Abstract: To improve enzyme catalytic efficiency, the ionic liquid/buffer biphasic system was used as bio-catalytic medium in catalytic hydrolysis of alliin to the sulfur-containing compounds by alliinase. The results showed that the enzyme activity was higher for 25% ［BMIM］PF₆/ buffer biphasic system than for pure buffer system but inhibited markedly by excess amount of ［BMIM］PF₆,and the thermal stability of the enzyme was enhanced. Using natural alliin as substrate,the K_m of 0.591 mmol·L^-1 and the V_max of 0.316 mmol·L^-1·min^-1 were obtained for the enzyme catalytic reaction in ［BMIM］PF₆/buffer biphasic system,and the V_max/K_m ratio was about 2 fold of buffer monophasic system. In addition,in order to rising yield of essential oil,a combination technique of ionic liquid ［BMIM］PF₆,as bio-catalytic medium and extraction agent,and ultrasound-microwave-assisted was used for preparation and extraction of onion essential oil. The optimized conditions established were as follows:［BMIM］PF₆ concentration 20%(vol),enzymatic time 2 h,ratio of raw material to liquid 1∶1.5,extraction temperature and time 25℃ and 50 s,and ultrasound-microwave power 150 W.Total 22 substances were identified in the onion essential oil prepared from fresh onion and 19 kinds of them sulfur-containing compounds by GC-MS analysis.To improve enzyme catalytic efficiency, the ionic liquid/buffer biphasic system was used as bio-catalytic medium in catalytic hydrolysis of alliin to the sulfur-containing compounds by alliinase. The results showed that the enzyme activity was higher for 25% ［BMIM］PF₆/ buffer biphasic system than for pure buffer system but inhibited markedly by excess amount of ［BMIM］PF₆,and the thermal stability of the enzyme was enhanced. Using natural alliin as substrate,the K_m of 0.591 mmol·L^-1 and the V_max of 0.316 mmol·L^-1·min^-1 were obtained for the enzyme catalytic reaction in ［BMIM］PF₆/buffer biphasic system,and the V_max/K_m ratio was about 2 fold of buffer monophasic system. In addition,in order to rising yield of essential oil,a combination technique of ionic liquid ［BMIM］PF₆,as bio-catalytic medium and extraction agent,and ultrasound-microwave-assisted was used for preparation and extraction of onion essential oil. The optimized conditions established were as follows:［BMIM］PF₆ concentration 20%(vol),enzymatic time 2 h,ratio of raw material to liquid 1∶1.5,extraction temperature and time 25℃ and 50 s,and ultrasound-microwave power 150 W.Total 22 substances were identified in the onion essential oil prepared from fresh onion and 19 kinds of them sulfur-containing compounds by GC-MS analysis.

Key words: ionic liquid, ［BMIM］PF₆, ultrasound-microwave-assisted extraction technique, alliinase, onion essential oil

摘要： 以离子液体［BMIM〖DK〗］PF₆作为生物催化介质，结果显示洋葱蒜氨酸酶在含25%［BMIM］PF₆催化体系中的活性比在纯缓冲液介质中明显要高，对高温变性作用的抵抗能力也相应增强，但若离子液体浓度过高会对酶催化作用的发挥产生阻碍。以洋葱蒜氨酸为底物，测得离子液体［BMIM］PF₆/缓冲液两相体系中蒜氨酸酶的米氏常数为0.591 mmol·L^-1，最大反应速率为0.316 mmol·L^-1·min^-1，V_max/K_m约为缓冲液单相体系中的两倍。实验还尝试发挥疏水性离子液体［BMIM］PF₆作为生物催化介质和萃取剂的双重功能，并将其与超声-微波协同萃取技术相结合应用于洋葱精油制取的酶解和萃取过程，明显提高了酶解效率和精油得率，将制得的精油经GC-MS分析，共鉴定出22种物质，其中19种为含硫化合物。

关键词: 离子液体, ［BMIM］PF₆, 超声-微波, 蒜氨酸酶, 洋葱精油