เดกซ์แทรนเนสตรึงรูปบนทรายสำหรับการกำจัดเดกซ์แทรนในน้ำอ้อยอย่างต่อเนื่อง / พรทิพย์ จารุพันธ์ = Dextranase immobilized on sand for continuous removal of dextran in sugar cane juice / Pronthip Jarupan
The optimum condition for preparation of immobilized dextranase by covalently binding method were : 50-60 mesh river-bed sand as carrier, 5% by volume of APTS solution as carrier activator, 1% by volume of glutaraldehyde solution as intermolecular cross-linker, and 5% by volume of dextranase solution (788800 unit/ml) at 4 degree celsius, pH 4.5 for 90 min with shaking. The optimum pH for dextran hydrolysis of the immobilized dextranase and the free dextranase were 7.0 and 5.0, respectively. Both free and immobilized dextranase had optimum temperature for dextran hydrolysis at 55 degree celsius. The Michaelis constant, K (subscript m) of the immobilized dextranase at 55 degree celsius and pH 7.0 was 3.67x10(superscript -4)mM which was 1.93 times lower than of free dextranase. The specific activity of immobilizeddextranase at pH 5.5, 40 degree celsius was 6574.07 unit/mg protine which was 3.09 times lower than that of free dextranase. Moreover, in the presence of 20% sucrose, the thermal stability of the immobilized and free dextranase was high. The optimum condition for storage stability of immobilized dextranase was pH 3.5 at 8-10 degree celsius and the half life under this condition was > 81 days and the retained activity was 82.6%. In the enzyme reaction studies with inorganic salt and chelating agent (6x10(superscript-3)M), it was found that the immobilized form was less inactivated in the presence of AgNO(subscript 3)Ca(OH)(subscript 2) and Zn(AcO)(subscript 2). Furthermore, K(subscript 3) Fe(CN)(subscript 6)inactivated free dextranase but activated the immobilized dextranase. The hydrolysis of dextran in mixed juice at pH 5.0 using the immobilized dextranase in fluidized bed reactor 1.4x60 cm was studied. The optimum space velocity (SV) was 1.62 (min)(superscript-1).The degree of hydrolysis of dextran at 55 degree celsius was higher than at room temperature. The degree of hydrolysis was up to nearly complete when only 2 cycles of cane juice was passed. Moreover, it was found that the decay temperature showed the same decay profile.