3.4. Enzymatic Activity Assay of the Alginate Lyase

To determine the activity of recombinant enzyme, 100 μL of appropriately diluted AlyS02 was mixed with 900 μL of substrate solution (1% (w/v) sodium alginate, 20 mM Tris-HCl buffer, pH 7.6), and incubated for 10 min at 30 °C. The solution was heated in boiling water for 10 min to terminate the reaction. Then, 1 mL of 3, 5-dinitrosalicylate (DNS) solution was added to the solution, and the mixture was reacted in a boiling water bath for 10 min. Finally, the absorbance was measured at 540 nm. One unit of alginate lyase activity was defined as the amount of enzyme required to release 1 μmol of reducing saccharides (glucose equivalent) per min.