Enzymatic modification of alginates with the mannuronan C-5epimerase AlgE4 enhances their solubility at low pH

The recent availability of mannuronan C-5 epimerase from Azotobacter vinelandii opens up for modifying the sequential structure of alginates in a controlled way. To investigate the effect of an increased amount of alternating sequences on the acid solubility of alginate, different alginates from Durvillea antarctica, Lessonia nigrescens, Laminaria hyperborea and a bacterial mannuronan were epimerized using AlgE4. This enzyme is produced recombinantly in Escherichia coli and converts the M blocks into MGM sequences leaving the G-blocks intact. The solubility of the modified alginates was investigated as a function of pH and time.