Mar 21 2011

Fuel From Bacteria

We are used to thinking of bacteria as germs – something to be shunned. In fact, the vast majority of bacteria species are indifferent to humans – they are neither helpful nor harmful. A small minority of species are pathogenic, capable of infecting humans and causing harm. And a small number of species live symbiotically with humans. We all carry an ecosystem of about 100 bacteria species in and on us.

With genetic engineering technology we have also created a fourth category of bacteria – those that can be used as microscopic factories. For years we have been using bacteria to cheaply manufacture drugs and other compounds. Just insert the gene for human insulin in the right place, and the little buggers start cranking it out.

Researchers are exploring the use of genetically engineered bacteria for other uses as well. For example, bacteria have been shown to secrete nanotubes, and can potentially be used for microelectronics.

But the potential application that seems to be getting the most press attention is making biofuels from bacteria. Bacteria can function to digest a biofuel crop, like switch grass, typically breaking down the cellulose so that it can be processed into ethanol. But a potentially superior approach would be to have bacteria produce fuel directly. Because the direct method avoids potentially expensive steps, it is likely to be more cost-effective, which is critical for the adoption of any alternative fuel.

There are frequent news items claiming breakthroughs in this technology, but two I want to mention specifically. Here’s the first.

The findings, reported online in the journal 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.

They achieved this with a modified version of the common bacterium, E. coli.

A second team announced a few weeks ago that they modified a cyanobacterium to produce diesel fuel or ethanol.

These are both exciting breakthroughs – bacteria essentially can thrive on waste and sunshine and produce biofuel. They fix carbon from the atmosphere, which then gets released upon burning, so such biofuels would be carbon neutral (the same is not true of some crop-based biofuels where the crops are fertilized with petrochemical-based fertilizer).

I have actually been reading about claimed breakthroughs with bacteria to fuel technology for a few years. This is one of those future technology news items that is hard to know if it will pan out, and how soon. Is this a hand-held computer or jetpack? It seems that there are non-trivial technical hurdles to overcome, mostly involved with scaling up the production. It’s one thing to make diesel fuel in some small test containers, another to run a massive factory generating millions of gallons. If the process can’t scale up, we won’t ever be pumping it into our cars.

What is clear is that engineered bacteria are already a proven technology, and I think it’s probable that they will be increasingly used in the future. Beyond being microfactories, researchers are exploring the use of engineered bacteria to augment the bacterial flora of our bodies, with potential health benefits.

But predicting any particular application is difficult. I think the chances are good for biofuel from bacteria, and I certainly hope this technology pans out. But it remains to be seen.

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