Relationship between potato starch isolation methods and kinetic parameters of hydrolysis by free and immobilised α-amylase on alginate (from Laminaria digitata algae)

The kinetic study of the hydrolysis of starch, isolated by two methods (bisulphite and alkaline) from potatoes cultivated in the south of Algeria, was carried out by α-amylase (from Aspergillus oryzae). The enzyme used is free and immobilised by covalent bonds on alginate in the presence of the 1-ethyl-3-[3-(dimethylamino)-propyl]carbodiimide hydrochloride (EDCI). The kinetics of hydrolysis of the extracted starches obeys the Michaelis–Menten model. The values of km in g L−1 and Vmax in g L−1 min−1 for the starches isolated by the alkaline method are (40.7, 3.8) for free amylase and (70.8, 3.4) for the immobilised enzyme. For the starches extracted by the bisulphite method, the latter kinetic parameters values are (34.2, 2.8) for free amylase and (55.7, 1.7) for the immobilised enzyme. The results show that the kinetic parameters of the hydrolysis are dependent on the conditions of extraction and they are larger for the alkaline method for both the free and immobilised enzyme.