Researchers at UCLA’s Henry Samueli School
of Engineering and Applied Science have developed a way to produce normal butanol
from bacteria at rates significantly higher than those achieved using current
production methods.
The findings, reported online in Applied and Environmental Microbiology,
mark an important advance in the production of normal butanol, or n-butanol, a
four-carbon chain alcohol that has been shown to work well with existing energy
infrastructure, including in vehicles designed for gasoline, without
modifications that would be required with other biofuels.
The UCLA team, led by James C. Liao, UCLA’s
Chancellor’s Professor of Chemical and Biomolecular Engineering, demonstrated
success in producing 15 to 30 grams of n-butanol per liter of culture medium
using genetically engineered Escherichia
coli—a record-setting increase over the typical one to four grams
produced per liter in the past.
For the study, Liao and his team initially
constructed an n-butanol biochemical pathway in E. coli, a microbe that doesn’t naturally produce
n-butanol, but found that production levels were limited. However, after adding
metabolic driving forces to the pathway, the researchers witnessed a tenfold
increase in the production of n-butanol. The metabolic driving forces pushed
the carbon flux to n-butanol.
“Like human beings, microbes need an
incentive to work,” said Liao, the study’s senior author.
“We created driving forces by
genetically engineering the metabolism,” said Claire R. Shen, a UCLA
Engineering graduate student and lead author of the study.
While certain microbes, including species of
the bacteria Clostridium,
naturally produce n-butanol, Liao’s team used E. coli because it is easier to manipulate and has been
used industrially in producing various chemicals.
“By using E. coli, we can make it produce only the compound with no
other byproducts,” Liao said. “With native producing organisms like Clostridium, which naturally produces
n-butanol, there are other byproducts that would add cost to the separation
process.”
The next step in the research, the
researchers say, will be to transfer the study to industry for the development
of a more robust industrial process.
