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Corn Cobs on the Job

This post is part of the Science Tuesday feature series on the USDA blog. Check back each week as we showcase stories and news from USDA’s rich science and research portfolio.

If you’re of a certain age, you might remember General Douglas MacArthur’s famous corncob pipe, or the one sported by “Granny” on the hit TV show “The Beverly Hillbillies.” But aside from those picturesque examples, corncobs have tended to mostly be considered a waste product left over from the harvest of the golden, juicy kernels of corn.

That’s in the process of changing, thanks to the scientists of the Agricultural Research Service (ARS).  For starters, they’ve shown that corn cobs left in the field after harvest can boost soil quality.  Beyond that, those tough cobs can be used to make a whole host of products.

ARS scientists have now discovered “overachiever” yeast that breaks down and ferments the sugars that are left behind in the corncobs after the xylose has been extracted.  This works even without the addition of a costly enzyme, a breakthrough that could help make cellulosis ethanol production a cost-effective proposition.

Molecular biologist Z. Lewis Liu (right) and technician Scott Weber add a new yeast strain to a corncob mix to test the yeast’s effectiveness in fermenting ethanol from plant sugars.  The yeast naturally produces an enzyme that helps release and degrade sugars from biomass, and that could help reduce ethanol production costs.

Molecular biologist Z. Lewis Liu (right) and technician Scott Weber add a new yeast strain to a corncob mix to test the yeast’s effectiveness in fermenting ethanol from plant sugars. The yeast naturally produces an enzyme that helps release and degrade sugars from biomass, and that could help reduce ethanol production costs.

The newly identified yeast strain resists corncob compounds that can interfere with yeast growth and fermentation rate. What’s more, it can grow at hotter temperatures, up to 98 degrees Fahrenheit, which means it can thrive at the higher temperatures needed to complete the process of releasing and fermenting feedstock sugars for biofuels.

But its biggest plus is that it comes equipped with its very own version of an enzyme called beta-glucosidase, one of two expensive enzymes that now must be added to the mix for ethanol production from cellulose.  Since biofuel producers don’t have to add that enzyme in the process because the yeast already provides it, that cuts the overall cost of biofuel production from cellulosic feedstocks like corncobs.

In tests, the newly identified yeast, dubbed Y-50464, more than doubled the output of a competitor yeast at cranking out ethanol even without the addition of the critical beta-glucosidase.  The scientists say this unique new yeast strain could be the key to more cost-effective bioprocessing for advanced biofuels production.

One Response to “Corn Cobs on the Job”

  1. William (Spence) Shore, says:

    The combines normally grind the cob to the the rest of the stover. Harvesting the ground cobs should mix with the corn?

    Spence Will the yeast produce ethanol from the stalks?

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