Abstract
Sodium alginate and chitosan were cross-linked to form composite gel spheres, which were entrapped to immobilize the free neutral protease. The matrix of the immobilized neutral protease was detected and characterized by using Fourier transform infrared spectroscopy and energy-dispersive X-ray. The optimum immobilization conditions were determined by orthogonal test, in which the concentration of sodium alginate was 3.5%, CaCl2 2.5%, chitosan 2.5%, and immobilizing time 1.5h. Meanwhile, the activities of immobilized neutral protease and free enzyme were compared. The results showed that the pH value of immobilized enzyme was 5-8, the relative activity was above 90%, the free enzyme was above 80%, the relative activity of immobilized enzyme was above 80% in 30-80°C, and the free enzyme was above 64% in 40-80°C. The immobilized enzyme is better than the free enzyme in the constant of pH and temperature. The relative activity of immobilized enzyme was 50% after six hydrolysis cycles, and 80% after 11days of storage.
Highlights
The dilution of 1 mg/L neutral protease was 5000 times, and the mixture of diluted protease solution and sodium alginate was oscillated at a volume of 1:3 for 40 min at room temperature
The results showed in figure 3(c), the immobilized enzyme was reused for 6 times, the relative activity of the immobilized enzyme remained above 50% at the 6th times, which fully indicated the high reuse efficiency of the immobilized enzyme
The effects of immobilized conditions on the enzymological properties of immobilized neutral protease were investigated by using enzyme activity as an index
Summary
Enzymes are used to speed up biochemical and chemical reactions. It has been widely used in various fields because of its high catalytic efficiency and substrate specificity under appropriate reaction conditions (suitable pH, temperature, etc.) [1]. Immobilized enzymes can overcome these problems, and has some advantages including repeated application in the same catalysis reaction, increased reaction control of the catalytic process, rapid termination of reactions with ease by removal of enzyme from the reaction mixture. The immobilized enzyme can remain active in more widely range of pH and temperature condition due to the increased conformation stability[2]. Enzyme immobilization restricts the enzyme to the carrier through simple adsorption, covalent binding, embedding or different combinations of methods, which does not significantly affect the activity of the enzyme, and improves the stability[3,4]
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