Monday, August 13, 2012
Columbia Hall, Terrace Level (Washington Hilton)
Cyclodextrin have been used as catalyst in several reactions due to morphological properties like truncated conical shape and in chemical reactor to synthesize nanoparticles systems. The cyclodextrin production involves the starch treatment with the enzyme cyclodextrin glycosyltransferase (CGTase) by means of cycling, coupling and disproportioning reactions. In order to use the CGTase from Bacillus lehensis, a bacterium isolated from a cassava flour mill in Brazil, the present work show studies of the CGTase immobilization on nanoparticles of magnetite. The nanoparticle was obtained by hydrothermal synthesis process from cyclodextrin and ferric chloride. The CGTase was immobilized by covalent bound on magnetic surface; the magnetite used was obtained from hydrothermal synthesis of cyclodextrin-ferric chloride system. The immobilization process was prepared by magnetite silanization reaction using 3-aminopropyltriethoxysilane and activation with glutaraldehyde. The effects of buffer, aminopropyltriethoxysilane and glutaraldehyde solutions, enzymatic concentrations and reaction temperatures on CGTase immobilization in magnetite were studied. The immobilized CGTase was recovered by magnetic separation and showed a constant enzymatic activity during their reuse. The characterization of immobilized CGTase in magnetite was realized. Optimum conditions of pH and temperature, temperature and pH stability, influence of substances in enzyme action and enzymatic kinetics were analyzed. Enzymatic characterization exhibited optimum pH and temperature of 8 and 70°C, respectively. The enzyme was stable at 70°C for 80 min. and at pH from 3.0 to 10 for 24 h. The stability of the CGTase from Bacillus lehensis increased substantially after immobilization on magnetite surface nanoparticles.