New Scientist: A chemical chimera may one day help break down stubborn plant matter into biofuel. The feat involves mixing enzymes from two types of plant-munching bacteria that would never have met in nature.
Biofuel producers use the sugars in crops such as corn to create alternative fuel that is more climate friendly than gas or coal. But biofuels that use cheap, widespread plant matter such as leaves and grasses would be even more attractive than food crops. Trouble is, those parts of plants are high in cellulose, a sturdy structural compound that is hard to break down.
Microbes living in oxygen-rich environments use enzymes floating free inside their cells to digest such plant matter. Bacteria that live in places with low or no oxygen – in a cow’s stomach, say – instead use complex scaffolds of enzymes known as cellulosomes. Free enzymes are fast-acting, while cellulosomes are slower but highly efficient.
Yonathan Arfi and Ed Bayer at the Weizmann Institute of Science in Rehovot, Israel, designed a chemical reaction that fused a free-floating enzyme particularly effective against cellulose onto a cellulosome. The resulting hybrid is quick and efficient at turning cellulose into useful sugars.
Until now, the processes that have evolved over billions of years in anaerobic bacteria have never had a chance to work with those that evolved separately in aerobic bacteria. “Two enzymes that would never make sense in nature have this functional synergy,” says Brian Fox, a biochemist at the University of Wisconsin-Madison.
Bayer says the advance is not yet enough to make better biofuels, but it boosts our understanding of the agents involved. “This was a lot of fun for us. It’s like playing with Lego, except in a test tube,” he says.
Leaves and straw
Vincent Eijsink at the Norwegian University of Life Sciences in Ås says research like this could help make possible a new generation of efficient biofuels that don’t rely on food crops.
Using existing technologies, the first commercial-scale cellulosic biofuel plants are just now starting to come online. A plant operated by Novozymes in Crescentino, Italy, is already producing 50 million litres of ethanol every year from rice straw.
Du Pont is currently building a 113-million-litre plant to digest the leaves and stalks of maize in Nevada, Iowa, and Spanish company Abengoa is about to start operating a similarly sized plant in Hugoton, Kansas.
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