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Please use this identifier to cite or link to this item: http://hdl.handle.net/1812/492

Title: Optimization of enzyme -mediated sogo starch hydrolysis using response surface methdology
Authors: Lai, Long wee
Keywords: Aspergillus niger
Sago starch
sugars
Response surface methodology
Central composite design
Issue Date: Nov-2008
Publisher: University of Malaya
Abstract: Aspergillus niger glucoamylase (E.C. 3.2.1.3) was used to hydrolyze sago starch into reducing sugars. The quantitative effects, namely: pH, temperature, agitation speed, substrate concentration and enzyme amount were investigated in order to optimize initial reaction velocity, v and yield of reducing sugars, Yp/s using a response surface methodology (RSM) central composite design (CCD) protocol. The effect of process parameters were monitored in a two liter (2.0 L) stirred tank reactor to study the maximum conversion efficiency of sago starch into reducing sugars by the use of this enzyme. The maximum initial reaction velocity of 0.50 mmoles.L-1.min-1 and sugars yield of 0.58 g g-1 were predicted at a temperature of 61 oC, substrate concentration of 1.0 g.L-1, enzyme amount 0.2 U.ml-1 when the pH and agitation speed were fixed at 4.5 and 100 rpm, respectively. The effects of pH and agitation speed were found to be statistically insignificant in this research. The subsequent validation experiments confirmed the optimal values of the process parameters with v = 0.51 } 0.07 mmoles.L-1.min-1 and Yp/s = 0.60 } 0.08 g g-1. Thus by using the CCD of RSM, it is possible to determine the optimal setting values of the process parameters where maximum initial reaction velocity and highest production of reducing sugars occur. On the other hand, the kinetic parameters (Km and Vmax) obtained using Langmuir linearization method were in close agreement with non-linear regression where both values of Km and Vmax were 13.52 mM; 2.35 mmoles.L-1.min-1 and 12.91 mM; 2.36 mmoles.L-1.min-1, respectively. The _H and _S estimated via van’t Hoff analysis were 7.86 J.mole-1 and 6.15 J.mole-1.K-1, respectively. The results indicated that the hydrolysis process is an endothermic reaction and spontaneous. This is also supported by the negative sign of _G which indicates that the enzymatic sago starch hydrolysis reaction is spontaneous within experimental temperature range of 30 – 60 oC. It is calculated that 26.3 J.mole-1 of activation energy, Ea is required for the enzymatic conversion of sago starch into reducing sugars. A mathematical model based on Michaelis-Menten kinetic was used to simulate the sago starch hydrolysis process. The model prediction agrees well with experimental data.
Description: Dissertation (M.Sc.) -- Faculty of Science, University of Malaya, 2008.
URI: http://dspace.fsktm.um.edu.my/handle/1812/492
Appears in Collections:Masters Dissertations : Science

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