Mathematical modelling and kinetic study for CD production catalysed by Toruzyme® and CGTase from Bacillus firmus strain 37.
The process of producing cyclodextrins from starch with cyclodextrin glucanotransferase from Bacillus megaterium has been studied. The effect of starch and enzyme concentrations was evaluated using optimal composite designs and the response surface methodology. Mathematical models describing the process in two overlapping areas of variation of the independent variables were developed. The models were used to determine the optimal values of the variables. The increase in starch concentration resulted in an increase in the amount of b-cyclodextrin formed, but lowered the yield. The optimal starch concentration was considered to be 50.0 mg/mL. The critical cyclodextrin glucanotransferase concentration necessary for maximum b-cyclodextrin production was 2.0 U/g. Factors that limit the complete conversion of starch to cyclodextrins were established. The enzyme activity was strongly inhibited by the reaction products. The coupling activity of cyclodextrin glucanotransferase was proved. The enzyme was able to degrade high concentrations of b-cyclodextrin and to transform different types of cyclodextrins one into another. Cyclodextrin glucanotransferase formed a-, band g-cyclodextrins in different ratios, depending on the duration of the process.