Biomedical Engineering Reference
In-Depth Information
Genetic Engineering
Genetic engineering has potential to expand the functionality of starch dramati-
cally. As mentioned previously making waxy or amylose-extender dominant would
greatly facilitate breeding efforts, it simplifies backcrossing, reducing testcrossing
and trait verification self-pollination steps.
A transgenic amylose-extender that includes an enhancing modifier construct
would reduce breeding difficulties in dealing with independently segregating mod-
ifiers. Resequencing the promoter code of starch biosynthetic genes to upregulate
expression can effectively increase starch content [
66
]. Another highly interesting
use is gene sequencing and genomic comparisons, genes from different species can
be used for comparison purposes, and potentially maize genes could be altered to be
more like those of cassava or potato.
Cassava differs greatly from corn in functionality and granule structure, and the
genetics behind these differences may be transferable. Some aspects of the root and
tuber starches are a result of starch development in the subsoil environment. It
would be very interesting to better understand the associated genetic contributions
of characteristics like the increased phosphate content observed in potato starches.
The Enogen
transgenic event and other similar approaches have a high poten-
tial for reward but also a significant risk component. The ethanol industry is a
multibillion dollar industry; capturing even a portion of that market could be very
lucrative. The risks, however, include the possibility that the event escapes grain
channels and enters the food or other non-approved markets. The StarLink
®
corn
recall is a stark example of that risk and has been estimated to have cost the Aventis
company and US corn producers hundreds of millions of dollars [
67
].
Given that risk can be managed, it would be very interesting to consider the
possibilities of including branching enzymes or other proteins that could be acti-
vated postharvest in the starch manufacturing stage. The proteins could be embed-
ded in the granule and activated during wet milling, starch drying, or through a
specialized manufacturing step. Starch chains could be broken and reformed to
provide cross-linking, improving granule integrity and resistance to sheer, heat, or
other stresses. Such an approach could greatly impact starch chemical modification
and potentially provide safe and sustainable materials for many unique industrial
starches.
™
Commercial and Foundation Seed Production
Seed production for specialty maize is much like that used in production of other
commercial corn seed; however, because of the very specific end use of waxy and
amylose grain, control and reduction of seed contamination are priorities. Com-
mercial dent seed production requirements include an isolation distance of not less
than 660 ft from any other corn, greater than 99 % of seed parents must be
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