Published on January 16th, 2013 | by Tina Casey0
Tiny But Tough Nanobowls Offer a Pathway to Low Cost Biofuels
Scientists at Argonne National Laboratory have figured out a way to synthesize nanoscale, bowl-shaped “enzymes” that mimic the way real enzymes selectively interact with other molecules, but that are far more durable and hardy than their natural counterparts. The breakthrough will enable researchers to develop efficient, low cost catalysts for making a variety of products including advanced biofuels.
Making Nanoscale Bowls, Atom by Atom
According to Argonne writer Jared Sagoff, the synthetic nanobowls use the same “lock and key” mechanism that generally characterizes natural enzymes.
In both cases, the enzyme can be described as a lock, that will only open in response to a molecule of exactly the right shape and size.
The problem with natural enzymes, in terms of biofuel production, is that they operate most efficiently under natural conditions. In other words, they generally cannot tolerate the extremes of temperature and pressure that characterize advanced biofuel production.
In addition to developing more durable enzymes, a related challenge is to lower the cost of enzymes as a proportion of the cost of biofuel.
To build the synthetic enzyme, the researchers used a large bowl-shaped organic molecule called a calixarene as a template. They put the calixarene on a surface made of titanium dioxide (a photocatalyst that can “eat” smog and perform other sustainability-related functions), and used atomic layer deposition to build up walls of aluminum oxide around the template.
Once the walls reach the desired height, the calixarene is burned away, leaving the bowl-shaped inorganic “enzyme.”
By manipulating the size and depth of the bowl, researchers can custom-build the synthetic enzyme so that only a molecule of exactly the right type will fit inside. Basically, the nanobowls perform the function of a sieve, which sorts out undesired molecules that would spark uncontrolled reactions.
The Quest for the Perfect Biofuel Enzyme
Durable, precision-tailored catalysts would go a long way toward enabling the biofuel industry to achieve price parity with fossil fuels, but the Argonne research has a way to go before its application to biofuel production can be demonstrated conclusively.
In the meantime, researchers have also begun to identify extremely hardy enzymes in nature that could be further modified to withstand the biofuel production process.
For example, a team of researchers at another Department of Energy project, the Joint Genome Institute, has identified a pair of heat-tolerant fungi called Thielavia terrrestris and Myceliophthora thermophila. Their enzymes can tolerate temperatures up to 75 centigrade, compared to a limit of 35 degrees for the typical enzyme.
Researchers are also looking at a class of bacteria called extremophiles, which can be found in unusually harsh environments such as undersea thermal vents.
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