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α‐Chymotrypsin catalysis in imidazolium‐based ionic liquids
Author(s) -
Laszlo Joseph A.,
Compton David L.
Publication year - 2001
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.1177
Subject(s) - ionic liquid , hexafluorophosphate , chemistry , ethylene glycol , transesterification , supercritical fluid , chymotrypsin , organic chemistry , solvent , catalysis , inorganic chemistry , enzyme , trypsin
The transesterification reaction of N ‐acetyl‐ L ‐phenylalanine ethyl ester with 1‐propanol catalyzed by α‐chymotrypsin was examined in the ionic liquids 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([bmim][PF 6 ]) and 1‐octyl‐3‐methylimidazolium hexafluorophosphate ([omim][PF 6 ]), and in combination with supercritical carbon dioxide (SC‐CO 2 ). The activity of α‐chymotrypsin was studied to determine whether trends in solvent polarity, water activity, and enzyme support properties, observed with this enzyme in conventional organic solvents, hold for the novel environment provided by ionic liquids. α‐Chymotrypsin freeze‐dried with K 2 HPO 4 , KCl, or poly(ethylene glycol) demonstrated no activity in [bmim][PF 6 ] or [omim][PF 6 ] at very low water concentrations, but moderate transesterification rates were observed with the ionic liquids containing 0.25% water (v/v) and higher. However, the physical complexation of the enzyme with poly(ethylene glycol) or KCl did not substantially stimulate activity in the ionic liquids, unlike that observed in hexane or isooctane. Activities were considerably higher in [omim][PF 6 ] than [bmim][PF 6 ]. Added water was not necessary for enzyme activity when ionic liquids were combined with SC‐CO 2 . These results indicate that [bmim][PF 6 ] and [omim][PF 6 ] provide a relatively polar environment, which can be modified with nonpolar SC‐CO 2 to optimize enzyme activity. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 75: 181–186, 2001.