Immobilization of a thermostable alpha-amylase

Abstract

Cellulose fibers from bagasse were oxidized by periodic acid at positions 2 and 3 of the anhydroglucose unit to obtain dialdehyde cellulose. The aldehyde groups of the dialdehyde cellulose were able to react with amino groups of a thermostable alpha-amylase to form covalent bonds and resulted in a dialdehyde cellulose immobilized enzyme. The optimum pH of this immobilized enzyme was pH 7-9 while that of the free enzyme was pH 7.0. The optimum temperature for free and immobilized enzymes was 90 °C and 95 °C, respectively. The activity yield of the immobilized enzyme was 44% . Thermostable alpha- amylase is normally used as starch liquefying enzyme in the production of dextrose. The stability of immobilized enzyme was tested by studying its ability to liquefy 5% gelatinized tapioca starch over 10 reused cycles. The viscosity of 5% gelatinized tapioca starch solution was 2330 cP, while viscosity of the liquefied starch solution produced by the reused immobilized enzyme after more than 10 reused cycles was only 50 cP. Thus, it was very effective in reducing starch viscosity and the immobilized enzyme was very stable.