Abstract: The synergistic hydrolysis efficiency of Kudzu starch with α-amylase and glucoamylase was evaluated and a model of enzymatic hydrolysis kinetics was established in our study. The effects of single α-amylase system followed by single glucoamylase system, mixed α-amylase and glucoamylase system, starch granules with different sizes and α-amylase/glucoamylase combination with different ratios on reducing sugar formation were investigated to determine the pattern of starch hydrolysis and the optimal α-amylase/glucoamylase combination. Based on starch granules with different sizes and experimental data as well as previous studies, a modified kinetic model for the hydrolysis of Kudzu starch with the combination of α-amylase and glucoamylase was established. At the same time, the effects of initial concentration of Kudzu starch and different α-amylase/glucoamylase combinations on the model of enzyme kinetics were also investigated in this paper. The kinetic constants were determined and the model was verified through multiple experiments. These results showed a significant difference (P＜0.01) in the rate of reducing sugar formation between single enzyme system and mixed enzyme system. The α-amylase exhibited a high synergistic effect on glucoamylase. The optimal α-amylase/glucoamylase combinations were α-amylase concentration of 20 U and glucoamylase concentration of 36 U. Finally, these results also showed that the model of enzymatic hydrolysis kinetics was valid only if the initial concentration of Kudzu starch was not more than 18.5 mg/mL, and the concentrations of α-amylase and glucoamylase were less than 40 U and 72 U, respectively.

Key words: α-amylase, glucoamylase, synergistic effect, model of enzymatic hydrolysis kinetics