การหาภาวะที่เหมาะสมในการตรึงรูปเดกซ์แทรนเนสบนผิวทรายในเครื่องปฏิกรณ์แบบฟลูอิดไดซ์เบด / นฤมล วงศาสุข = Optimization process of dextranase immobilisation onto sand in fluidized bed reactor / Naruemon Vongsasook
The parameter of immobilization of dextranase such as pH, enzyme concentration, glutaraldehyde concentration and contact time on immobilization of dextranase in shake flask and fluidized bed reactor were studies. The properties of the immobilized dextranase such as optimum pH, temperature, thermal stability, pH stability, Michaelis constant (K[subscript m]) and reusability were also studied. The optimum conditions for the preparation of immobilized dextranase in fluidized bed reactor were with 2.5% by volume of glutaraldehyde and the maximal enzyme loading on sand was 0.4 to 1.5 mg/g.sand (dry weight). Immobilization was performed at room temperature with agitation speed 200 rpm for shake flask and aeration rate at 2.0 vvm for immobilization in fluidized bed reactor. Times and pH for glutaraldehyde cross-linking were 120 mins in shake flask and 60 mins in reactor at pH 7.0 and immobilizing steps were 45 mins for shake flask and 30 mins in reactor at pH 4.0. Compared with free dextranase, the immobilized dextranase showed similar optimal temperature (55 degree celcius), shift in pH optimum, the immobilized dextranase was found to be at pH 4.5. The K[subscript m] value of the immobilized and free dextranase was found to be at 0.002 mM and 0.0009 mM respectively. Following repeated use, the immobilized dextranase retained 25% of initial activity after the sixth hydrolysis cycle.