Abstract:
The overall aim of this research project was to study kinetic model of cyclodextrin glycosyltransferase (CGTase) production from tapioca starch by Bacillus circulans ATCC 9995. The study consists of three main parts. The first part was to investigate suitable cultivating conditions for the production of CGTase. High cell growth and CGTase production were observed under uncontrolled pH conditions (initial pH of 8), 0.5%w/v CaCO₃, and agitation speed of 400 rpm. The second part was to determine mathematical model that is most suitable in explaining kinetics of CGTase production based ob batch cultivation data from experiments with varied initial starch concentrations from 1.46 to 8.2 g/l. Mosers model µ[subscript m] S[superscript n] / K[superscript n] [subscript h] + S[superscript n] was found to give the best goodness of fit with parameters µ[subscript max], K[subscript h], and n of 0.32 hr⁻₁, 1.98 g/l, and 2, respectively. Average kinetics parameters, Y[subscript X/S,G,avg], Y[subscript P/X,avg], m[subscript S,avg] (maintenance energy requirement) and b[subscript avg] (nongrowth-associated product constant), were also experimentally determined at .067 g-cell/g-starch, 555.97 unit/g-cell, 0.005 g-starch/g-cellhr, and 3.66 unit/g-cellhr respectively. The final part of the project dealt with comparison of simulation result from Mosers model and data obtained from batch experiments. It was found that Mosers model calculated using average kinetic parameter gave good prediction with initial starch concentrations from 6.57 to 11.33 g/l. However, better prediction could be obtained using kinetic parameter obtained directly from each batch data. Simulation of Mosers model in continuous operation for CGTase production by B circulans ATCC 9995 from tapioca starch at dilution rate of 0.24 hr⁻₁ and feed starch concentration of 8.2 g/l showed the maximum cell and CGTase productivity of 0.71 g/lhr and 327.17 unit/lhr, respectively. It was, moreover, found that continuous operation gave threefold higher productivity that batch operation.