Cloning and molecular characterisation of four alginate lyase genes from Vibrio midae SY9 : an enteric bacterium from the abalone Haliotis midae

Doctoral Thesis


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University of Cape Town

Alginate is a linear, un-branched polysaccharide of (1-4)-linked -D-mannuronate (M) and its C-5 epimer, -L-guluronate acid (G). These uronic acids are arranged in three different block types in the alginate polymer; poly-M, poly-G or poly-MG. Alginate lyases are enzymes that utilize a -elimination reaction to depolymerise the alginate polymer resulting in cleavage of the (1-4)-O-glycosidic linkage between monomers and the formation of an unsaturated uronic acid at the new non-reducing terminus. Alginate lyases have been isolated from a wide range of sources including marine invertebrates and marine bacteria, which often produce more than one alginate lyase enzyme. Haliotis midae is the commercially important abalone species found along the South African coast. Over-fishing and poaching of this species has led to a depletion of the naturally occurring populations and closure of the recreational and commercial fisheries. Abalone farming was initiated and has rapidly increased in response to the increasing demand for this delicacy. However, there are many problems associated with abalone aquaculture, the most significant being disease and the slow growth rates of the animals. The use of probiotics in abalone aquaculture is a potential solution to both of these problems.

Includes abstract.

Includes bibliographical references (leaves 241-268).