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Biofuels Researcher Goes ‘Rumen Fishing’ Inside The Cow Stomach For Answers

Urbana – What can a leading University of Illinois microbiologist doing research on biofuels learn from a cow?

Plenty if that scientist is Professor Bryan A. White.

“The bottom line is I view the ruminant as a source of enzymes to break down plant cell walls,” White said during a recent interview. “The ruminant is very, very efficient at breaking down all kinds of plant cell walls. If you look at the stomachs or rumen of a cow (which actually has a four-chambered stomach), it is like suddenly having access to a tool box with every available widget to break down all of the various components of plant cell walls with various kinds of architectures and made of a number of different substances.”

Today, researchers at the U of I are studying how to use biomass from widely available plants—ranging from miscanthus to corn stover ( the plant leftovers after the corn ear is harvested) to alfalfa and other traditionally grown field crops—to produce ethanol, butanol and other bio-based fuels. While some scientists are concerned with the synthesis of such fuels, White is focusing on breaking down plant cell walls into basic building blocks that can then be used to build new substances.

White, who earned a Ph.D. in microbiology from the Medical College of Virginia at the Virginia Commonwealth University and a bachelor’s degree in biology from Virginia Wesleyan College, is a tenured professor of Animal Sciences in the College of Agricultural, Consumer and Environmental Sciences at the U of I and heads up the graduate program in the Department of Animal Sciences. The proper name for his work is “Enzymatic Hydrolysis of Forage Cell Walls.” Said more simply, his research focuses on using enzymes to break down the cell walls of various plants. The enzymes he currently is using are those he has found from microbes in the cow rumen.

“In doing this work, we have to concern ourselves with composition—what the cell walls we’re trying to break down are made of—and architecture—how the walls are put together or assembled.

“The ruminant model is ideal for us to use and learn from because ruminants ingest this material and deal with it automatically,” he said. A ruminant is a mammal that digests its food in two steps, first by eating the raw material and regurgitating a semi-digested form known as cud from within its first stomach, known as the reticulum. The process of again chewing the cud to break down the plant matter and stimulate digestion is called ruminating. Ruminants include cattle, goats, sheep, camels, bison, deer and antelope. White and others at the U of I are working with cattle because their rumination process works quite well to digest the grasses and other Midwest feedstocks that scientists are interested in growing for biofuel production.

White says microbiologists can now think of the microorganisms in the ruminant stomach as a type of organ—“as if it were a single beast of some sort. That’s one way to define Metagenomics. Instead of looking at individual microbes, we acknowledge that we are studying a very complex entity. ‘Meta’ is Greek for ‘All’ and genomics is the study of genetic material recovered directly from environmental samples.”

White suggests it is helpful to think of the microorganisms in a ruminant stomach as a factory that is composed of generalist workers, which are “Jacks-of-all-trades” and can do a lot of things but none of them very well, and specialists, which are fewer in number and do only one task but do it very well.

“The so-called specialists that we are looking for are the ones that break down the ligno-cellulosic walls of plant matter. Those are the ones we are trying to tease out and use in the laboratory,” he says.

One of the organisms found in cow rumens that White currently is focusing on is a bacterium called Ruminococcus flavefaciens. It was originally isolated at the U of I in 1961 by well-known microbiologist Marvin Bryant and produces more than 115 different enzymes that break down plant cell walls.

Of the organisms that White and other microbiologists have been able to identify, scientists can now grow about  20 percent of them. “The fundamental question I’m asking is: Is there an enzyme in the rumen that would work really well—really, really well?” White said. “We can now assess genetic information for organisms we can’t even culture.  It’s a case of: ‘Even if I don’t know who (what) you are, I can get your DNA. And, if I can get your DNA, I can reproduce it.’ This is genome mining or metagenome mining.”

He went on to explain that such mining can be done in one of two ways: by feeding ruminant animals (cows) the substrate the researcher is interested in breaking down and then analyzing the enzymes found in the cow’s manure. The other is called “rumen fishing” in which scientists put the substrates (plant material) for which they want to identify Nature’s choice for deconstruction in a nylon bag and toss it right into the cow’s rumen through a fistula or permanent opening in the cow’s side. Later, the nylon bag is removed so microbiologists can analyze which enzymes are at work breaking down the particular crop that was in the bag.

“The rumen is anaerobic (lacking oxygen) and is the most efficient place on Planet Earth to break down cell walls. About 30 percent of what goes in (what the cow eats) is broken down. But now, in the lab, I can get a breakdown of 75 to 80 percent. So, now we’ve got nearly double the number of enzymes and we’re getting a break down that is almost twice what we consider to be the best found in Nature,” White said. “What we’re putting together is really an incredible arsenal to break down plant walls and give us material suitable, ultimately, for making biofuels.”

White said the endgame for his research is to find either a tailor-made cocktail of enzymes that will work to break down any substrate of plant material or the most efficient cocktail for breaking down a particular substrate. He estimates that isolating either or both of these so-called cocktails or mixtures of enzymes will take five to 10 more years of research.

When asked if he predicts the same enzymes will work to break down cell walls of  different kinds of  biofuels crops—corn stover, miscanthus and other grasses, sugar cane, timber, etc., White said he was skeptical about identifying a universal solution. “When you look at the huge arsenal of enzymes in the rumen, I can’t believe that’s true. There would be no need for the rumen to continue to evolve with so many different enzymes if there was a ‘one-size fits all’ kind of answer for breaking down all of the different types of plants that cows ingest.”

White’s work is funded by the U.S. Department of Agriculture and the U.S. Department of Energy. Working with him is graduate student Margret Berg and Jennifer Brulc. Other collaborators are Karen Nelson, J. Craig Venter Institute; and Hans Blaschek, U of I Department of Food Science and Human Nutrition. Additional information about their work can be found on  White’s research webpage, http://www.nutrsci.uiuc.edu/faculty/profile.cfm?id=80, and on the U of I Institute for Genomic Biology webpage at: http://www.igb.uiuc.edu/research/biomass.html#top .

Writer Marilyn Upah Bant (217) 333-5724
Source Bryan A. White (217) 333-2091