JBEI to assess feasibility of biofuel microbes

By Erin Voegele
Researchers at the Joint BioEnergy Institute, a California-based scientific partnership led by Lawrence Berkeley National Laboratory, have developed a new technique to complete metabolic studies that could greatly accelerate the search for new biofuel microbes.

To date, this research has focused on the microbe Geobacillus thermoglucosidasius. According to Rajat Sapra, JBEI's director of enzyme optimization and a staff scientist at Sandia National Laboratory, work has focused on this particular microbe for three reasons; it is a bacteria that can grow at high temperatures, it can utilize both C5 and C6 sugars, and it has been shown to have a higher tolerance to ethanol than any other known bacteria.

Sapra said the problem with using classical microbiology techniques to identify potential microbes, such as Geobacillus thermoglucosidasius, for biofuel production is that it is costly and time consuming. "The problem is that if you go down the road of classical microbiology, you have to do genome sequencing, you have to understand the organism's basic metabolism, and that can be a cost or an impediment to its development as a new host for fuel production," he said.

The goal of Sapra's research was to devise a cheaper, less time-consuming alternative to genome sequencing that can be used to determine if a microbe holds potential for biofuel production. "The ideas to devise a method, or adapt a method, or figure out a method that can give us the answers we are looking for," he said. "First of all, can the [microbe] utilize both C5 and C6 sugars? If it can, what are the end products that it is producing, and more importantly, can we figure out the pathways without going down the road of genome sequencing?"

Sapra's technique to do this involves using sugars, such as glucose, labeled with carbon isotopes. When the organism utilizes that sugar, it breaks it down into simpler smaller carbon sugars. Based on where those isotopes end up, the researchers can determine possible pathways that led from the starting sugar to the end product. "That gives us a method of rapidly deducing the operational pathways and how the pathways and how the flux through those pathways is distributed, which is the more important part," Sapra said. "The organism may produce ethanol, but if the flux-or the carbon that goes through that pathway-is in a very small amount, then you're never going to have high ethanol production. So, what you have to do is increase the flux through those pathways."

"The major advantage we see with this method is the turnaround time," Sapra said. There is a lot of attention being paid to biofuels right now, but Sapra said the amount of research and development that goes into developing those fuels is often overlooked. "The idea is if you are doing bioprospecting or looking for a host, you need sort of a quick and dirty answer before you spend a lot of time and effort into analysis [of that microbe]," Sapra continued. "The idea is to figure out on a pretty fast time scale whether a newly discovered organism has the necessary metabolic pathways to produce a particular end product that may be used as a starting point for fuel production. It is an analysis technique, something that can give us an answer about the feasibility of the organism as a fuel production host." In other words, this analytical method can help prevent losing time and money studying a microbe that won't be feasible for fuel production.

JBEI, which is funded by the U.S. DOE through Genomics:GTL (formerly Genomes to Life), a program in the Office of Biological and Environmental Research in the Office of Science, is tasked with finding methods to sustainably convert cellulosic biomass to fuels and reduce greenhouse gases.

Source: Ethanol Producer Magazine