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

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