Experimental studies and kinetic modeling of cyclodextrin glucanotransferase production from starch with the use ofBacillussp. DSM 2523

Abstract

Cyclodextrin glucanotransferase (CGTase) production from starch with the use of Bacillus sp. DSM 2523 was studied. The specific growth rate (µ) considering the initial starch concentrations (S0) ranging from 0.2% to 2% w/v, was determined and a maximum value for µ of 0.1151/h was found at S0 = 0.5% w/v. The maximum specific CGTase production rate (qP) at S0 = 0.2% w/v, was 1.1105/h with considerable fluctuations in enzyme production. By performing a repeated batch experiment using dextrin as feeding substrate, the cell's ability to maintain its responses for an extended period of time was examined. The trend toward a decrease in the µ value and qP with an increase in the substrate concentration was evident. The experimental data showing the inhibitory function of starch on the growth and enzyme production were best predicted using Haldane model. On basis of the cell maintenance concept the observed dependency of the growth yield (Y) on the starch concentration was applied and the relationship between maintenance energy and µ was evaluated. At concentrations of starch below 0.5% w/v, the constant maintenance energy can be obtained. The variation of maintenance energy dependency on µ was assessed in the inhibited culture system (S0 ≥ 0.5% w/v).