A new suit for the Man of Steel?

| April 9, 2013

super-materialsA long-known, biobased, microscopic “super-material” may become highly affordable and scalable.

Perfect for both Superman’s needs and Clark Kent’s budget.

Me: Let’s play 20 Questions, the Biobased Game.
You: OK, I’ll start. Think of a biobased material.
Me: Got one.

You. Is it stronger than steel?
Me: Yep.

You: Is it stiffer than Kevlar?
Me: Correct.

You: Is it lightweight and compact?
Me: Right again.

You: And we expect to be able to mass produce?
Me: Yep.
You: I got it. It’s spider silk.

Well, there you’d be right and wrong. There is a lot of interesting work being done on spider silk — but we’re a ways away from a commercial process whereby we can make it at scale.

Imagine something with even a wider set of uses, but all those characteristics. In fact, we could even use it as a food, or as a basis for energy. And, we’re getting quite close to a process to make it abundantly. Using primarily water and CO2.

By now, you might have guessed that we are referring to the strange world of nanocellulose.

As was reported this week out of an American Chemical Society symposium:

“Most cellulose consists of wood fibers and cell wall remains. Very few living organisms can actually synthesize and secrete cellulose in its native nanostructure form of microfibrils. At this level, nanometer-scale fibrils are very hydrophilic and look like jelly. A nanometer is one-millionth the thickness of a U.S. dime. Nevertheless, cellulose shares the unique properties of other nanometer-sized materials — properties much different from large quantities of the same material. Nanocellulose-based materials have great strength, light weight and other advantages has fostered interest in using it in everything from lightweight armor and ballistic glass to wound dressings and scaffolds for growing replacement organs for transplantation.”

Yes, it’s the nanometer-sized version of cellulose, the most abundant organic polymer on Earth. It was Louis Pasteur who first discovered that acetobacters — that is, bacteria responsible for making vinegar (that you might find, for example, making your wine go sour or turning your milk into yogurt) were capable of making “a sort of moist skin, swollen, gelatinous and slippery”.

That’s bacterial nanocellulose — and there’s a cottage industry involved in its manufacture.

But the very interesting news coming out of the aforementioned ACS Symposium on Nanocellulose in New Orleans this week, its that a team of researchers from the University of Texas led by Malcolm Brown have enhanced the ability of cyanobacteria — or blue-green algae — to make nanocullose.

Why significant? Because those blue-green algae can utilize CO2 in the process. Thereby sequestering our problem child gas, while making what has been dubbed the latest “wonder material” in the process.

Yep, that’s right. Turning the greenhouse gas problem into a feedstock for making fabrics that Superman might not mind having a bolt of, and food additives that even a nutritionist would warmly embrace.

Brown recalled that in 2001, a discovery by David Nobles, Ph.D., a member of the research team at the University of Texas at Austin, refocused their research on nanocellulose, but with a different microbe. Nobles established that several kinds of blue-green algae, which are mainly photosynthetic bacteria much like the vinegar-making bacteria in basic structure; however, these blue-green algae, or cyanobacteria, as they are called, can produce nanocellulose.

One of the largest problems with cyanobacterial nanocellulose is that it is not made in abundant amounts in nature. If it could be scaled up, Brown describes this as “one of the most important discoveries in plant biology.”

Since the 1970s, Brown and colleagues began focusing on Acetobacter xylinum (A. xylinum), a bacterium that secretes nanocellulose directly into the culture medium, and using it as an ideal model for future research. Other members of the Acetobacter family find commercial uses in producing vinegar and other products. In the 1980s and 1990s, Brown’s team sequenced the first nanocellulose genes from A. xylinum.

They also pinpointed the genes involved in polymerizing nanocellulose (linking its molecules together into long chains) and in crystallizing (giving nanocellulose the final touches needed for it to remain stable and functional).

But Brown also recognized drawbacks in using A. xylinum or other bacteria engineered with those genes to make commercial amounts of nanocellulose. Bacteria, for instance, would need a high-purity broth of food and other nutrients to grow in the huge industrial fermentation tanks that make everything from vinegar and yogurt to insulin and other medicines.

Those drawbacks shifted their focus on engineering the A. xylinum nanocellulose genes into Nobles’ blue-green algae. Brown explained that algae have multiple advantages for producing nanocellulose.

Cyanobacteria, for instance, make their own nutrients from sunlight and water, and remove carbon dioxide from the atmosphere while doing so. Cyanobacteria also have the potential to release nanocellulose into their surroundings, much like A. xylinum, making it easier to harvest.

In his report at the ACS meeting, Brown described how his team already has genetically engineered the cyanobacteria to produce one form of nanocellulose, the long-chain, or polymer, form of the material. And they are moving ahead with the next step, engineering the cyanobacteria to synthesize a more complete form of nanocellulose, one that is a polymer with a crystalline architecture. He also said that operations are being scaled up, with research moving from laboratory-sized tests to larger outdoor facilities.

The bottom line

Early days for the technology – still in the lab, not in the field. And much would depend on cost-effective means of growing and maintaining the said nanocellulose-secreting cyanobacteria. But it certainly is a hot area of research in the biobased revolution in the way it fastens a robust problem such as rising CO2 levels to a production process for making a multi-faceted material that is in great demand and will be more so as costs come down.

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