The Virginia Tech and USDA researchers decided to go after the most common mycotoxin in barley, deoxynivalenol (DON).
Previous research on a fungus (Fusarium graminearum) that produces DON in barley has identified several genes that convert trichothecenes to less toxic products. The research team selected two of these genes (TRI101 and TRI201), introduced them into a laboratory yeast strain (RW2802), and compared the results to commercial yeast that has been optimized to produce fuel ethanol. The researchers fermented four varieties of barley that Griffey's team created for biofuel use, hulless Eve and VA06H-25 and hulled Thoroughbred and Price.
Measurements of the resulting mash and animal feed revealed that DON had indeed been converted to a less toxic form (3ADON) during fermentation, with the transgenic yeast expressing either TRI101 or TRI201. The researchers wrote, "We found large reductions in DON via conversion (52.4 percent to 58.1 percent) during fermentation of the hulless barley line VA06H-25, which contained the highest levels of DON in its starting ground grain."
"But in all cases, using the yeast with the added genes resulted in decreased DON as it was converted to the less toxic form (3ADON)," said Khatibi.
"To our knowledge, this is the first detailed report of yeast expressing a DON modification enzyme during barley ethanol fermentation," said Schmale.
Khatibi said, "This study sets the foundation for modifying mycotoxins during fermentation and provides a model for future work when we find an enzyme that can actually destroy the toxin."
The research was supported by Schmale and Griffey's grants from the USDA, Virginia Agriculture Council, and M
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