Two Stanford researchers have found a way to use E. coli to produce biodiesel fuel. Xingye Yu, a Ph.D. candidate, and Tiangang Liu, a post-doctoral student, recently used E. coli to model fatty acid synthesis in vitro, yielding fatty acid derivatives that can be converted into biodiesel.
“These findings reinforce our earlier conclusion that, among these metabolites, only the intracellular concentration of malonyl-CoA is likely to be an attractive target for further engineering, if the goal is to improve fatty acid yield and/or productivity,” Yu wrote in an email to The Daily.
There is a scene in “Back to the Future II” when Doc Brown reaches into Marty’s garbage can, pulls out a few banana peels and uses them to power his automobile-based time machine. This type of technology is not science fiction anymore.
The team discovered that E. coli’s cellular machinery is useable at points before and after a particular section of the assembly line. In particular, it could harness a particular type of plant biomass–called lignocellulosic raw materials–at an earlier point in the reaction to increase cost-effectiveness and create a better biodiesel alternative.
“The good news is that the engine that makes fatty acids in E. coli is incredibly powerful,” said Chaitan Khosla, a professor of chemistry and biochemistry, in an interview with the Stanford Report. “The bad news is this engine is subject to some very tight controls by the cell.”
The fatty acids that the E. coli creates cannot be directly pumped into a car’s gas tank, however they are a precursor to biodiesel fuel.
Enzymatic reactions are like assembly lines, and thus, Yu says speeding up production at a particular point can impact the entire reaction rate.
“Additional research efforts are also warranted upstream and downstream of these biofuel synthesizing steps,” Yu said.
Production cost, efficiency and sustainability are the main concerns when producing biodiesel. Yu and her lab’s research point to E. coli as a promising factory of biodiesel production. They note that E. coli’s natural rate of conversion is not commercially viable. However, the researchers hope to improve this by changing its internal machinery and boosting its conversion capabilities.
According to Yu, researchers must also consider the product yield from a specific amount of reactant. She noted that researchers should seek to reach the theoretical maximal yield of 30 percent. Reaching this yield will make E. coli a more favored biodiesel alternative.
“Currently only about 20 percent of this value is achieved,” Yu said, later adding, “We aim to increase the yield as high as possible while keeping the process economically sound.”
This process is also more sustainable than biodiesel production due to a range of factors.
“There will be no competition with food production, no seasonal/geographical variation of raw material supplies and no dependence on petrochemicals,” Yu said. “E. coli grows fast and is quite amenable to genetic manipulation.”
Yu and Liu’s biofuel research is currently funded by LS9, Inc., a San Francisco-based biotech startup that seeks to use synthetic materials to provide sustainable products.