Azotobacter alginate

Alginate is extracted from brown algae (Phaeophyceae), including Laminaria digitata, Laminaria hyperborea. Laminaria japonica, Macrocystis pyrifera, and Ascophyllum nodosum [27] by treatment with aqueous alkali (NaOH) solutions [28], The filtered extract is treated with sodium or calcium chloride to precipitate alginate. Azotobacter and Pseudomonas may produce alginate by a biosynthesis pathway. 

A strain of Azotobacter vinelandii was cultured in a 15 m3 stirred fermenter for the production of alginate. Under current conditions the mass transfer coefficient, kLa, is 0.18 s. Oxygen solubility in the fermentation broth is approximately 8 X 10 3 kgm-3.9 The specific oxygen uptake rate is 12.5 mmol g 1 h. What is the maximum cell density in the broth If copper sulphate is accidentally added to the fermentation broth, which may reduce the oxygen uptake rate to 3 mmol g 1 h 1 and inhibit the microbial cell growth, what would be the maximum cell density in this condition ... 

Several other processes were investigated and developed as well, e.g., a) Am-bruticin S production in airlift and stirred tank reactor b) high-cell density cultivation of E. coli and production of rDNA products c) production of thermostable xylanase by Thermomyces lanuginosus d) cultivation of Tetrahymena thermophila in 1.5 bioreactors, e) alginate production by Azotobacter vine-landii. 

Formation of L-guluronic acid, a component of the alginic acid-like polysaccharide produced by P. aeruginosa and Azotobacter vinelandii, requires special comment. In this case, a polymer built from /3-(l- 4)-linked D-mannosyluronic acid residues serves as an intermediate in the biosynthesis.204,205 Part of the D-mannosyluronic acid residues in the polymer is subjected to an epimerization at C-5 catalyzed by an exocellular enzyme of the micro-organism,205-207 producing a polysaccharide composed of structural blocks that contain only D-mannosyluronic acid or only l-gulosyluronic acid residues, as well %s some having both. The mechanism of the epimerization remains unclear. 

Alginate Pseudomonas aeruginosa Azotobacter vinelandii Range of viscosity types gels with Ca2 + textile printing, food applications... 

With xanthan gum, continuous fermentation243-245 resulted in lower estimates of cost for its production. Also, with the production of bacterial alginate by Azotobacter vinelandii, serious loss of substrate by respiration could be minimized by proper selection of the conditions in the continuous fermentor.62 With some micro-organisms, the desired metabolites are not produced, owing to selection of less-productive strains. Apparently, this selection occurred with Xanthomonas campestris246 when Rogovin and coworkers243-245 found that production of xanthan decreased after —8-10 fermentor turnovers. 

Alginates are also produced extracellularly by some bacteria, such as Pseudomonas aeruginosa and Azotobacter vinelandii [100], where they are believed to play a role in biofilm formation, pathogenesis, and soil aggregation. Their gels, however, are inferior to seaweed alginates, because of the presence of 0-acetylation, which inhibits gel formation. 

Alginates were first described by Standford in 1881 [1]. They were originally discovered thanks to industrial developments related to iodine production. Alginates are quite widespread in Nature. They can be found as major cell-wall components (up to 45% of the dry matter) in marine brown algae (Phaeophyceae). They also occur in acetylated form as exopolysaccharides produced by bacteria belonging to Pseudomonas and Azotobacter genders. 

Alginate is a gelling polysaccharide found in great abundance as part of the cell wall and intracellular material in the brown seaweeds (Phaeophyceae). Most of the alginate used commercially is obtained from Macrocystis, Laminaria, and Ascophyllum [137]. Recently, Azotobacter vinelandii, a nitrogen-fixing bacterium... 

The primary methods used in cell immobilization are surface adhesion, covalent attachment and entrapment. Surface adhesion involves adsorption of cells to microcarriers such as calcium alginate beads, collagen-coated plastic beads, diatomite silica, and dextrans [68]. Immobilization can be achieved simply by suspending the cells and microcarrier together under slow agitation. Examples of such systems include immobilized bacteria for waste water treatment and adsorbed Azotobacter vinelandii on Cellex E for nitrogen fixation... 

The biosynthesis of alginic acid [69, 243, 244] has been investigated in both seaweeds and bacteria. Azotobacter vinelandii produces exopolysaccharide in a high carbon-low nitrogen environment and hexoses, disaccharides and D-mannitol can all provide a carbon source. This bacterium contains enzymes that convert hexose phosphates into GDPMan (reactions A to D and J) which then undergoes oxidation and polymerisation... 

Alginate Pseudomonas spices and Azotobacter vinelandii For the production of micro- or nanostructures suitable for medical applications... 

The kind of polysaccharides that are isolated from different bacteria are as follows Alginate, a linear copolymer with (l-4)-linked p-D-mannuronate and its a-L-guluronate residues that is produced by two bacterial genera Pseudomonas species and Azotobacter vinelandii [4]. Bacterial alginates are useful for the production of micro- or nanostructures suitable for medical applications. Cellulose, a p (1—>4) linked D-glucose unit obtained from Acetobacter xylinum. Cellulose of plant origin is usually impure as it contains... 

Materials. Alginic acid (sample S-35) produced by Azotobacter vinelandii (1) was a kind gift of Dr.K.C.Symes, Tate and Lyle... 

Clementi, F., Mancini, M., Moresi, M. Rheology of alginate from Azotobacter vinelandii in aqueous dispersions. J. Food Eng. 36, 51-62 (1998)... 

Figure 2. Apparent viscosity vs. rate of shear plots for Azotobacter alginates and certain...

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