Alginate is a linear 1-4-linked copolymer of β-d-mannuronic acid and its C-5-epimer α-l-guluronic acid. The polymer is produced by some algae and bacteria, and is used for numerous purposes in industry. Alginate is initially synthesized as mannuronan, which is then modified at the polymer level by mannuronan C-5-epimerases, alginate lyases, and O-acetylases. This generates a variety of heteropolymers where properties such as viscosity, chain stiffness, gel formation, water-binding potential, and immunogenicity are dependent on the action of the modifying enzymes. Both alginate lyases and C-5-epimerases can be used in vitro to tailor alginates for specific purposes. The lyases may also be used as tools to better define the sugar monomer sequences of an alginate sample.