RESUMO
Ulocladium atrum inulinase was immobilized on different composite membranes composed of chitosan/nonwoven fabrics. Km values of free and immobilized U. atrum inulinase on different composite membranes were calculated. The enzyme had optimum pH at 5.6 for free and immobilized U. atrum inulinase on polyester nonwoven fabric coated with 3% chitosan solution (PPNWF3), but optimum pH was 5 for immobilized U. atrum inulinase on polyester and polypropylene nonwoven fabrics coated with 1% chitosan solution. The enzyme had optimum temperature at 40°C for immobilized enzyme on each of polyester and polypropylene composite membranes coated with 1% chitosan, while it was 50°C for free and immobilized enzyme on polypropylene nonwoven fabric coated with 3% chitosan solution. Free U. atrum inulinase was stable at 40°C but thermal stability of the immobilized enzyme was detected up to 60°C. Reusability of immobilized enzyme was from 38 to 42 cycles of reuse; after this, the immobilized enzyme lost its activity completely. In conclusion, immobilized U. atrum inulinase was considerably more stable than the free enzyme, and could be stored for extended periods.