LSU Historical Dissertations and Theses

1994

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

School of Nutrition and Food Sciences

Donal F. Day

Abstract

Alginate has many industrial uses because of its unique colloidal behavior, and its ability to thicken, stabilize, emulsify, suspend, form films, and produce gels. Currently, all commercial alginate comes from brown algae, where it exists naturally as a structural material. Many different types of brown algae produce alginate but it can only be obtained in sufficient quantity and quality from a limited number of species. On the basis of location, at least half of the world's resources of this polymer are potentially at risk due either to political instability or industrial pollution. Bacteria provide a potentially unlimited alternate source for alginate. Pseudomonas syringae pv phaseolicola ATCC 19304, produced an acetylated alginate-like polysaccharide with a weight average molecular weight (M$\sb{\rm w}$) of $1.2 \times 10\sp5$. This bacterial polymer was composed of 82% mannuronic acid and 18% guluronic acid. Compositional analysis of the reduced alginate polymer showed that L-gulose was more sensitive to acid degradation than D-mannose. The percentage of gulose recovered at various hydrolysis times was extrapolated to zero hydrolysis time to account for the loss of gulose. Acetylation affected the solution and gelling properties of the polymer. Acetylated bacterial alginate showed increased viscosity, and water holding capacity, and altered cation precipitability over unacetylated alginates. By controlling the degree of acetylation on the bacterial alginate, the solution and gelling properties of the polymer can be manipulated and the polymer targeted to specific applications.

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