Levan production by use of the recombinant levansucrase immobilized on titanium-activated magnetite

Abstract

Levansucrase from Zymomonas mobilis expressed in Escherichia coli was immobilized onto the surface of magnetite. Optimum conditions for the immobilization were, pH 4.0; immobilization reaction time of 30 min and 8 U of enzyme per gram of matrix. Immobilization yield was 75% under optimized conditions. The maximum production yield of levan by the immobilized levansucrase was about 42% on a fructose released basis with sucrose as substrate at 100 g/l. Thermal stability of the levansucrase increased by immobilization procedure. Furthermore, immobilized enzyme showed the less polymerizing activity in levan formation, producing the low-molecular weight (MW) levan. The molecular weight of levan can be controlled by using the immobilized levansucrase in high yield. Immobilized levansucrase retained 61% of the original activity after five repeated uses.