Iowa State Researchers Redesigning Enzyme for Bio-based Production of Isobutene (updated)
24 June 2010
Thomas Bobik, professor of biochemistry, biophysics and molecular biology at Iowa State University is heading an effort to redesign an enzyme for the bio-based production of isobutene, a gas that is currently used in the production of a variety of chemicals and in the manufacture of other fuel additives, adhesive, plastics and synthetic rubber. Isobutene can be converted to isooctane, used in gasoline.
| Global Bioenergies |
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| Global Bioenergies, a French startup that has developed a synthetic metabolic pathway for producing isobutene (earlier post), earlier this year received €760,000 (US$940,000) in funding from the French innovation agency OSEO to accelerate the development of its process. |
| Global Bioenergies says that its gaseous bioproduction of isobutene relies on establishing an artificial metabolic pathway in a variety of microbes. |
| It can be adapted for the conversion of various resources: sugar cane or sugar beet, glucose from cereal starch or sugars generated by the digestion of lignocellulosic material (agricultural or forestry waste). |
Isobutene is typically produced from nonrenewable petroleum-based feedstocks by either steam cracking of naphtha or fluid catalytic cracking of gas oil. These processes can be energy intensive, and can require harsh reaction conditions and corrosive chemicals as well as purification steps to separate isomers of isobutene (e.g., 1-butene).
The redesigned enzyme catalyzes the conversion of 3-hydroxy-3-methylbutrate (3-HMB) to isobutene; through directed enzyme evolution, Bobik has increased the production of isobutene 20-to 40-fold over the wild type enzyme.
3-HMB can be produced from glucose, biomass and other renewable feedstocks; therefore, this enzyme represents a promising avenue for biobased production of isobutene.
Biological production of isobutene may also overcome the drawback of yield limitations seen in instances where renewable products are toxic to producer cells; since isobutene is a gas, it may be able to be easily removed from a fermentation vessel before it can accumulate to potentially inhibitory levels. Removal of isobutene in the gas phase may also facilitate its separation and purification and lower production costs.
In addition, the enzyme may be able to catalyze the conversion of other 3-hydroxy acids to alpha-olefins, which are also important industrial chemicals.
The base enzyme is found naturally in about half of all organisms in the world, Bobik said. While patent applications proceed, Bobik will not disclose the specific enzyme.
The activity of the enzyme is low. It’s too low for commercial application. So we’re trying to use directed enzyme evolution to improve the activity of the enzyme.
—Thomas Bobik
Next time one goes hungry, eat your car seats and drink the ethanol in your fuel tank!
Posted by: HarveyD | 24 June 2010 at 07:49 AM