"Superenzymes" Could Streamline Biofuels Refining

By Marcia Wood
October 22, 2008

Stain removers that make even the most stubborn spots on your clothes vanish in the wash may be powered by molecules known as enzymes. Agricultural Research Service (ARS) scientists at Albany, Calif., are in search of similarly strong, fast-acting enzymes. But the ones they want would be put to work not in your laundry room, but instead at biofuels refineries, where the enzymes' job would be to break down the cell walls of bioenergy crops such as switchgrass.

The tight matrix of compoundscellulose, hemicellulose, and ligninin the walls of switchgrass cells is difficult for familiar enzymes to disassemble. That's a factor that makes refining cellulosic ethanol more costly and complex than making ethanol from starch.

The search for enzymes that excel in degrading plant cell walls has led Albany research chemist Charles Lee, with the ARS Bioproduct Chemistry and Engineering Research Unit, to probe dank soil beneath 25-foot-high piles of decaying rice straw, and to carefully draw samples of murky liquid from dairy-waste lagoons.

Back at the lab, Lee and colleagues scrutinize these and other samples—a miscellany of anonymous microbes—to determine whether any of them contain genes that have the blueprint for enzymes of interest.

From one dairy lagoon sample, they found a microbe with a gene that they've named xyn8. It contains the blueprint for a xylanase, an enzyme that specializes in breaking down xylan, a troublesome component of the hemicellulose in plant cell walls.

But there's even more to like about this xylanase: It works well in temperatures regarded as "cold" in the biofuels business. Cold-loving xylanases would sidestep the need for the costly heating typically needed at today's biorefineries.

Read more about the research in the October 2008 issue of Agricultural Research magazine.

ARS is a scientific research agency of the U.S. Department of Agriculture.