Research in Biofuels Production

E. coli metabolism reversed for speedy production of fuels, chemicals

 

In a biotechnological race, Rice University engineering researchers unveiled a new method for rapidly converting simple glucose into biofuels and petrochemical substitutes. In a paper published online in Nature, Rice's team described how it reversed one of the most efficient of all metabolic pathways—the beta oxidation cycle—to engineer bacteria that produce biofuel at a breakneck pace.

 

On a cell-per-cell basis, the bacteria produced the butanol, a biofuel that can be substituted for gasoline in most engines, about 10 times faster than any previously reported organism -- and this is accomplished using just glucose and mineral salts.

 

The Rice University laboratory is in a race with hundreds of labs around the world to find green methods for producing chemicals like butanol that have historically come from petroleum. These are called "drop-in" fuels and chemicals, because their structure and properties are very similar, sometimes identical, to petroleum-based products. This means they can be dropped in, or substituted, for products that are produced today by the petrochemical industry.

 

Butanol is a relatively short molecule, with a backbone of just four carbon atoms. Molecules with longer carbon chains have been even more troublesome for biotech producers to make, particularly molecules with chains of 10 or more carbon atoms. This is partly because researchers have focused on ramping up the natural metabolic processes that cells use to build long-chain fatty acids. The Rice University lab took a completely different approach.

 

Rather than going with the process nature uses to build fatty acids, they reversed the process that it uses to break them apart. It's definitely unconventional, but it makes sense because the routes nature has selected to build fatty acids are very inefficient compared with the reversal of the route it uses to break them apart.

 

The beta oxidation process is one of biology's most fundamental. Species ranging from single-celled bacteria to human beings use beta oxidation to break down fatty acids and generate energy.

 

In the Nature study, the Rice University team reversed the beta oxidation cycle by selectively manipulating about a dozen genes in the bacteria Escherichia coli. They also showed that selective manipulations of particular genes could be used to produce fatty acids of particular lengths, including long-chain molecules like stearic acid and palmitic acid, which have chains of more than a dozen carbon atoms.

 

The process can be used to make many kinds of specialized molecules for many different markets and it can be done in any organism, since the reverse-beta oxidation pathway is present in almost every organism.

Source: Rice University