Polysaccharides stickiness

Many microbial infections and toxins are spread by biofilms. Biofilm formation occurs on virtually every surface, starting with the adhesion of planctonic cells or small dispersed biofilm fragments. Proliferation of the cells is accompanied by the expression of an extracellular polysaccharide-based matrix [6], The cells embedded in this matrix are well protected and up to 1000 times less susceptible to antibiotics [7], Once a biofilm is formed, it is extremely difficult to remove this contamination. Thus, all antimicrobial surfaces should prevent the primary attack [8], One class of antimicrobial surfaces prevents the primary attack by creating surfaces that are not sticky to microbial cells, i.e., they do not allow adhesion of these cells. The other major class of antimicrobial surfaces is based on the killing of approaching microbes (see Fig. 2). Interestingly, both approaches can be achieved either by permanent surface modifications or by releasing bioactive compounds. 

P. jahnii Zingone (Fig. 5e) forms colonies very different from all other Phaeocystis colonies (Zingone et al. 1999). These are loose aggregates of non-motile cells embedded in a sticky mucilaginous matrix probably of polysaccharide nature, with no external layer nor a definite shape. In culture material the colonies may form wide sheets with margins at times sticking to the cell tube. Colonial cells range from 6 to 8.5 gm and have 2-4 chloroplasts. 

Bacterial Polysaccharides. Many bacterial species release exopolysaccharides into their environment. The synthesis of capsular and slime polysaccharides or similar sticky surface materials serves as an adhesive to attach the bacteria to solid substrates, even in a marine environment. These polysaccharides range from compositionally simple homopolymers to very complex heteropolymers composed of several individual sugars linked in a variety of ways. 

The above equation was also applicable to stickiness, S, substituted in place of the thickness, T. Because Cutler et al. (1983) have shown that perceived thickness and viscosity were linearly related, the correlations for perceived thickness can be used for perceived viscosity. By combining Equations 7.1 and 7.3, one obtain an expression to calculate the viscosity 7n of aNev nonian liquid that would be perceived as having an identical thickness and stickiness to any polysaccharide dispersion with known and ]>o.i ... 

The glass transition processes in foods may result from a rapid removal of water from solids. Based on that, e.g., the Tg values of anhydrous polysaccharides are high, and the food materials may decompose at temperatures below Tg (Kokini et al 1994 Roos and Karel, 1991b). The glass temperature transition affects viscosity, stickiness, crispness, collapse, crystallization, and ice formation, and can strongly influence deteriorative reaction rates. This provides a new theoretical and experimental framework for the study of food systems to unify structural and functional aspects of foods, described in terms of water dynamics and glass dynamics. 

They can also be obtained from the hydrolysis of starch with dilute acid at low temperature. Dextrins are mixtures of polysaccharides having 5-15 glucose units in their structure. They are sticky, sweet substances used in the manufacture of adhesives and soft drinks. 

Moreover, plant cells in continuous suspension culture have some characteristics that complicate the process. Plant cells tend to growth in aggregates and excrete sticky and viscosity-increasing polysaccharides, which make it... 

Acetobacter xylinum produces two forms of cellulose (1) cellulose I, the rib-bon-like polymer, and (2) cellulose II, the thermodynamically more stable amorphous polymer [9]. They can be divided according to their morphological localization as intracellular polysaccharides located inside, or as part of the cytoplasmic membrane cell wall polysaccharides forming a structural part of the cell wall and extracellular polysaccharides located outside the cell wall. Extracellular polysaccharides occur in two forms loose slime, which is non-adherent to the cell and imparts a sticky consistency to bacterial growth on a solid medium or an increased viscosity in a liquid medium and microcapsules or capsules, which adhere to the ceU wall. 

Sutherland LA sticky business. Microbial polysaccharides current products and future trends. Microbiol... 

When a plant is wounded there often exudes from the opening a viscous, sticky fluid which tends to cover and seal the incision. On drying in air the fluid thickens and hardens to a brittle, translucent, glassy mass. These exu-udates, plant gums, are in deciduous plants, often composed of polysaccharides. They are practically always highly branched structures (D in Fig. 1) composed of two to five types of monosaccharides. Almost all exu-... 

Capsules. They are a protective structure, which may be produced by some bacteria. Capsules consist of polysaccharide, polypeptide or both and are firmly attached to the cell wall. It is thought that the presence of a capsule protects the cell from phagocytosis (being eaten) although the mechanism is not known. The capsule can prevent from dehydration and trap nutrients. Also, the sticky nature of the capsule aids in the attachment of the bacteria to surfaces. The significance of capsules in papermaking systems is not known. 

The tendency of branched polysaccharides to coagulation is very low. At high concentrations they form sticky pastes, which is probably due to interactions of side chains. After drying, these substances can easily re-hydrate. 

Mucilages—Presently, these substances are usually classified under gums, since they have many of the same properties. Formerly, mucilages were considered to be the plant polysaccharides which readily formed sticky, slimy (muci-lagenous) solutions in water. Two of the most familiar examples of these substances are those that may be extracted from flax seeds and psyllium seeds. Various products made from these seeds nave long been used as laxatives. It is noteworthy that ladies used to set their hair in curls or waves with a solution obtained by steeping flax seeds in hot water. 

As technically employed in industry, the term gum usually refers to polysaccharides (long chains of simple sugars) or their derivatives, which are dispersible in either hot or cold water to produce viscous mixtures. Gums also may include water-soluble derivatives of cellulose and modifications of other polysaccharides which in their natural form are insoluble. The original definition of gums applied only to the sticky gummy natural plant exudates. 

Over a long period polysaccharides have been used as gums, for example modified-starch, wallpaper pastes. The stickiness of a polysaccharide is governed by the size and shape of the molecule, the most effective being... 

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