys. 2 i 3, tabela 2) zinterpretowano mechanizm powstawania kompleksów i określono ich budowę. Zbadano termostabilność kompleksów oraz kinetykę ich degradacji cieplnej (rys. 4, tabela 3); jest to wieloetapowy proces o skomplikowanym przebiegu. Scharakteryzowano zjawisko pęcznienia kompleksów w wodzie w temp. 25 °C (rys. 5, tabela 4) ustalając następującą zależność stopnia spęcznienia od rodzaju zawartego w nich metalu: Fe³+ < Fe²+ < Cu²+ < Co²+.