Agriculture Reference
In-Depth Information
nonruminant animal feed, many ethanol produc-
ers plan to convert the fi ber in cereal grain or
DGS into ethanol, which can increase ethanol
yield and increase the value of DGS as a protein
supplement. Genetically engineered yeast (Ho
et al., 1998) and bacteria (Alterthum and Ingram
1989; Zhang et al., 1995) have been constructed
to co-ferment both C5 and C6 sugars from ligno-
cellulosic hydrolysates. Some pilot-scale and
demonstration tests have been conducted using
these engineered organisms, with promising
results (Dien et al., 2003; Van Maris et al., 2006;
Tsantili et al., 2007). Improvements are still
needed before being used in commercial ethanol
production.
2006). Integrated technologies have proven com-
mercially viable (Bryan 2005; Lewis 2007) and
should lead to higher ethanol yield, increased
nutrient quality and fl owability of dried DGS,
lower plant emissions, and reduced energy costs
by up to 15%.
FUTURE PERSPECTIVES
The future of wheat as a crop throughout the
world depends on the value it can bring to the
grower per unit of land on which wheat is grown.
Hard white wheat is recognized as having higher
demand in the world market. Wheat producing
regions should expand HW production in the
future and develop segregation mechanisms
throughout the value chain.
Applications of altered amylose-to-amylopec-
tin ratios in wheat fl our offers a new area for food
ingredients to replace many chemically modifi ed
products used today in the food industry. For
example, use of high-amylose resistant starch may
help formulate foods with lower glycemic index.
Reduction of enzyme systems, such as polyphenol
oxidase, may offer additional value in food systems
required to maintain a stable, light color. Reduc-
tion of phytate levels in wheat bran may offer
additional value in animal nutrition applications
to enhance mineral absorption.
Whole-grain foods are becoming more popular
as consumers realize the health value of micronu-
trients in these foods. More information on
micronutrient content of wheat will lead to con-
sumers associating nutrition with grains and will
motivate breeders to enhance these components.
Future wheat cultivars may have higher levels
of target nutrients, and new ingredient concen-
trates from wheat will be available for food
formulation.
Efforts to develop new sources of bioenergy
will dominate much of the plant breeding activity
in future decades. Wheat may play a role. Waxy
wheat starch converts to ethanol faster than other
starch. Wheat with lower protein and higher
starch contents, in which the starch is waxy,
would improve the potential of wheat as a grain
feedstock for ethanol. High-starch cultivars have
Processing technology
New cereal cultivars with high ethanol yield, such
as high total fermentables (HTF) from Pioneer
Hi-Bred International, Inc. and high fermentable
corn (HFC) from Monsanto Company, have been
developed and introduced into the market.
These new cultivars increase ethanol yield from
409 L t
−1
to 432 L t
−1
(Rendleman and Shapouri
2007). Fractionation of coarsely ground cereals
into bran, germ, and endosperm parts not only
expands the co-product profi le and increases the
value of co-products, but also increases the starch
content of the feedstock used for ethanol produc-
tion, thus indirectly enhancing production capac-
ity of the ethanol plant (Wang et al., 1997; Karl
et al., 2007).
Most energy consumption in an ethanol plant
occurs in the cooking process during liquefaction
and distillation, which accounts for up to 25% of
the total production cost of ethanol. Raw starch
saccharifi cation not only greatly reduces the
energy cost of ethanol production but also sig-
nifi cantly lowers the content of residual sugar,
organic acids, and glycerol in the spent grains. It
also increases protein content and improves
protein quality of DGS (Lewis et al., 2004; Lewis
2007). The claim was recently made for suc-
cessful integration of fractionation (the BFrac
process) with raw starch saccharifi cation (the
BPX process using an acid fungal amylase from
Novozymes, Bagsværd, Denmark) in several
newly built dry-grind ethanol plants (POET
