Continuous production of inulo-oligosaccharides from chicory juice by immobilized endoinulinase

Abstract

Several carrier materials were examined for endoinulinase immobilization. A polystyrene carrier material (UF93®) gave the best immobilization capacity (217 units/g carrier) and operational stability. Carbohydrate compositions in the reaction product were quite similar irrespective of the support materials even though each carrier material has different pore structure associated with diffusional restriction. After immobilization the optimal pH for enzyme activity was shifted from 5.0 to 4.5, whereas optimal temperature (55 °C) was unaltered. Continuous production of inulo-oligosaccharides from chicory juice was carried out using the polystyrene-bound endoinulinase. The recommended operating conditions of the enzyme reactor for maximizing productivity were as follows: feed concentration, 100 g/l chicory juice; flow rate, as superficial space velocity 2.0 h-1; temperature, 55 °C. The enzyme reactor was run for 28 days at 55 °C achieving an oligosaccharide yield of 82% without any significant loss of initial enzyme activity, where the volumetric productivity was 200 g/l · h. Furthermore, there was no marked difference in operational stability between the two reactors fed with pure inulin solution and with chicory juice as a substrate even though chicory juice contains a lot of impurities.