Polysaccharides nature

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. 

J. R. Turvey and D. A. Rees, Isolation of L-galactose 6-sulphate from a seaweed polysaccharide, Nature, 189 (1961) 831-832. 

Polysaccharides Natural Enzymatic reactions Pullulans (soluble in water), dextrans (soluble in water)... 

It is clear that green polymers, as defined by their biodegradability, are almost exclusively biopolymers. The major classes of biopolymer of interest here are proteins and polysaccharides, naturally occurring biopolymers, and these are subdivided into various sub-classes, with different applications, as described above. Other polymers of interest are the bacterial polyesters and polylactides. All of these polymers have the potential to be processed into new materials, but clearly not all of these will have either attractive properties or be economically viable materials. 

Fucan is a sulfated polysaccharide, naturally present in algae such as Fucus vesiculosus or Ascophyllum nodosum. Fucan is a general name for a mixture of three polysaccharides, and among them, fucoidan (or homofucan) can be theoretically considered as an homopolymer of a-1,2 L-fucose-4-sulfate and has been studied as a ligand in the same way as fucan himself. Their interaction with two proteins implicated in the coagulation process (thrombin and antithrombin) has been studied and is at least partially ionic. However, the dissociation of the complex fucan-antithrombin seems to include a slower step which could be attributed to a conformation change of the fucan [18]. 

Contrary to microbial flavour generation directly in the food by starter cultures, the technical bioreactions for flavour production with micro-organisms do not use the complete food raw material as substrate. Isolated and purified single components of food are used as substrates for the micro-organisms. Examples are butterfat from butter, proteins from meat, carbohydrates from plant food materials. Microbial material syntheses may lead to chemically defined pure substances (cf. chapter 3.2.1.1.2). It is also possible to obtain complex mixtures of different compounds. Polysaccharides, natural colours and also complex flavour extracts belong to this category. Figure 3.17 outlines the principle of such processes. 

Polysaccharide materials are the most abundant and diverse molecules present as an integral part of the natural system on this planet. They are renewable, biodegradable and can be cultivated as plant biomass, which is essentially made of polysaccharides. Nature has been using polysaccharides from time immemorial. Polysaccharides serve as structural material (e.g. the cell walls of plant cells), and are used for energy storage in the form of starch in plant cells and as glycogen in the liver cells of animals. 

Marchessault, R.H., Morehead, F.F., Walter, N.M. Liquid crystal systems from fibrillar polysaccharides. Nature. 184, 632-633 (1959a)... 

Fucan is a sulfated polysaccharide, naturally present in algae such as Fucus vesiculosus or Ascophyllum nodosum. Fucan is a general name for a mixtore of three polysaccharides among them, fucoidan (or homofucan) can be theoretically considered as an homopolymer of a-1,2... 

Proteins, polysaccharides, natural rubber, and gums are all natural polymers. The repeat units in proteins are amino acids. Nucleic acids are composed of nucleotides and polysaccharides consist of sugar units. 

Okuda T, Yoshioka Y, Ikekawa T, Chihara G, Nishioka K (1972) Anti-complementary activity of anti-tumor polysaccharides. Nature (London) 238 59-60... 

Maeda YY, Chihara G, Ishimura K (1974) Unique increase of serum proteins and action of antitumor polysaccharides. Nature 252 250-252... 

Jacobs and Ahmadjian (1969), who examined the ultrastructure of ten foliose and fruticose nongelatinous lichens, found a thick (up to 1 /urn) fibrillar material of a polysaccharide nature surrounding the fungal cell wall. A similar extracellular polysaccharide was also found between the cells of the Trebouxia phycobiont. This substance supposedly facilitates the water retention ability of the thallus. 

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