Making better biofuel-producing bacteria

Scientists have long been trying to bioengineer bacteria to produce fuel that can be used instead of traditional fossil fuels. But one problem they have faced is that the fuel is toxic to the bacteria, and once they make it, it slows their growth so only limited amounts of fuel can be generated this way. Now, an international team of researchers has gone some way to eliminating this problem, by creating bacteria with a higher tolerance to the fuel they produce.

The compound isopenetol (which works like gasoline) can be produced by genetically modified E. coli bacteria, but solvent-like compounds in the biofuel slow the growth of bacteria, meaning this method produces only a little fuel. In this latest research, scientists attempted to raise the tolerance of the bacteria to the solvent. They achieved this by looking at which genes are expressed (turned on) by the bacteria when they are exposed to the solvent, as these genes probably have some protective effect. The researchers then over-expressed these genes (turned them on a lot) in other bacteria. From this, they found two genes that could sustain bacterial growth in the solvent, MetR and MdlB. Over-expressing MetR improved production of the fuel by 55%, with MdlB improving it by 12%, though by increasing the level of protein produced by this gene in cells, this reached 60%.

The MdlB gene is considered more promising by researchers, because it produces a transporter protein, and therefore could help transport the solvent outside the cell. If enough fuel accumulates outside of the bacterial cell, it could separate from the watery broth the bacteria live in and sit on the surface, making it easier to siphon off and less likely to affect the bacteria.

Developing these biofuels from bacteria is appealing because they can be easily mixed with normal petrol so work with our current infrastructure. This is in contrast to to other technologies such as electric cars which require new infrastructure like charging stations to be built. If the tolerance of the biofuel-producing bacteria can be increased, we could quickly reduce our reliance on fossil fuel.

Reference

Foo, J., Jensen, H., Dahl, R., George, K., Keasling, J., Lee, T., Leong, S., & Mukhopadhyay, A. (2014) Improving Microbial Biogasoline Production in Escherichia coli Using Tolerance Engineering. mBio, 5(6). DOI: 10.1128/mBio.01932-14

Image credit: Wikicommons

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