KINETICS OF THE HYDROLYSIS OF CASSAVA STARCH BY GLUCOAMYLASE AND A GRANULAR STARCH HYDROLYZING ENZYME

Abstract

Kinetic studies of the enzymatic hydrolysis of cassava starch have been carried out using glucoamylase and granular starch hydrolyzing enzyme (GSHE) as StargenTM 002. The enzymatic hydrolysis of cassava starch was conducted at pH 4 by employing slurry concentrations of 25-300 g·L-1, temperatures 30-60 C and 0.5-1.5 % (w/w) of enzymes glucoamylase and StargenTM 002. Higher temperatures accelerated the enzymatic reaction using glucoamylase, while the similar effect levelled of at 40 °C for hydrolysis using StargenTM 002. The cassava starch concentrations of 200 and 250 g‧L-1 were found as the critical substrate concentrations for lower (glucoamylase 0.5 and 1 %) and higher (glucoamylase 1.5 %) enzyme concentrations used, respectively. Based on the Lineweaver-Burk plot for cassava starch hydrolysis using glucoamylase, the maximum reaction rates, Vmax for 0.5, 1.0 and 1.5 % (w/w) glucoamylase were 3.55, 5.78 and 9 g‧L-1‧h-1, while the Michaelis-Menten constants, Km were 140.35, 140.75 and 152.10 g‧L-1. Accordingly, the maximum reaction rates, Vmax for 0.5, 1 and 1.5 % (w/w) of StargenTM 002 were 7.19, 11.6 and 18.18 g‧L-1‧h-1, respectively. While the Michaelis-Menten constants, Km obtained at those enzyme concentrations were respectively 160.86, 161.31 and 160.85 g‧L-1. It is an indication that the rate of starch hydrolysis using StargenTM 002 is faster than glucoamylase.

Keywords

• cassava
• enzyme kinetics
• glucoamylase
• GSHE
• hydrolysis