Protein coding sequences/Biosynthesis/Butanol

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The following is excerpted from a report by Douglas Ridgway, Project CyberCell, Institute for Biomolecular Design, University of Alberta, April 12, 2007: [http://2007.igem.org/Alberta/background]

Butanol is a superior to ethanol as a replacement for petroleum gasoline. With a low vapor pressure, high energy density, and a gasoline-like octane rating, it can be blended into existing gasoline at much higher proportions than ethanol without compromising performance, mileage, cold starting, or volatile organic pollution standards, without modifying the fuel-air ratio, and without changing the fuel system. More importantly, butanol, like gasoline, is immiscible with water, and less corrosive than ethanol, allowing the existing gasoline infrastructure of tanks and pipelines to be used unmodified. Butanol would thus be a superior liquid fuel, if only it could be produced in a cheap and sustainable manner.

Although fermentation of biomass to butanol has a short history compared to ethanol, having been discovered in the late 19th century, it has nevertheless been proven on large industrial scales. The acetone-butanol (AB) fermentation, based around solventogenic organisms such as Clostridium acetobutylicum, produces acetone, butanol and ethanol from starches, sugars, and cellulose. First developed on a large scale during World War I, when Britain had a high demand for acetone to make cordite, the AB fermentation became the primary process for world butanol production until lower-cost petroleum-derived butanol began to take over in the 1950’s. The AB fermentation has therefore had many decades of optimization on an industrial scale. During this period, a wide variety of solventogenic bacteria have been discovered and characterized, the plant processes developed, and the potential substates identified. Currently, only China still produces butanol via AB fermentation, supplying 50% of internal butanol demand, but this is changing. Increases in petroleum prices, and concerns about sustainability and carbon emissions have revived interest in biobutanol, both from a research perspective and for commercialization. Biobutanol has several advantages over ethanol as a biofuel. One is feedstock flexibility. Solventogenic Clostridia are known to metabolize a wide range of substrates, including hexose and pentose sugars, and naturally produce cellulolytic enzymes, making cellulosic butanol production a substantially simpler proposition than cellulosic ethanol. Butanol has market advantages over ethanol as well. In addition to being a superior gasoline replacement, butanol is used as an industrial solvent in glue and paint production. This non-fuel butanol market currently pays $1-2/l, substantially above the value of ethanol, and would likely be the first market displaced by biobutanol. Butanol as a fuel additive also possesses a coblend synergy with ethanol, allowing larger amounts of ethanol oxygenate in a gasoline blend without exceeding vapor pressure limits. This would eliminate the need for special “summer” and “winter” gasoline formulations, of particular importance to Alberta. Thus butanol has an economic value exceeding that of the energy content alone, easing commercialization.

The market is becoming increasingly aware of biobutanol’s advantages. As one example, a joint project of BP, DuPont, and British Sugar announced in 2006 will convert the East Anglia UK bioethanol plant to butanol production, working from sugar beet feedstock. Other biofuel efforts include those of Amyris Biotechnologies, whose non-ethanol gasoline replacement has not been disclosed, but has technical characteristics similar to butanol. Based on the considerations above and the response of the marketplace, it would appear that butanol production from biomass is commercially viable today, without additional technological improvements.

*More...*
Name	Description	Length	Status
BBa_I725011	B-hydroxy butyryl coA dehydrogenase	870	It's complicated
BBa_I72512	Enoyl-coa hydratase	801	It's complicated
BBa_I725013	Butyryl CoA dehyrogenase	1155	It's complicated
BBa_I725014	Butyraldehyde dehydrogenase	2598	It's complicated
BBa_I725015	Butanol dehydrogenase	1188	It's complicated

Erin Dul and the [http://2007.igem.org/Alberta 2007 University of Alberta iGEM team] designed a set of parts for butanol production.