On the Enzyme Hunt

September 7, 2011 | Leave a Comment

Ashli Brown, Ph.D. and colleagues, including graduate student Candace Williams at Mississippi State University have taken the hunt for enzymes to break out the sugars from the super-tough plant material known as lignocellulose in switch grass, corn stalks and wood chips to the Giant Panda.

The panda digestive tract contains bacteria with potent effects in breaking down plant material in the way needed to tap biomass as a major new source of “biofuels” produced not from corn and other food sources, but from grass, wood chips and crop wastes.

Brown and the colleagues reported their research work at the 242nd National Meeting & Exposition of the American Chemical Society in Denver.

Brown says in the press release, “Who would have guessed that ‘panda poop’ might help solve one of the major hurdles to producing biofuels, which is optimizing the breakdown of the raw plant materials used to make the fuels. We hope our research will help expand the use of biofuels in the future and help cut dependency on foreign oil. We also hope it will reinforce the importance of wildlife conservation.”

Scientists have long known that giant pandas — like termites and cattle — have bacteria in their digestive systems to break down the cellulose in plants into nutrients. Bamboo constitutes about 99 percent of the giant panda’s diet in the wild. An adult may eat 20-40 pounds of bamboo daily — leaves stems, shoots and all. Until the energy crunch fostered interest in biofuels, however, scientists never thought to parse out exactly what microbes in the giant panda gastrointestinal system were involved in digestion.

Brown and her team collected and analyzed the fresh feces of a pair of male and female pandas at the Memphis Zoo for over a year. They identified several types of digestive bacteria in the panda feces, including some that are similar to those found in termites, which are renowned for their ability to digest wood.

“Our studies suggest that bacteria species in the panda intestine may be more efficient at breaking down plant materials than termite bacteria and may do so in a way that is better for biofuel manufacturing purposes,” said Brown.

Based on other studies, Brown estimated that under certain conditions these panda gut bacteria can convert about 95 percent of plant biomass into simple sugars. The bacteria contain enzymes — highly active substances that speed up chemical reactions — so powerful that they can eliminate the need for high heat, harsh acids and high pressures currently used in biofuel production processes, she said. Those processes also tend to be time- and energy-intensive, as well as expensive. Panda bacteria could therefore provide a faster, cleaner and less costly way to make biofuels.

Brown is currently trying to identify every intestinal bacterium in the giant panda in order to isolate the most powerful digestive enzymes for biofuel production and other purposes. She noted that scientists could use well-established genetic engineering technology to put the genes that produce those enzymes into yeasts. The yeasts then would produce the enzymes and could be grown on a commercial scale to provide large amounts of enzymes for a biofuel industry.

Panda Chows on Bamboo. Click image for the largest view.

In the press release Brown notes the value of preserving biodiversity, “The discovery also teaches a lesson about the importance of biodiversity and preserving endangered animals,” Brown said, noting that less than 2,500 giant pandas remain in the wild and about 200 are in captivity. “Animals and plants are a major source of medicines and other products that people depend on. When we lose them to extinction, we may lose potential sources of these products.”

One hopes Ms. Brown is on the right track, the termite work hasn’t gotten anywhere that’s been announced yet, and years have been invested..  On a comparative basis though, wood as see in the termite diet and nearly pure bamboo in the panda’s are both much more structurally sound than the easy things like crop wastes.

There’s a lot of biomatter out there for fuel production and getting humanity current with the planetary carbon cycle is a real good idea.  If Brown can get to 95% using most agricultural and forestry wastes cellulosic ethanol could get a boost.


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