Enhanced synthesis of isoamyl acetate using an ionic liquid-alcohol biphasic system at high hydrostatic pressure

Isoamyl acetate has a banana flavor that can be considered a "natural" ingredient when synthesized using a lipase-catalyzed reaction. Production of isoamyl acetate was up to 10-fold higher with free lipase versus immobilized Candida antarctica lipase B (CALB) after 3h at 300 MPa and 80 degrees C in 1-butyl-3-methylimidazolium hexafluoro-phosphate, isoamyl alcohol biphasic system. Rate of catalysis by free CALB was 15-fold greater at 500 MPa, 40 degrees C than at 0.1 MPa, 40 degrees C and 14-fold at 500 MPa, 80 degrees C than at 0.1 MPa, 80 degrees C. Activation energy of free lipase calculated between 40 and 80 degrees C at 0.1 MPa (55.6 +/- 4.2 kJ mol(-1)) or 300 MPa (56.2 +/- 4.6 kJ mol(-1)) was not significantly different. Similarly, activation volume (Delta V double dagger) of free lipase calculated between 0.1 and 500 MPa at 40 degrees C (-16.1 +/- 1.5 cm(3) mol(-1)) or 80 degrees C (-16.7 +/- 1.4 cm(3) mol(-1)) was not significantly different. After treatment at high pressure and upon pressure release, the free lipase was temporarily suspended in a semi-solid IL phase. This study is the first to combine the use of a room temperature ionic liquid (RTIL) and high hydrostatic pressure (HHP) for enhanced enzyme catalysis. (C) 2010 Elsevier B.V. All rights reserved.