Abstract
The kinetics and inhibitory effects of cyanide on the granular starch hydrolyzing enzyme (GSHE) activity during hydrolysis of cassava (Manihot esculenta Crantz) starch at low temperature were studied. The substrates included native cassava starch at various concentrations (100-400 g/L) and native cassava starches with added cyanide at various concentrations (50-150 mg/kg), while the concentration of enzyme was 1.5% (w/w). A decrease in reducing sugar concentration during hydrolysis of cassava starch indicated that the cyanide reduced the enzyme activity. Lineweaver-Burk plot of Michaelis-Menten equation was used to study the inhibition kinetics. The maximum velocity (Vmax) value was higher for native cassava starch than that of native cassava starch with added cyanides. The presence of cyanide was found to reduce the Vmax values. No significant different of the saturation constant (Km) value between native cassava starch and native cassava starch with added cyanides was observed. Based on the inhibition type analysis, the effect of cyanide in the cassava starch can be classified as a noncompetitive inhibition, with the Ki value of 0.33 mg/L.
Highlights
Cassava is a high-yielding crop that can grow well in the tropical and subtropical regions, such Africa, South America, India and Southeast Asia
A decrease in reducing sugar concentration during hydrolysis of cassava starch indicated that the cyanide reduced the enzyme activity
Granular starch hydrolyzing enzyme as StargenTM 002, contains Aspergillus kawachi alpha-amylase expressed in Trichoderma reesei and a glucoamylase from Trichoderma reesei that work synergistically to hydrolyze granular starch substrate to glucose was produced by Genencor (Palo Alto, USA)
Summary
Cassava is a high-yielding crop that can grow well in the tropical and subtropical regions, such Africa, South America, India and Southeast Asia. Cassava has many superior growing characteristics over the other crops that include high drought and flood-tolerance and ability to grow on light sandy soils and medium texture soils [1]. Another advantage of cassava is related to its higher starch content than many other stem tuber plants. Cassava starch can be converted into glucose syrup (for food applications) and to ethanol (for fuel application) through hydrolysis and fermentation processes. Based on its starch content, it is estimated that 7.2 tons of fresh cassava can produce 1.9570 ton of glucose or 1 ton of ethanol [2]
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