(610e) Optimizing Immobilized Enzyme Performance in Cell-Free Environments to Produce Liquid Fuels

2012 AIChE Annual Meeting: Cleaner
Energy, Stronger Economy, Better Living

Pittsburg, PA

Fuels and Petrochemicals
Division

20002 Alternative Fuels I (Oral
Talk)

October 28^th -
November 2^nd, 2012

Optimizing immobilized enzyme performance in

cell-free environments to produce liquid fuels

Joseph J. Grimaldi, Cynthia H. Collins and Georges
Belfort

Howard P Isermann Department of Chemical and
Biological Engineering, and

Center of Biotechnology and Interdisciplinary Studies

Rensselaer Polytechnic Institute, Troy, NY 12180-3590

Active research to
produce energy via biofuel from cells, or through the bioconversion of sugars
to liquid fuels, offers exciting new alternates to fossil fuel.  We focus on the bioconversion of ketoisovaleric
acid, a derivative of sugar, to iso-butanol using a
two-enzyme system.  While these
enzymatic routes offer great promise and excellent selectivity for the
production of biofuels, enzymes exhibit slow kinetics, low volume capacity in
solution, and product feedback inhibition. 
These limitations must be overcome so that biofuels can be produced
economically.  We utilize a novel
approach to address these limitations. 
Here, enzymes are first synthesized via recombinant DNA technology and
then immobilized on solid substrates. 
This cell-free enzyme system will be coupled with membrane separations
to continuously remove the desired iso-butanol and
reduce feed-back inhibition.  A model immobilized
enzyme, beta-galactosidase, with a simple color change for assessing
reactivity, was first studied to determine the optimal substrate geometry (flat,
convex, or concave).  Preliminary
data indicates that crowding and orientation of the immobilized enzymes have a
large effect on enzyme kinetics. Serial reactions of immobilized keto-acid decarboxylase and alcohol dehydrogenase to
produce butanol ex-vivo was then
evaluated in solution and bound to substrates.  Finally, The effect of iso-butanol on the kinetics of the enzymes, both in
solution and immobilized, was evaluated.