BESC scores a first with isobutanol directly from cellulose

March 7, 2011

In the quest for inexpensive biofuels, cellulose proved no match for a bioprocessing strategy and genetically engineered microbe developed by researchers at the Department of Energy's BioEnergy Science Center.

Using consolidated bioprocessing, a team led by James Liao of the University of California at Los Angeles for the first time produced isobutanol directly from cellulose. The team's work, published online in , represents across-the-board savings in processing costs and time, plus isobutanol is a higher grade of alcohol than .

"Unlike ethanol, isobutanol can be blended at any ratio with and should eliminate the need for dedicated infrastructure in tanks or vehicles," said Liao, chancellor's professor and vice chair of Chemical and Biomolecular Engineering at the UCLA Henry Samueli School of Engineering and Applied Science. "Plus, it may be possible to use isobutanol directly in current engines without modification."

Compared to ethanol, higher alcohols such as isobutanol are better candidates for gasoline replacement because they have an , octane value and Reid vapor pressure – a measurement of volatility – that is much closer to gasoline, Liao said.

While cellulosic biomass like corn stover and switchgrass is abundant and cheap, it is much more difficult to utilize than corn and sugar cane. This is due in large part because of recalcitrance, or a plant's natural defenses to being chemically dismantled.

Adding to the complexity is the fact biofuel production that involves several steps – pretreatment, enzyme treatment and fermentation – is more costly than a method that combines biomass utilization and the fermentation of sugars to biofuel into a single process.

To make the conversion possible, Liao and postdoctoral researcher Wendy Higashide of UCLA and Yongchao Li and Yunfeng Yang of Oak Ridge National Laboratory had to develop a strain of Clostridium celluloyticum, a native cellulose-degrading microbe, that could synthesize isobutanol directly from cellulose.

"This work is based on our earlier work at UCLA in building a synthetic pathway for isobutanol production," Liao said.

While some Clostridium species produce butanol, these organisms typically do not digest cellulose directly. Other Clostridium species digest but do not produce butanol. None produce isobutanol, an isomer of butanol.

"In nature, no microorganisms have been identified that possess all of the characteristics necessary for the ideal consolidated bioprocessing strain, so we knew we had to genetically engineer a strain for this purpose," Li said.

While there were many possible microbial candidates, the research team ultimately chose Clostridium cellulolyticum, which was originally isolated from decayed grass. The researchers noted that their strategy exploits the host's natural cellulolytic activity and the amino acid biosynthetic pathway and diverts its intermediates to produce higher alcohol than ethanol.

The researchers also noted that Clostridium cellulolyticum has been genetically engineered to improve ethanol production, and this has led to additional more detailed research. Clostridium cellulolyticum has a sequenced genome available via DOE's Joint Genome Institute. This proof of concept research sets the stage for studies that will likely involve genetic manipulation of other consolidated bioprocessing microorganisms.

Explore further: Displacing petroleum-derived butanol with plants

More information: The paper is titled "Metabolic Engineering of Clostridium Cellulolyticum for Isobutanol Production from Cellulose," and is available online at aem.asm.org/

Related Stories

Displacing petroleum-derived butanol with plants

January 8, 2009

As a chemical for industrial processes, butanol is used in everything from brake fluid, to paint thinners, to plastics. According to a University of Illinois researcher, butanol made from plant material could displace butanol ...

Researchers Create First Synthetic Cellulosome in Yeast

October 29, 2009

(PhysOrg.com) -- A team of researchers led by University of California, Riverside (UCR) Professor of Chemical Engineering Wilfred Chen has constructed for the first time a synthetic cellulosome in yeast, which is much more ...

Recommended for you

In changing oceans, cephalopods are booming

May 23, 2016

Humans have changed the world's oceans in ways that have been devastating to many marine species. But, according to new evidence, it appears that the change has so far been good for cephalopods, the group including octopuses, ...

A 100-million-year partnership on the brink of extinction

May 24, 2016

A relationship that has lasted for 100 million years is at serious risk of ending, due to the effects of environmental and climate change. A species of spiny crayfish native to Australia and the tiny flatworms that depend ...

Rare evolutionary event detected in the lab

May 23, 2016

It took nearly a half trillion tries before researchers at The University of Texas at Austin witnessed a rare event and perhaps solved an evolutionary puzzle about how introns, non-coding sequences of DNA located within genes, ...

Is aging inevitable? Not necessarily for sea urchins

May 25, 2016

Sea urchins are remarkable organisms. They can quickly regrow damaged spines and feet. Some species also live to extraordinary old ages and—even more remarkably—do so with no signs of poor health, such as a decline in ...

Why fruit fly sperm are giant

May 25, 2016

In the animal kingdom, sperm usually are considerably smaller than eggs, which means that males can produce far more of them. Large numbers of tiny sperm can increase the probability of successful fertilization, especially ...

2 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

bg1
not rated yet Mar 07, 2011
This is important. Isobutanol is not only nearly as energy dense as gasoline, but it is easy to separate from water.
winthrom
not rated yet Mar 07, 2011
Good news. This will keep boaters and airplane owners off leaded gas and still be safe to use.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.