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

Levansucrase from Zymomonas mobilis expressed in Escherichia coli was immob ilized onto the surface of magnetite. Optimum conditions for the immobiliza tion 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 condition s. The maximum production yield of levan by the immobilized levansucrase wa s about 42% on a fructose released basis with sucrose as substrate at 100 g /l. Thermal stability of the levansucrase increased by immobilization proce dure. Furthermore, immobilized enzyme showed the less polymerizing activity in levan formation, producing the low-molecular weight (MW) levan. The mol ecular weight of levan can be controlled by using the immobilized levansucr ase in high yield. Immobilized levansucrase retained 61% of the original ac tivity after five repeated uses. (C) 2001 Elsevier Science Ltd. All rights reserved.