40
M.J. Eisenmenger, J.I. Reyes-De-Corcuera / Journal of Molecular Catalysis B: Enzymatic 67 (2010) 36–40
range was narrow, it covered most commonly used enzyme reac-
tion conditions. Up to 25-fold CALB activity increase was attributed
to increased HHP for the synthesis of isoamyl acetate. The conver-
sion of isoamyl alcohol and acetic acid to isoamyl acetate in an
RTIL–alcohol biphasic system is 10 times more efficient with free
than with immobilized lipase. Also, rate of conversion was higher at
elevated pressure for both free and immobilized lipase. High pres-
sure had no significant effect on the activation energy of free lipase
and temperature had no significant effect on the activation vol-
ume, which was negative throughout the pressure range tested.
Free lipase is better suited than immobilized lipase in this system
which will allow future studies to proceed more effectively. Lastly,
the observation of the temporary immobilization phenomenon is
a new and previously undocumented occurrence. This unique phe-
nomenon may aid in recycling during a batch process by increasing
the ease of decanting procedures while minimizing enzyme and
RTIL loss.
Fig. 7. Linearized effect of pressure on initial rate at (ꢀ) 40 ◦C and (ꢀ) 80 ◦C.
from the slope of the plots shown in Fig. 7. The ꢀV‡ was negative
results are different than in hexane where the negative ꢀV‡ of CALB
catalyzed isoamyl acetate synthesis in hexane was decreased by
increasing temperature from −21.6 2.9 at 40 ◦C to −12.9 1.7 at
80 ◦C [20]. This study found a negative ꢀV‡ throughout the entire
pressure range tested (0.1–500 MPa) which is in contrast to CALB in
hexane that found a negative ꢀV‡ from 0.1 to 200 MPa and positive
ꢀV‡ from 300 to 500 MPa. These differences between temperature
affects on ꢀV‡ indicate that the solvent (either hexane or RTIL) has
Acknowledgement
This project was supported by a Research Innovation Grant from
the University of Florida Institute of Food and Agricultural Sciences.
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