Monitor Bt Protein in Corn Ethanol
By Jan Suszkiw
July 5, 2002
Protein from the soil bacterium
Bacillus thuringiensis has earned much praise for its environmental and
economic benefits as a natural pesticide. But less well known is what happens
to the protein in Bt-modified corn when processed into ethanol.
To find out, Agricultural Research Service (ARS) chemical engineer Bruce Dien and
colleagues designed small-scale experiments with wet- and dry-milled Bt
corn hybrids that enabled them to monitor the protein during all stages of
According to Dien, with ARS National Center for Agricultural Utilization
Research in Peoria, Ill., theres been little prior research delving
into Bts effects on ethanol even though Bt-modified corn
accounts for roughly 25 percent of the U.S. crop.
Bt corn contains genes from the bacterium for making the protein as a
built-in pesticide against the larvae of European corn borers. At each stage of
their experiments, Diens team checked for the presence and amount of
the Bt protein, CRY1Ab, using an antibody-based test called an
Enzyme-Linked Immunosorbent Assay.
During dry milling, they found, the use of heat to liquefy corn meal quickly
destroyed the protein, and there was no detectable trace of it in either the
mash or resulting ethanol. In wet-milled corn, they detected Bt in whole
kernels, gluten, germ oil and fiber at concentrations of 170 to 453 parts per
billion. But nothing turned up in the starch or steep liquor fraction, used to
produce the ethanol.
Ethanol yields from Bt corn also matched that of non-Bt
hybrids. Typical industrial ethanol yields are about 2.7 gallons per bushel via
dry-milling and 2.5 gallons for wet-milled corn.
More details about these studies, including new findings on the role of corn
starch on ethanol yields, appear in this months issue of Agricultural
ARS is the U.S. Department of
Agricultures chief scientific research agency.