C5 is the new C6

December 15, 2015 |

C5newC6Goodbye glucose, hello xylose. The X-Factor in the advanced bioeconomy might just be a sugar that starts with an X.

You’ve long noticed that water gathers in beads — on a leaf in the morning, for example, or dripping from a faucet. That’s surface tension, which is to say that the water is more attracted to itself than to the surface it is encountering, so it essentially rolls up into a ball. Not entirely unlike an uncooperative child.

Every once in a while, you see something weird like a paper clip floating on water. That’s the same phenomenon. The object can’t be wetted and the forces exerted by surface tension prevent the metal from sinking.

In the world we live in, we sometimes need to increase wettability or decrease surface tension. Consider laundry. Just like water on a waxy leaf, water in your washing machine won’t get the grease out because water and grease repel each other.

That’s where a surfactant comes in, because it’s a molecule with one end that is attracted to water, and one to oils and greases. The surfactant attaches itself to the dirt or grease, then the water molecule attaches to the surfactant, and together they pull the dirt out of clothing. That’s how soap and detergents work.

New Paths for the C5s

It’s just one of the many products that, these days, can be made from a C5 molecule such as xylose or arabinose. When we think about C5s — that are liberated by new technologies from the cellulosic material they reside in, such as woods or plants — we generally think about them as a sort of “me-too” cousin of traditional C6 sugars like glucose (cane sugar) or dextrose (corn sugar), suitable for fermentation into ethanol. More on the scientific basis for making surfactants from C5s, here.

But Digesterati such as David Dodds (of Dodds & Associates) and Ron Cascone (of Nexant), also seen frequently on  the ABLC stage and on BioChannel.TV, suggest that we are overlooking the usefulness of C5s.

“As the biorefinery concept becomes real,” says Dodds, “the stream of 5-carbon sugars (from hemi-cellulose) is going to be a new 5-carbon chemical feedstock.  It has a greater advantage when seen in this perspective than as “fermentable sugar”.  Five-carbons is a bit of an orphan at the moment, but it is nicely inside the “4 to 6 carbon deficit” and is odd-numbered.  The only identifiable 5C bio-based chemical I can easily bring to mind is levulinic acid, and it is struggling to find a decent market.  Faced with a reasonably clean and abundant 5C feedstock, I predict the chemical industry will try to find use it.”

Cascone agrees. “C5 sugar (grey) is the new C6 sugar (black).  Amyris is the 5-carbon poster child – farnasene /farnasane /squalene, etc. (5×3), d-limonene (5×2), and isoprene (5), but also DuPont-Genencor/Goodyear, and other isoprene developers.  Amyris / JBEI was originally funded by the Bill & Melinda Gates Foundation to develop (and did) fermentation routes to the malaria drug, artemisinin  (C15H22O5). It’s a mess of a molecule, but definitely in the C5 family. However, alas, they feed on glucose, fructose, and the like, and I believe the yield of all the isoprene fermentation technologies is still very low.”

“Amyris started on Jay Keasling’s terpene pathway work,” Dodds noted, “and the acquisition of Allylix by Evolva in Switzerland means that Evolva now has a major IP position in terpenes; they are the largest group of natural products.

But Dodds steers the conversation away from biological conversion quickly.

“I’m not just thinking biologicially (gasp!) when I ask what C5 chemicals are out there; the terpene pathway is very carbon-inefficient.  I was wondering what would come out of a reformer or other by-product stream in the current petro-based chemical processes.  A starting material to glycols seems fair – one could theoretically get glycerin and ethylene glycol.”

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Moving from the theoretical to the real-world: Sweetwater Energy

One of the most amazing corporate journeys we’ve seen in recent years parallels this discussion — that’s the evolution of Sweetwater Energy in the face of the cellulosic biofuels slowdown. Once, Sweetwater was going to content itself as a supplier of cellulosic sugars for all those cellulosic biorefineries that were imminently expected. Not long after the company’s formation came a string of MOUs with prominent firms that were developing along those lines.

But then there was the screeching halt in cellulosic biorefinery deployment, which the industry attributes to the Obama Administration’s stewardship over the Renewable Fuel Standard. It took, for example, the Administration until two weeks ago to finalize mandated volumes for 2014. And volumes were way below Congressional targets for 2016 and 2016 for reasons that no one can quite yet find in the law.

As market signals go, it’s about as successful with potential investors as the prospect of a tax audit.

Sweetwater, no surprise, has repositioned — and what we except to see is that the company will be producing some product on its own at its first commercial biorefinery — and that primarily means higher-value chemicals made from sugars, and naturally that brings us to C5s.

The Sweetwater,Taurus and Lallemand hook-up

Though official word from Sweetwater is not yet forthcoming — they’ve grown shy of “getting ahead of the story” since the death of all those MOUs — we had a strong confirmation that this is the new direction when Taurus Energy , with Lallemand Biofuels and Distilled Spirits, signed an LOI with Sweetwater Energy for the supply of XyloFerm to Sweetwater.

No order values ​​or time frames are specified and it is still too early to say when a deal might be finalized, but what’s important is that XyloFerm is a yeast strain for producing ethanol from C6 and xylose streams. XyloFerm’s magic? Offering minimal byproduct formation with a high tolerance for inhibitors common with cellulosic substrates.

Taurus and Sweetwater themselves hooked-up earlier this year with an agreement for collaboration with respect to the development, marketing, sale and distribution of Taurus’ Gen 2 platform on the U.S. market.

The Sweetwater rationale

For now, Taurus has not yet completed all the steps for XyloFerm to be used as an ingredient in animal feed. If XyloFerm is approved as a feed component the strain may also be used by ethanol producers who sell their fermentation residues on for use as feed. For now, cellulosic sugars that do not produce an animal feed additional product — well, they’re ideal.

What’s next?

Dodds mentions ethylene glycol (MEG) and glycerin. MEG, that’s a key ingredient in Coca-Cola’s Plant Bottle, making up 30% of the clear bottle plastic. There’s a $27B annual market there.

The search for low-cost, bio-based MEG led Liquid Light and Coca Cola to sign a technology development agreement to accelerate the development of MEG from carbon dioxide. Using Liquid Light technology, an ethanol production facility could make bio-MEG from the CO2 byproduct that results from converting plant material into ethanol. The technology has the potential to reduce both the environmental footprint and the cost of producing MEG.

As Liquid Light makes clear, current Bio-PET is expensive and it’s a multi-step procedure. So, there’s reason to focus on Liquid Light’s process, which makes MEG from oxalic acid, in turn made from CO2.

But there’s a C5 pathway as well. And with a $27B market to chase, there’s going to be more than one happy landing if the technology and economics work out.

Which is good enough reason to keep an eye on those C5s — not only as “me-too” fermentable sugar for ethanol and fuels, but as a platform for all kinds of interesting chemistry.

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