Premium
Criteria to Design Green Enzymatic Processes in Ionic Liquid/Supercritical Carbon Dioxide Systems
Author(s) -
Lozano Pedro,
de Diego Teresa,
Gmouh Said,
Vaultier Michel,
Iborra José L.
Publication year - 2004
Publication title -
biotechnology progress
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.572
H-Index - 129
eISSN - 1520-6033
pISSN - 8756-7938
DOI - 10.1021/bp0342497
Subject(s) - chemistry , supercritical carbon dioxide , propionate , ionic liquid , candida antarctica , kinetic resolution , catalysis , solubility , alkyl , organic chemistry , supercritical fluid , ammonium bromide , enantioselective synthesis , enzyme , lipase , pulmonary surfactant , biochemistry
Five different ionic liquids (ILs) based on quaternary ammonium cations, with functional side chains ((3‐hydroxypropyl)‐trimethyl‐, (3‐cyanopropyl)‐trimethyl‐, butyl‐trimethyl‐, (5‐cyanopentyl)‐trimethyl‐ and hexyl‐trimethyl‐) associated with the same anion (bis(trifluoromethane)sulfonyl amide)), were synthesized, and their suitability for Candida antarctica lipase B (CALB)‐catalyzed ester synthesis in IL/supercritical carbon dioxide (scCO 2 ) biphasic systems was assayed. Catalytic efficiency of the system has been analyzed as a function of both enzyme properties and mass‐transfer phenomena criteria. First, the suitability of these ILs as enzymic reaction media was tested for the kinetic resolution of rac ‐phenylethanol. All ILs were found to be suitable media for enzyme catalysis, the best catalytic parameter (5.3 U/mg specific activity, 94.9% selectivity) being obtained for the (5‐cyanopentyl)‐trimethylammonium. Second, enzyme stability in all of the ILs was studied at 50 °C over a period of 50 days, and data were analyzed by a two‐step kinetic deactivation model. All of the ILs were shown to act as stabilizing agents with respect to hexane, producing an increase in the free energy of deactivation (to 25 kJ/mol protein) and an improvement in the half‐life time of the enzyme (2000‐fold), which agrees with the observed increased hydrophobicity of the cation alkyl side chain (measured by Hansenapos;s solubility parameter, δ). By using two different CALB‐IL systems with different hydrophobicity in the cation, continuous processes to synthesize six different short chain alkyl esters (butyl acetate, butyl propionate, butyl butyrate, hexyl propionate, hexyl butyrate, and octyl propionate) in scCO 2 at 10 MPa and 50 °C were carried out. Both rate‐limiting parameters (synthetic activity and scCO 2 –ILs mass‐transfer phenomena) were related with the δ‐parameter of the ILs‐alkyl chain and reagents.