Sucrose hydrolysis by thermostable immobilized inulinases from Aspergillus ficuum

摘要

The possibility of using thermostable inulinases from Aspergillusficuam in place of invertase for sucrose hydrolysis was explored. T commercial inulinases preparation was immobilized onto porous glass beads by covalent coupling using activation by a silane reagent a glutaraldehyde before adding the enzyme. The immobilization steps were optimized resulting in a support with 5,440 IU/g of supp (sucrose hydrolysis) that is 77% of the activity of the free enzyme. Enzymatic properties of the immobilized inulinases were similar to tho of the free enzymes with optimum pH near pH 5.0. However, temperature where the activity was maximal was shifted of 100C due to bet! thermal stability after immobilization with similar activation energies. The curve of the effect of sucrose concentration on activity w bi-phasic. The first part, for sucrose concentrations lower than 0.3 M, followed Michaelis-Menten kinetics with apparent KM and Vm on slightly affected by immobilization. Substrate inhibition was observed at values from 0.3 to 2 M sucrose. Complete sucrose hydrolysis w obtained for batch reactors with 0.3 and 1 M sucrose solutions. In continuous packed-bed reactor 100% (for 0.3 M sucrose), 90% (1 1 sucrose) or 80% sucrose conversion were observed at space velocities of 0.06—0.25 h The operational half-life of the immobilize inulinases at 500C with 2 M sucrose was 350 days.