Continuous production of β-cyclodextrin by cyclodextrin glycosyltransferase immobilized in mixed gel beads: Comparative study in continuous stirred tank reactor and packed bed reactor

Abstract

Cyclodextrin glycosyltransferase (CGTase) from Bacillus sp. C26 was highly stable when it was immobilized in mixed alginate–gelatin gel beads. Enzymatic synthesis of β-cyclodextrin (β-CD) from starch by immobilized CGTase was performed in a continuous stirred-tank reactor (CSTR) and a packed-bed reactor (PBR). A comparative study on reaction kinetics found that the apparent maximum production rate (Vmax,app) for reaction in CSTR (0.5742gL−1h−1) was higher than that in PBR (0.33gL−1h−1) likely due to the higher mass transfer rate in CSTR. The lower apparent Michaelis–Menten constant (Km,app) in PBR (31.88gL−1) compared to that in CSTR (58.3gL−1) indicate that the enzyme in PBR required lower amount of substrate to become half-saturated. The appropriate dilution rate for operation in both reactors was the same at 0.75h−1. To effectively produce β-CD, an integrated CSTR-PBR was developed. Through this integrated system, the final β-CD concentration and yield were improved from 6.10gL−1 and 15.3% in a single CSTR up to 10.6gL−1 and 26.5%, respectively. Moreover, the immobilized CGTase had good operational stability for 96h of continuous use. This study has shown that the integrated CSTR-PBR was effective for continuous production of β-CD from starch and may greatly contribute to developing industrialized production of β-CD.