Alginate Algae

The alginic acid content of some of the commercially important brown algae is shown in Table 4. The commercial processes for the production of algin are proprietary (22,23). 

Sodium alginate is the principal brown algae gum, while the red algae are of two practical types ... 

Improvement of intraparticle mass transfer is the goal of some particle research efforts. One novel approach that has been recently tested is the co-immobilization of algae with bacteria the algae produced oxygen and the bacteria produced the desired product (Chevalier and de la Noue, 1988). Another method used microporous particles entrapped within alginate bead bioparticles to prevent excess biomass growth that could hinder intraparticle mass transfer (Seki et al., 1993). 

These materials are another polysaccharide. The name derives from its original source, brown algae. The current commercial sources are brown seaweeds such as Laminaria digitata, L. hyperborea, Ascophyllium nodosum and Fucus serratus. Different properties are obtained in alginates from different seaweeds. The sources are rocky coasts in the United States, the United Kingdom, France and Norway. 

Ionic cross-linking can be achieved in a number of systems and different microstructures result. For rigid chains it is possible for the ion to coordinate in a specific manner with the chain. Alginates are a good example of this. These are natural polymers derived from a brown macro-algae. The method of extraction and the species of the algae influences the chemistry and hence the rheology of these polymers. There... 

Figure 22.11. Cellulose is a structural and rather chemically inert component of terrestrial plants. Alginic acid is synthesized by marine algae and has medicinal properties. Some polysaccharides contain nitrogen in the form of amino sugars. The primary example of this is chitin, which composes the exoskeletons of Crustacea. An amino sugar contains an amine in place of a hydroxyl group. In other polysaccharides, sugars combine with lipids and proteins. These form glycoUpids and glycoproteins, respectively.

Many marine algae are rich in glycuronans. One of the more technically important materials is alginic acid, composed of D-mannuronic and l-... 

L-Gulose readily forms an anhydride, and in a study on alginic acid, methylated L-guloses were isolated as their anhydrides.88 Other anhydro sugars, such as 3,6-anhydro-L-galactose and its 2-methyl ether, may be found in algae (see, for example, Ref. 412), and, under certain circumstances, 2,3,6-tri-O-methyl-D-galactose may form an anhydride.571... 

Rao and Hall compared the activities of algae, cyanobacteria, and photosynthetic bacteria entrapped in an alginate gel and in a hydrophilic polyurethane. Their opinion was that such systems could maintain effectiveness for years using sunlight as an energy source. 

The polyurethane-entrapped algae showed reasonable activity compared to free suspensions of cells. The activity fell sharply after a few days, however. The authors hypothesized that the decrease could have been the result of residual toxicity of the polyurethanes. They also noted that the previous method of entrapping the cells in alginate gels performed better. Our work focused on tlie differences in diffusion tlirough the entrapping polymer. Baillez et al. also discussed mass transport in the foams as a contributing factor. In summary, direct entrapment resulted in an immediate reduction in viability of the cells. 

Alginic acid is a linear polymer composed of (i-1,4-D-mannuronic and L-gulucuronic acid the proportions of the two units are not constant in the alginates from different algae species (Fig. 11). 

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