为了解辐照改性马铃薯淀粉的酶解特性, 用α-淀粉酶和糖化酶同时作用于马铃薯原淀粉和经400 kGy剂量辐照处理后淀粉, 考察了pH值、酶解温度、α-淀粉酶用量、糖化酶用量对反应速率的影响。以米氏方程为基础, 用Lineweaver-Burk法求解动力学参数。结果表明, 辐照后马铃薯淀粉的酶解反应速率明显高于马铃薯原淀粉。在单一水解体系中, α-淀粉酶和糖化酶对辐照前后马铃薯淀粉的降解都遵循Michaelis-Menten方程, α-淀粉酶的Km分别为11.343 mg·mL-1和9.386 mg·mL-1, Vmax分别为0.406 mg(mL·min)-1和1.079 mg(mL·min)-1; 糖化酶的Km分别为10.307 mg·mL-1和8.905 mg·mL-1, Vmax分别为0.338 mg(mL·min)-1和0.821 mg(mL·min)-1; 水解产物葡萄糖对反应体系具有竞争性抑制剂的作用, 其抑制常数Ki分别为1.298 mg·mL-1和0.934 mg·mL-1。研究结果表明辐照有效提高了马铃薯淀粉的酶解反应活性。

In order to understand the enzymatic hydrolysis characteristics of irradiated potato starch, potato native starch and potato starch treated with 60Co-γ ray at dosage of 400 kGy were hydrolyzed by α-amylase and glucoamylase. The effects of pH, hydrolysis temperature and enzyme dosage on hydrolysis rate were investigated. Based on the Michaelis-Menten equation, the kinetic parameters were obtained by the Lineweaver-Burk method. The results indicated that hydrolysis rate of irradiated potato starch was obviously higher than that of native starch. Individual enzymatic hydrolysis processes obeyed the Michaelis-Menten model, and the Michaeli constant (Km) of α-amylase were 11.343 mg·mL-1 (native starch) and 9.386 mg·mL-1 (irradiated starch), and maximum reaction velocity (Vmax)of α-amylase were 0.406 mg(mL·min)-1 (native starch) and 1.079 mg(mL·min)-1 (irradiated starch), respectively. The Michaeli constant (Km)of glucoamylase were 10.307 mg·mL-1 (native starch) and 8.905mg·mL-1 (irradiated starch), and maximum reaction velocity (Vmax) of glucoamylase were 0.338 mg(mL·min)-1 (native starch) and 0.821 mg(mL·min)-1 (irradiated starch), respectively. The hydrolysis product glucose was a competitive inhibitor against the enzymes with an inhibitory constant (Ki) of 1.298 mg·mL-1 (native starch) and 0.934 mg·mL-1 (irradiated starch). It indicated that irradiation greatly increased enzymatic hydrolysis activity of potato starch.