Biopolymers

The main work in this field at present is on the polysaccharide alginate, which has several commercial applications. Due to its gelling, water-binding, and viscosity-enhancing properties alginate is widely used in foods, and has other industrial applications as different as in textile printing and welding rods. It is also used for medical purposes, such as encapsulation of cells. One example of the latter is the use of alginate for the encapsulation of insulin-producing cells for better treatment of patients suffering from diabetes. We have isolated alginate over-producing mutants of Pseudomonas fluorescens and are studying genes involved in the production of the polymer. We are also combining this knowledge with knowledge of different Pm-promoters (see Gene Expression) and of the alginate modifying enzymes to engineer production strains for different types of alginates.

Key Papers

Gimmestad M, Sletta H, Ertesvag H, Bakkevig K, Jain S, Suh SJ, Skjak-Braek G, Ellingsen TE, Ohman DE, Valla S. (2003). The Pseudomonas fluorescens AlgG protein, but not its mannuronan C-5-Epimerase activity, is needed for alginate polymer formation. J Bacteriol. Jun 15;185(12):3515-3523.

Alginate modifying enzymes

Alginate is a polymer produced by algae and some microorganisms. Our main focus has been on the mannuronan C-5-epimerases, which determine the structure of alginate. Azotobacter vinelandii encodes a family of secreted epimerases in addition to the periplasmic AlgG. We are currently studying the structure-function relationship of the epimerases. The production of alginate is important for the A. vinelandii life cycle, and we are studying the expression of different epimerases in relation to this. We have also been working on the characterization of several bacterial lyases.

Key Papers

Valla S, Li J, Ertesvag H, Barbeyron T, Lindahl U. Hexuronyl C5-epimerases in alginate and glycosaminoglycan biosynthesis. Biochimie. 2001 Aug;83(8):819-30. Review. PMID: 11530215

Ertesvag H, Erlien F, Skjak-Braek G, Rehm BH, Valla S. (1998) Biochemical properties and substrate specificities of a recombinantly produced Azotobacter vinelandii alginate lyase. J Bacteriol. 1998 Aug;180(15):3779-84. PMID: 9683471; UI: 98348436

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Bioprospecting of marine microorganisms
Biosyntesis of L-Lysin from Methanol
Engineered antibiotic synthesis
Gene Expression
Osmoregulation
Metabolic Engineering