Optimum Conditions and Kinetics of Enzymatic Hydrolysis of Cassava Starch from Flour and Root Chip Powder for Further Studies at the Large-Scale

Abstract

The production of sugar solution i.e. glucose syrup and other related products from hydrolysis of starch is one of the most popular methods. For the efficient use of enzymes in order to obtain maximum product yield, at a large-scale i.e. a pilot scale or an industrial scale, at any designed hydrolytic velocity e.g. a maximum rate, the appropriate amount or concentration of those enzymes used per unit (mass) of starch substrate should be studied following finding the optimum conditions for hydrolysis. Cassava starch from flour and from root chip powder was hydrolysed by alpha-amylase at a concentration of 0.05% w/v at 98 oC for 20 min and at a range of pH and temperature. The highest sugar concentrations were obtained from hydrolysis at 90 oC and pH 6.5 for starch from both sources. At a range of concentration, they were hydrolysed by a fixed volume (15μL) of 0.05% v/v alpha-amylase with the optimum pH of 6.5 and at 90 oC for 10 min. The maximum velocity, Vmax for hydrolysis of flour starch was at 45.78 μg of sugar obtained per min with an Km of 0.51 g of flour per 100 mL of water and that of chip powder was at 32.38 μg/min with an Km of 0.31 g of chip powder per 100 mL of water. They were also hydrolysed by a saccharifying enzyme, glucoamylase at a concentration of 0.14% w/v at a range of pH and temperature for 20 min. The highest sugar concentrations were obtained from hydrolysis, of starch from both sources, at 65 oC and pH 4.5. At a range of concentration, they were also hydrolysed by glucoamylase at a fixed amount of glucoamylase with the optimum pH of 4.5 a 65 oC for 10 min. The Vmax for hydrolysis of flour starch was at 213.78 μg/min with an Km of 0.15 g of flour per 100 mL of water and the Vmax of root chip powder starch hydrolysis was at 202.12 μg/min with an Km of 0.18 g of chip powder per 100 mL of water. These studies can be further applied for large-scale enzymatic hydrolysis of cassava starch.