Submitted to: Journal of Molecular Catalysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 27, 2002
Publication Date: N/A
Interpretive Summary: Our intent is to find ways to use enzymes to create new or value-added products from vegetable oils and related lipids. Many of the enzymes that make valuable transformations of lipids are heme-containing proteins. (Hemoglobin is an example of a heme-containing protein, but it does not make useful lipid transformations.) The really useful enzymes tend to be expensive, difficult to isolate, and not particularly stable once isolated. We therefore investigated whether simpler, more practical enzymes can be substituted for cantankerous ones, if placed in the right environment. We examined three such simple enzymes in a new media called ionic liquids. These simple enzymes performed quite well in these media. Our research indicates that we can employ rudimentary enzymes in ionic liquids to make practical modifications to lipids. This finding will direct our efforts to produce high-value products from commodity plant lipids.
Technical Abstract: The ability of ferriprotoporphyrin(IX) chloride (hemin), microperoxidase-11 (MP-11), and cytochrome c (cyt-c) to oxidize guaiacol (2-methoxyphenol) was examined in the room-temperature ionic liquids (IL) 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide and the hexafluorophosphates of 1-butyl- and 1-octyl-3-methylimidazolium. All three biocatalysts displayed peroxidase activity when activated by an electron acceptor, tert-butyl hydroperoxide for hemin and hydrogen peroxide for MP-11 and cyt-c. Hemin required the addition of a coordinating base, N-methylimidazole or pyridine, to produce an active complex. Cyt-c did not require exogenous ligands for activity in IL, although their addition increased peroxidase activity. Hemin and MP-11 peroxidase activities were markedly higher in IL compared to molecular solvents of similar polarity (methanol and dimethylsulfoxide), while cyt-c activity was comparable between both types of solvents. There was no consistent preference by the three peroxidase catalysts for a particular IL. These observations indicate that IL are suitable media for bioelectrocatalysis.