Production of levan using recombinant levansucrase immobilized on hydroxyapatite

Levansucrase of Zymomonas mobilis was immobilized onto the surface of hydro xyapatite by ionic binding. Optimum conditions for the immobilization were: pH 6.0, 4 h of immobilization reaction time, and 20 U of enzyme/g of matri x. The enzymatic and biochemical properties of the immobilized enzyme were similar to those of the native enzyme, especially towards the effect of sal ts and detergents. The immobilized enzyme showed sucrose hydrolysis activit y higher as that of the native enzyme, but levan formation activity was 70% of the native enzyme. HPLC analysis of levan produced by immobilized enzym e showed the presence of two different types of levan: high-molecular-weigh t levan and low-molecular-weight levan. The proportion of low-molecular-wei ght levan to total levan produced by the immobilized enzyme was much higher than that with the native enzyme, indicating that immobilized levansucrase could be applied to produce low-molecular-weight levan. Immobilized levans ucrase retained 65% of the original activity after 6 times of repeated uses and 67% of the initial activity after 40 d when stored at 4 degrees C.