Cyclodextrin production by Bacillus firmus strain 37 cells immobilized on loofa sponge

Loofa sponge, loofa sponge–chitosan, loofa sponge–alginate and synthetic sponge were tested as matrices for the immobilization of Bacillus firmus strain 37 cells for β-cyclodextrin (β-CD) production from dextrin. Similar results were obtained for the matrices studied and loofa sponge was chosen for further studies because of its renewable character and simple method of immobilization. Optimization of the initial biomass, immobilization time and number of loofa discs were carried out. The period of 1 day and the amount of 30 mg of lyophilized cells were sufficient for immobilization on three loofa sponge discs to produce 20.2 mM of β-CD. Operational stability was evaluated in four repetitive cycles of 5 days each and all the matrices studied showed better behavior than free cells. The loofa sponge–alginate matrix showed the best operational stability, mantaining in the second cycle the same β-CD production obtainded in the first cycle and 77% production in the third cycle, whereas the free cells were almost inactive in this cycle. The innovative use of loofa sponge, an environmentally friendly matrix, for β-CD production gave good performance at an affordable cost, thus making the process potentially suitable for industrial scale-up.