Immobilized enzyme

About: Immobilized enzyme is a research topic. Over the lifetime, 15282 publications have been published within this topic receiving 401860 citations.

Immobilization and characterization of β‐galactosidase in thermally reversible hydrogel beads

Abstract: Beta-Galactosidase has been immobilized within thermally reversible hydrogel beads and has been studied in batch and packed bed reactor systems. The enzyme was entrapped in a copolymer hydrogel of N-isopropylacrylamide (NIPAAm) and acrylamide (AAm) as beads were formed in an inverse suspension polymerization. A reversible deswelling and reswelling of the hydrogel matrix was induced by first warming and then cooling through 37-40 degrees C, which is the lower critical solution temperature, LCST, of the backbone copolymer. The optimum temperature for maximum activity of the immobilized enzyme-gel bead system was found to be 30-35 degrees C in a batch mode and 40 degrees C in a packed bed reactor, which were both below the 50 degrees C optimum for the free enzyme. These differences are understandable, since the mass transfer rates of substrate and product within the pores of the gel matrix are controlled mainly by the temperature, so therefore it is the temperature which governs the overall activity of the immobilized enzyme system. It was also found that when the operational temperature in the packed bed reactor was cycled between temperatures below (35 degrees C) and above (45 degrees C) the copolymer gel LCST, the activity of the immobilized enzyme almost fully recovered after each cycle. In fact, the enzyme-gel system exhibited a complete "shut-off" in activity at 50 degrees C which was the temperature where the free enzyme showed its maximum activity. The thermal cycling operation of LCST enzyme-gel beads can be used to enhance overall activity and productivity of a packed bed reactor, when compared to isothermal operation of this reactor. This is due to the thermally induced "pumping" which enhances mass transfer rates of substrate in and product out of the gel beads.

Methylphenazonium-modified enzyme sensor based on polymer thick films for subnanomolar detection of phenols

Abstract: A methylphenazonium-zeolite-modified enzyme sensor based on a planar, screen-printed, two-electrode arrangement is described for the subnanomolar detection of phenols. Using tyrosinase (EC 1.14.18.1), a novel polyurethane hydrogel was applied for immobilization and stabilization of the enzyme, which forms a self-adhering layer on the active surface of the strip sensor. Performance and characteristics of the sensor were evaluated with regard to response time, detection limit, selectivity, and dependences on temperature and pH as well as operating and storage stabilities. The sensor shows marked sensitivity to eight phenolic compounds usually present in industrial waste waters. The detection limit for phenol was obtained with 0.25 nM

Immobilization of enzymes on clays and soils

Abstract: Various enzymes such as glucose oxidase, β- d -glucosidase, acid phosphatase. tyrosinase and laccases were immobilized on clays and soils activated with 3-aminopropyltriethoxysilane and glutaraldehyde. After immobilization the enzymes retained a large amount of their original activities. The retention of laccase activity increased with the increase of clay content in soils, whereas the activity of β- d -glucosidase, tyrosinase and acid phosphatase decreased. The immobilized enzymes showed varying degrees of resistance to proteolysis and storage at high temperatures. After addition to soil suspensions, soluble laccase and glucose oxidase were rapidly inactivated (100 and 85% loss of activity in 15 days for laccase and glucose oxidase, respectively) whereas after immobilization, these enzymes were extraordinarily stable (12 and 25% loss of activity in 15 days for laccase and glucose oxidase, respectively). The possibility of incorporating the stabilized enzymes into soil for the improvement of numerous desired biochemical processes is discussed.