Bacillussp. DSM 2523 entrapped within chitosan beads used as the whole cell biocatalyst for the production of cyclodextrin glucanotransferase in a fluidized bed bioreactor

Abstract

The production of cyclodextrin glucanotransferase (CGTase) from starch with the use of Bacillus sp. DSM 2523 cells entrapped within chitosan beads was studied in a constructed fluidized bed reactor. The experiments were monitored in terms of b-cyclodextrin (b-CD) formation and starch utilization. The central composite design concept was applied to statistically describe the effects of biocatalyst loading and initial starch concentration. The b-CD production and starch utilization were expressed according to quadratic and two-factor interaction models, respectively. The hydrodynamics of the reactor were characterized using chitosan beads of various sizes. The dependence of the drag coefficient on the terminal settling velocity (U t,s ) and terminal Reynolds number was determined. The minimum fluidization velocity was estimated from the Ergun equation based on the relationship between the Reynolds number at minimum fluidization and the Archimedes number. The exponential expression of Richardson-Zaki was applicable in describing the influence of the ratio of the superficial liquid velocity to U t,s on the bed voidage.