Pooping pandas may make better biofuels

Gut microbes break down bamboo efficiently, inspiring new approaches to process raw plant materials for fuel

Two giant pandas in the Memphis Zoo have dropped researchers a gift. Studies of the pandas’ poop show that their gut microbes break down bamboo efficiently — a trick that humans could co-opt to turn woody plant material into alternative energy sources.

RAW FUEL Bamboo passes quickly through pandas’ gastrointestinal tracts thanks to powerful microbes that digest it, scientists have found. The trick could be useful someday for making biofuels. A. Witze

“We’re taking refuse — panda poop and the microbes that live there — and trying to break down another form of refuse,” says Ashli Brown, a biochemist at Mississippi State University. Brown described her team’s results on August 29 at a meeting in Denver of the American Chemical Society.

Pandas eat bamboo almost exclusively, but don’t have a multichambered stomach like cows to help digest all those plants. It’s basically in one end and out the other, and “anything residing there to break down woody material has to be very efficient,” says Candace Williams, a graduate student on Brown’s team.

Williams began by studying how pandas extract nutrition from bamboo, and says it was natural to think of other things to do with the feces she got from YaYa and LeLe at the zoo. So for 14 months she counted members of eight common bacterial groups, such as Clostridium, within the poop. Williams discovered 12 species of waste-digesting bacteria, including at least one never before seen in pandas.

The scientists are now trying to extract the enzymes these bacteria use to chew up plants. Preliminary work suggests the bacteria are at least as efficient at digestion as similar ones found in the guts of wood-chomping termites, Brown says.

Once isolated, the enzymes could be produced in the lab and possibly used to speed up the complicated, expensive process of turning the tough, fibrous plant material known as cellulose into biofuel.

“The goal will be to establish bioreactors in which cellulose will be converted into hydrogen and/or methane,” says Jose Rodriguez, a chemist at Mississippi State who is not involved with the research. But getting the microbes to stay alive in such reactors can be a challenge, he warns.

For now, Brown’s team is moving ahead with the poop studies. Because all the bamboo comes out looking like hay, panda poop “is probably the most pleasant fecal material to work with,” Brown says. “Candace and I have worked with other poo, and we can assure you it has a fairly pleasant smell associated with it.”

Alexandra Witze is a contributing correspondent for Science News. Based in Boulder, Colo., Witze specializes in earth, planetary and astronomical sciences.

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