Doing it in the Dark: Fuel from thin air, and beyond light

May 23, 2013 |

Bossie-7942-imageBeyond fossil fuels, beyond light itself.

And now, the direct production of drop-in biofuel blendstocks. All available from a microbial “cow”.

This week in California, a research team from Shota Atsumi’s lab at the University of California, Davis have reported that they engineered Synechococcus elongatus PCC 7942, a strain of photosynthetic cyanobacteria, to grow without the need for light.

OK, who’s S. elongatus 7942?


Those who work in the dark arts of microbial engineering know that Synechococcus elongatus PCC 7942 was the first cyanobacteria that could be reliably transformed by altering its DNA — and it’s been a model cyanobacteria ever since.

Here in Digestville, we call her Bossie.

She’s one of a new generation of organisms that researchers, and most recently, companies have been developing (and scaling up production) that can be “milked” as a producer of biofuels and other valuable targets.

The biomass dependency

The tradition of biofuels has been that the production has required crushing, gasification, or some other form of destruction of biomass. Most famously, the crushing of cane, soybeans or rapeseed — or the grinding of corn.

From that basic substrate have traditional biofuels been made.

But let’s think about milk and meat, for instance.

In meat production, you use the animal directly and slaughter it in the process. In milking, you use the animal’s byproduct, and the animal lives. Is it more efficient to make biomass, then kill it, then transform it into something useful, or simply to make it into something useful from the start?

Beyond batch production, the super critters

When cellulosic and advanced biofuels came along — there were a new class of microorganisms that could do far more interesting things that the workhorses of wines and biofuels, saccharomyces cerevisiae yeasts, that ferment batches of sugars into ethanol.

The new microorganisms were supercritters — they could make targeted byproducts – fuels, chemicals, triglyceride oils and more – in long continuous runs, where products could be separated off – no loss of the microorganism itself.

There were the class of microorganisms that make isobuntaol or n-butanol, developed by Gevo, Butamax, Green Biologics and Cobalt. The consolidated bioprocessing bugs of Mascoma and Qteros. The sugar-transforming microcritters developed by Solazyme, Amyris and LS9. To name a few.

But that generation, as a whole, used an underlying biomass that still had to be crushed – corn, cane or cellulosic biomass. (One exception, LanzaTech’s remarkable critter, can make biofuels from carbon monoxide waste gases.)

Beyond biomass, the “fuel from thin air” microvarmints

Then, along comes a whole generation of companies have sprung up that use the miking method — and can use sunlight, water and CO2 directly to make a targeted fuel.

Algenol, for example – with its genetically reengineered algae that produce ethanol as a byproduct. Joule, with its modified cyanobacteria that makes biofuels and chemicals “from thin air” (CO2, brackish water and sunlight). There’s Proterro, which uses some of the same ideas — in this case with an aim of producing a renewable sugar.

Beyond light and the limits of photosynthesis

One limitation? The problem of light. Imposing some limitations on the production of targeted products to the daylight hours — more importantly, restricting the locations to places that had good solar insolation. Which don’t always line-up perfectly well with the availability of water, or CO2, or low-cost-land. Plus, you had the problem of photosynthetic efficiency itself — which never gets above 10 percent (a fraction of the efficiency of solar PV).

That was one of the reasons why our March report on “Biofuels from a raging fireball? No fossil energy, no light, no biomass, no sugars. No kidding” drew so much attention.

There, we highlighted work on “Liquid Fuel from Heat-Loving Microorganisms. A team from the University of Georgia and North Carolina State team, led by Michael Adams, had engineered Pyrococcus furiosus to make 3-hydroxypropionic acid using hydrogen gas, and CO2.

We wrote at the time: “Since 3-hydroxypropionic acid rarely comes up at cocktail parties — we’ll describe it as one of the DOE’s top 12 value added building-block chemicals from its 2004 survey…More importantly, if you can make that today — you can make fuels down the line.”

Making isobutanol

“Where the hydrogen coming from?” asked a number of astute readers at the time. And for sure, it was coming not from water, but from hydrogen gas. Which is generally made from fossil fuels (though it can be made renewably).

So, how is this latest news from UCD an advance of the storyline? In two ways — one, we haven’t seen the requirement for hydrogen gas: water seems to be able to provide the hydrogen. Secondly, we note that the targeted products that Bossie can make include, to date, isobutyraldehyde and isobutanol.

The former, a precursor for the synthesis of other chemicals, and the latter is the well-known gasoline substitute that companies such as Gevo, Butamax and Green Biologics are chasing. Isobutanol can be directly blended as a gasoline feedstock, today.

There appear to be some limitations to the organism. In this case, it appears that it has been converted from a light-lover to a sugar-lover, thereby conferring a dependency on biomass and putting it into the Solayzme, Amyris, LS9, Gevo class of organisms that use an underlying sugar. In this way, it differs from the electrofuel class of organisms that can derive their energy without the use of biomass. But the use of CO2 gives Bossie a special place even in this exalted pack.

The breakthrough remains at lab-scale for now.

The breakthrough remains at lab-scale for now.

Where is the team in scale-up?

It’s at lab-scale for now – a long way from the market, unless you have a really, really tiny car that needs, say, a couple of grams of fuel per year.

The Digest’s Take: Threats and Opportunities

If Bossie were a fault-line, she’s be like the San Andreas – possessing a definitively and massively power to transform landscapes, but the timeline is uncertain.

The opportunity. For those who like drop-in fuels, and post-biomass microvarmints, this one’s a beauty, in prospect. We may well wish to see how some of the same traits could be transferred from a model organism to a production organism — one that is able to tolerate scaled-up production conditions, before getting too excited, But you get the idea.

A Heifer worth watching

We like Bossie. Bacteria, yeast, algae — all have been interesting platform micro-organisms. To date, cyanobacteria has been used very sparingly (Joule is using it, with a photosynthetic organism). Cyano has some very attractive properties, one of which is the relative ease of engineering within its small genomic footprint — and it can be a highly productive organism.

It may be a long time before Synechococcus elongatus PCC 7942 replaces Ayrshire, Guernsey, Jersey, or Holstein in the popular vocabulary. But here, at microscale, is a heifer worth watching.

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