Preparation and properties of mycelium-bound glucose isomerase co-immobilized with glucoamylase, and continuous production of high fructose-syrup directly from liquefied starch.

Abstract

Glucoamylase (GA) was linked to mycelia-bound glucose isomerase (GI) with glutaraldehyde in the presence of tannic acid and the GA-linked mycelia were entrapped in K-carrageenan gel-cubes. The resulting co-immobilizate was obtained in the yields of 28 and 37% for the GA and GI activities, and its GA and GI activities were 0.12 and 0.059 U/mg solid, respectively. The co-immobilization insignificantly altered the optimum temperature and heat stability of both enzymes but slightly shifted the profile of the pH-GA activity toward alkaline side and increasedthe KM (25 mM) of the GA for maltose and maltotriose. The column reactor packed with the co-immobilizate continuously produced during four weeks the isosyrup having a higher than 44.1% fructose, a lower than 51.8% glucose, and a lower than 4.1% oligosaccharides, from 30% liquefied starch with an average degree of polymerization of 4.0 under the optimum conditions : pH 6.8, 55°C, and the space velocity of 0.1 hr-1. The half-life values of the GA and GI activities were 40 and 50 working days, respectively.