Cyclodextrin production by Bacillus firmus strain 37 immobilized on inorganic matrices and alginate gel

Production of β-cyclodextrin (β-CD) by Bacillus firmus strain 37 cells, immobilized by adsorption on silica–titania (SiO2/TiO2) and silica–manganese dioxide (SiO2/MnO2) matrices, was optimized for temperature, substrate concentration and initial biomass. The immobilization process was most efficient at 60 °C with 10% maltodextrin and 1.0 g of cells, resulting, after a 5-day assay, in a β-CD production of 11.7 ± 0.1 mM for cells immobilized on SiO2/TiO2 and 11.2 ± 0.1 mM in SiO2/MnO2. Entrapment in alginate gel resulted in a maximum β-CD production of 4.1 ± 0.1 mM, which was maintained constantly until the end of a 10-day assay. During this same period, free cells produced 8.3 ± 0.2 mM, and cells immobilized on SiO2/TiO2 and SiO2/MnO2, 16.7 ± 0.4 and 17.3 ± 0.5 mM, respectively. β-CD production by cells immobilized in calcium alginate in four repetitive cycles of 5 days each, showed an increase up to the third cycle, reaching 4.8 ± 0.2 mM, while production by free cells started falling from the second cycle. In this same assay, cells immobilized on SiO2/TiO2 and SiO2/MnO2, showed the best β-CD production results at the end of the first cycle, with a gradual fall occurring due to the desorption of cells thereafter.