7-74: Production of monomeric sugars from alginate using two types of alginate lyases

Macroalgae are now considered to be a biomass for fuels and chemicals production. To utilize brown macroalgae, the degradation of its main carbohydrate, alginate, into monomeric sugars is a critical prerequisite step. A putative alginate lyase from Saccharophagus degradans 2-40, alg7D, belonging to the family of polysaccharide lyase-7, was overexpressed in Escherichia coli, and Alg7D was found to endolytically depolymerize alginate by β-elimination into oligoalginates with degrees of polymerization of 2 to 5. The Alg17C gene from S. degradans, which is classified into the PL-17 family, was also overexpressed in E. coli. The recombinant Alg17C was found to preferentially act on oligoalginates with degrees of polymerization higher than 2 to produce the alginate monomer, 4-deoxy-L-erythro-5-hexoseulose uronic acid. The combination of Alg7D and Alg17C could be used as the key enzymes to produce alginate monomers in the process of utilizing alginate for biofuels and chemicals production.