36 Part I: Principles
diseases and environmental stresses, allowing crops
to be grown in relatively unproductive and unsuit-
able land. Recent developments in biotechnology
will allow the production of more nutritious, safer,
tastier, and healthier food. Advances in genetic engi-
neering are revolutionizing the way we produce and
consume food, and it is quite possible that in the
next decade a large percentage of the food we eat
will be bioengineered.
In this review, the recent advances, methods, and
applications of biotechnology in the manufacture of
food products from transgenic plants, animals, and
microorganisms have been summarized. This article
is not, by any means, a documentation of every ap-
plication of biotechnology in the food industry, but a
comprehensive review, which includes the most rel-
evant examples. The results of important scientific re-
search trying to improve the nutritional value of sta-
ple crops such as rice, potatoes, and soybeans will
be discussed. This improvement can be achieved
through the introduction of genes that encode for
enzymes in the biosynthetic pathway of vitamins,
essential amino acids, essential elements, and mi-
cronutrient binding proteins. Examples of genetic
engineering of cattle, swine, poultry, and fish will be
described, with the purpose of improving milk qual-
ity, decreasing fat content, increasing productivity/
growth, and providing tolerance to freezing temper-
atures. The use of the mammary gland and egg as
bioreactors for the production of important proteins
will also be addressed. The third part of this arti-
cle will focus on the role of microorganisms for the
betterment of food products through the elimination
of carcinogenic compounds from beverages, the in-
hibition of pathogenic bacteria from starter cultures,
the production of healthier natural sweeteners, and
the synthesis of beneficial compounds such as carot-
enoids. Finally, some examples on the use of bio-
technology techniques in the detection of transgenic
material and harmful pathogens in food products
will be described. Other recent reviews of specific
aspects of food biotechnology will complement the
information provided in this article (Giddings et al.
2000, Kleter et al. 2001, Daniell and Dhingra 2002,
Dove 2002, Sharma et al. 2002, Taylor and Hefle
2002, Vasil 2003).
BIOENGINEERED PLANTS
Genetic engineering methods have been extensively
used to increase the quantity of different nutrients
(vitamins, essential amino acids, minerals, and phy-
tochemicals) and enhance their availability in plants.
There are two main methods for transferring genes
into plants for production of transgenic plants: Agro-
bacterium-mediated transformation and micropro-
jectile bombardment. In theAgrobacterium-mediated
transformation method, a genetically engineered
strain of Agrobacterium tumefaciens is used to
transfer the transgene into the plants. Some strains
of A. tumefacienshave the natural ability to transfer
a segment of their own DNA into plants for inducing
crown-gall tumors. These crown gall–inducing wild-
type strains of A. tumefacienshave a Ti (tumor
inducing) plasmid that carries the genes for tumor
induction. During the process of infection, Agrobac-
teriumtransfers a segment of Ti plasmid, known as
T-DNA, to plant cells (Willmitzer et al. 1983). The
Ti plasmid can be engineered into a two-plasmid (bi-
nary) system containing a “disarmed” Ti plasmid, in
which the T-DNA has been deleted, and a small
plasmid (referred to as a binary cloning vector) con-
taining an “engineered” T-DNA segment. The dis-
armed Ti plasmid, which is maintained in an A.
tumefaciensstrain, serves as a helper, providing the
transfer function for the engineered T-DNA, which
contains a target gene and a plant selectable marker
gene inserted between the T-DNA left and right bor-
ders. When the A. tumefacienscontaining the dis-
armed Ti plasmid and the binary cloning vector is
grown in the presence of acetosyringone, the Agro-
bacterium vir(virulence) gene proteins, which help
transfer the engineered T-DNA region of the binary
cloning vector to the plant cells, are produced (Zam-
bryski 1988). The Agrobacterium-mediated trans-
formation is the most commonly used method for
genetic engineering of plants.
The microprojectile bombardment method, also
known as the gene gun or biolistic transformation
method, involves the delivery and expression of for-
eign DNA directly into individual plant cells (Klein
et al. 1987). It has been proven to be a powerful
method for transforming a large number of plant
species, including monocots, which are often diffi-
cult to transform usingA. tumefaciens(Vain et al.
1995). In this method, tungsten or gold spherical par-
ticles, approximately 4m in size, are coated with
DNA and then accelerated to high speed and inserted
into plant cells using a biolistic particle delivery sys-
tem or a gene gun. Once the DNA gets inside a cell,
it integrates into the plant DNA through some
unknown process. It is not known whether integra-