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Title: Cation binding by bacterial and algal polysaccharides
Author: Geddie, Joanne Louise
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1992
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The chemical compositions and physical characteristics of a range of bacterial polymers were analysed. The polymer elaborated by Rhizobium meliloti appeared to be a succinoglycan containing acetyl groups whereas the Zoogloea ramigera polymer contained glucose and galactose in the ratio 2:1 and contained acetate and pyruvate. In the presence of cations, the succinoglycan existed in an ordered state, wheras the Zoogloea polymer appeared to exist in a gel like state, rather than a true polymer solution. The bacterial alginates contained various amounts of mannuronic acid (M) and guluronic acid (G) residues. As expected, the Pseudomonas aeruginosa alginate lack contiguous G residues. The alginate from Azotobacter vinelandii 206 was unusual in that it contained a very low amount of G residues. Metal uptake by a range of polymers was carried out by dialysis and samples were analysed using ion chromatography. The alginate samples showed that uptake of the ions was dependent on the ratio of mannuronic acid L: guluronic acid and a binding selectivity of SR > Ca > Mg > K > Na > Li was found. The algal alginates showed greatest uptake and selectivity, although values obtained were low in comparison to published results for alginates in the gel phase. The bacterial alginates showed limited uptake and selectivity. Once the bacterial alginates were deacetylated the uptake and selectivity increased significantly. It is thought that the acetyl groups sterically inhibit the binding of cations. The uptake of cations by polysaccharides isolated from four other bacteria was also exmained. The polysaccharides which contained acetyl groups showed a selectivity of Ca > Mg > monovalent cations, however when the polymers were deacetylated, the selectivity of uptake of monovalent ions was > Mg > Ca. The polymer and ion concentrations were too low to allow gelatin of certain polymers, but even at low concentrations, the acetyl group appeared to play a significant role in ion binding. The reason for the altered selectivity of ion binding following deacetylation is unclear. The Zoogloea polymer had a low capacity to remove cations compared to A3(sl) and XM6 which had the highest uptake capacities. The selectivity coefficients were all close to unity, perhaps suggesting similar ion binding.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available