| Summary: | Two main processes in Cyclodextrins (CDs) production were studied in order to
improve the industrial production. These processes are the enzymatic reaction
of Cyclodextrin Glycosyl Transferase (CGTase) on starch which produces a
mixture of CDs and other by-products, and the adsorption process on the
enzymatic product mixture to obtain single CD. The CGTase enzymatic
reactions on various starches were investigated by batch mode and dynamic
mathematical modelling was proposed.
Tapioca starch shows the highest CDs production of 23 g L-1 followed by sago
(22 g L-1) and corn (19 g L-1) starch using 5% (w/v) initial starch concentration.
From the experimental data of tapioca starch, Michaelis-Menten parameter
which is also known as substrate limitation parameter, KM (58.23, 54.07 and
7.52 g L-1 for α-, β- and ɣ-CD, respectively) and maximum velocity of enzymatic
kinetic, Vmax (3.45, 2.76 and 0.45 g L-1 min-1 for α-, β- and ɣ-CD, respectively)
were obtained by linearization. Results show that the production of CDs was
also affected by product inhibition, K1,i at the range of 9 to 0.8 g L-1 and
degradation of CD rate by coupling reaction, CD,i at the range of 0.0046 to
0.658 min-1. Thus, all parameters were considered using the dynamic
simulation and found that the exponential reaction kinetic model fitted the
experimental data better. Results were supported by sensitivity analysis on K1,i
parameter with impact of 8 – 18% difference from original data and validation
experiment by using fed batch mode.
In adsorption process, experimental results show the highest adsorption of α-
CDs (700 mg g-1) was at low temperature (20˚C) and as temperature increase
up to 50˚C, the adsorption of α-CDs reduce until 400 mg g-1. Fractogel EMDPhenyl
retained α-CD as temperature increase from 20 until 50˚C, thus can be
separated from β- and ɣ-CD. Adsorption of CDs onto Fractogel EMD-Phenyl
adsorbent was preferred when compared to activated carbon (AC). The kinetic
and isotherm adsorption studies were done by fitting the adsorption data with
several models. The kinetic adsorption of CDs onto Fractogel EMD-Phenyl could be described by the pseudo-second-order kinetics model with R2 value of
> 0.94 and SSE value < 28. The adsorption equilibrium data obeys the Temkin
isotherm model with R2 value of > 0.84 and SSE value was less than 30.23.
The adsorption activation energies obtained were at the range of 3 - 40 kJ
mol-1.
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