Polysaccharides coacervation

Turgeon, S.L., Schmitt, C., Sanchez, C. (2007). Protein-polysaccharide complexes and coacervates. Current Opinion in Colloid and Interface Science, 12, 166-178. 

The electrostatic interaction between oppositely charged protein and polysaccharide can be utilized for encapsulation and delivery of hydro-phobic nutraceuticals. As a result of this interaction, we may have either complex coacervation (and precipitation) or soluble complex formation, depending on various factors, such as the type of polysaccharide used (anionic/cationic), the solution pH, the ionic strength, and the ratio of polysaccharide to protein (see sections 2.1, 2.2 and 2.5 in chapter seven for more details) (Schmitt et al, 1998 de Kruif et al., 2004 Livney, 2008 McClements et al, 2008, 2009). The phenomenon of complex... 

There is mobility of both the protein and the polysaccharide in the liquid coacervate phase, i.e., the coacervate structure is dynamic, with enormous time-scale variations from milliseconds to several days (or even longer in precipitates). 

If the polysaccharide is a strong polyelectrolyte, then precipitation occurs instead of coacervation. 

At the mixing ratio where coacervation is maximized, the protein-polysaccharide complexes are electrically neutral. 

Polymers may be induced to encapsulate other molecules by a variety of means (Risch and Reineccius, 1995) as diverse as dipping, spray-drying, extrusion, evaporation, and coacervation each technique has its special applications, strengths, and weaknesses. Advantages in common are the protection and slow release of the encapsulate. In any of the mechanisms, a coagulable polymer precipitates around a core of labile material. Polysaccharides are regular encapsulating polymers (Risch and Reineccius, 1995) acacia gum is particularly efficacious because of its protein content. 

In a microencapsulation method, the encapsulate—usually an oil, flavor, enzyme, or medicinal—is emulsified in a dilute aqueous gelatin sol, a polysaccharide is added, and conditions are adjusted to favor coacervation. The encapsulate should not be truly soluble in the solvent or the cosolutes and the cosolutes should be differentially soluble in the liquid solvent. As much as 60-98% of the labile substance may be harvested by microencapsulation to yield microcapsules in the form of a free-flowing powder (Sirine, 1968). 

Clostridium welchii, enzymes, effect on blood group substances, IV, 55 Coacervation, I, 277 Coatings, cellulose ester, I, 323 Co-carboxylase, II, 124 Coccidioides immitis, polysaccharide formed by, II, 225 Cocositol, III, 60 Coir, xylan peroentage in, V, 271 Collagenaae, effect on blood group substances, IV, 55... 

Kruif, C.G. de., Weinbreck, F., and Vries, R. de (2004). Complex coacervation of proteins and anionic polysaccharides. Curr. Opin. Colloid Interface Sci. 9, 340-349. 

Watase, M., Nishinari, K., Clark, A. H., and Ross-Murphy, S. B. 1989. ESfferential scanning calorimetry, rheology. X-ray, and NMR of very corrcentrated agarose gels. Macromolecules 22 1196-1201. Weinbreck, F. 2004. Whey protein/Polysaccharide Coacervates Structure and Dynamics. Ph.D thesis, Utrecht University, The Netherlands. 

Proteinoids produced in laboratories can cluster together into droplets that separate, and that may protect their components from degrading influences of the surrounding environment. These droplets are like extremely simple cells, although they can not reproduce. Such droplets are called microspheres. When fats (i.e., lipids) are present, the microspheres that form are even more cell-like. If a mixture of linked amino acids called polypeptides, sugars called polysaccharides, and nucleic acids is shaken, droplets called coacervates will form. All of these kinds of droplets are called protobionts, and they may represent a stage in the genesis of cellular life. 

Coacervates—cluster of polysaccharides, nucleic acids, and polypeptides formed when a solution of these molecules is shaken. Coacervates are a type of protobiont. 

Coacervation or coprecipitation of host and guest and suspension of the guest molecule in polysaccharide gels, followed by drying, is another common procedure. Microcapsules can be made on the formation of polysaccharide-protein complexes in the presence of a potential host. Preswelled granular starches are potential natural microcapsules (Lii et al., 2001b). 

A survey of the abundant literature shows clearly that pH, ionic strength, type of ions, protein to polysaccharide ratio, size, shape, charge density and flexibility of macromolecules are important parameters controlling the extent of phase separation as determined at equilibrium.3,4,6-10 On the contrary, out of equilibrium conditions have attracted much less attention. Some important questions such as the transition from macromolecular complexes/aggregates to the appearance of coacervates, the structure of coacervates and the phase ordering kinetics... 

In the forementioned laboratories, we started with a new strategy based on phase separation in order to prepare natural particles. Simple or complex coacervation methods involving proteins or protein and polysaccharide mixtures3 were used to create new matrices dedicated to controlled release applications. The colloidal carriers produced were in the micrometre or nanometre size range depending on the substrates or the methods used. Wheat proteins, gliadins, were implicated in simple coacervation to produce nanospheres. Controlled release experiments with model compounds were conducted in order to evaluate... 

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