Immobilization of α-amylase on nanoporous zeolite: improved stability and reusability

α-Amylase is one of the important biocatalyststhat hydrolysis of internal α-1,4-glucosidic linkage in starch and related oligosaccharides that widely used in the foodand detergent industry. Enzymes are sensitive against harsh condition such as acidic pH and heating and could not be recovered also. These restrictions could beimproved by enzyme immobilization that converts water soluble enzymatic proteins into the solid form. Nanoporous zeolite with special features such as mechanical and thermal stability, non-toxicity, high stability against microbial attack and insolubility in organic solvents could be used as a matrix for enzyme immobilization. This study immobilized α-amylase from Aspergillus oryzaeon the nanoporous zeolite bed with aldehyde group adding method. Free and immobilized α-amylase enzyme activity was measured by the dinitrosalicylic acid method at 450 nm with starch as substrate. Nanoporous zeolite was activated by Glutaraldehyde and the yield of covalent immobilization calculated as 59.34 . Optimum temperature range for free and immobilized enzyme activity measured between 45-55 C and optimum pH assessed 8-8.5. Thermostability of immobilized enzyme was significantly increased rather than free enzyme and stability against high pH also was more for fixed enzyme. Storage stability in 4C and thermal stability in 65 C for immobilized enzyme estimated more than free enzyme (near to 5 folds), which is important for industrial application of enzymes. Our immobilizedenzymes are reusable and could be recovered 10 times without significant decrease in starch hydrolyzing ability. Improved functional stability of immobilized enzyme makes it as an economic enzyme in industry.

Keywords:

α-Amylase , Functional stability , Thermostability , Storage stability