Seaweeds, also known as macroalgae, constitute a rich source of valuable biomolecules which have a potential industrial application in food and pharma products. The use of enzymes can optimize the extraction and separation of these molecules from the seaweed biomass, but most commercial enzymes are incapable of breaking the complex polysaccharides found in seaweed cell walls. Therefore, new enzymes are needed for degradation of seaweed biomass.
Bacteria that colonize the surfaces of seaweed secrete enzymes that allow them to degrade and utilize seaweed polysaccharides as energy. In addition, sea urchins are known algae-eaters and may therefore be inhabited by endosymbiotic bacteria that help in degradation of algal cell wall constituents.
This thesis work investigated bacteria associated with seaweed, seagrass and sea urchins for their enzymatic activities against algal cell wall polysaccharides.
A novel agar-degrading bacterium, named Paraglaciecola hydrolytica, was isolated from seagrass and investigated in more detail. Growth studies and whole-genome analyses showed that P. hydrolytica was
capable of degrading a wide range of algal polysaccharides including agar and carrageenan. The agarolytic system of P. hydrolytica featured several inducible agarase genes and five of these agarases were functionally characterized. Likewise, putative formylglycine sulfatase genes were induced when P. hydrolytica was grown in presence of agar and indicated an involvement of these sulfatases in agar degradation. In addition, three carrageenases were characterised; one as a GH16 κ-carrageenase whereas the other two belong to a new GH16 subfamily of enzymes that degrade furcellaran (κ/β-carrageenan).
From metagenome sequence data three putative GH107 fucanases were identified and characterized. These enzymes degraded fucoidan extracted from brown algae of the order Fucales, but displayed individual substrate preference and degradation pattern. This work adds substantial information to a protein family which is largely undiscovered to date.
Several of the enzyme activities discovered in this thesis have not been previously reported and
may aid researchers as well as industrial sectors.
Assessment Committee: