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Prebiotics
The term "prebiotic" means a substance that
encourages existing microflora to increase its
population. Prebiotics differ somewhat from
probiotics, in that a prebiotic substance may
consist of an enzyme, component, or chemical
extracted from a particular strain of bacteria,
or from a fermentation reaction involving
bacteria. When prebiotics are found to be
effective, the purpose they serve is that of a
catalyst to promote the growth of the host's
indigenous colonies of helpful bacteria. A
simple way to remember this is that a prebiotic
prepares the way for a probiotic. Prebiotics do
not act in isolation, they do not introduce new
bacteria, and they typically do not contain an
entire culture of bacteria. Prebiotic substances
often consist of high-tech laboratory extracts
derived from bacteria, wherein a particular
chemical reaction or component of bacteria has
demonstrated effectiveness in encouraging the
activity of surrounding micro-organisms.
Over the past ten years, the field of
microbiology has mapped the genomes of many
strains of bacteria, while studying the
metabolism and behavior of helpful microflora
such as Bifidobacteria and Lactobacillus. By
adjusting lab-produced fermentation processes,
it has been observed that probiotics or helpful
bacteria become more active when certain
chemicals or prebiotics are present. A frequent
subject of study is the chemical called "GOS,"
which is short for Galactooligosaccharide(s).
An oligosaccharide is a short chain of
sugar molecules, where as Fructo-oligosaccharides
(FOS) consist of short chains of fructose
molecules. Inulin is another prebiotic
that also consists of short chain fructose
molecules and both are often derived from
vegetables. These compounds
can be only partially digested by humans, but
the undigested portion offers life sustaining food
for certain
probiotics. Various mixtures of GOS, including natural and
cloned or synthetic products have proved to be
effective prebiotics. GOS and other
oligosaccharides appear to boost the growth rate
of surrounding bacteria, in laboratory, animal,
and human studies.
Because breast-feeding of infants has been
proven for many years to enhance the
establishment and growth of beneficial
microflora in the GI tract, many studies have
sought to identify the exact substances that
give breast milk its immune system advantages.
Once identified, the chemicals that create a
prebiotic or bifidogenic effect may be applied
in the production of other food-related
products, such as immune-boosting supplements
for people with illnesses related to microflora
imbalance. A 2008 study by Boehm and Moro cited
in "The Journal of Nutrition" aimed to mimic the
positive effects of breast-feeding on the growth
of microflora. Although the prebiotic and
probiotic aspects of breast milk are attributed
to dozens of substances, oligosaccharides appear
to be an optimum fuel for intestinal microflora.
The Boehm and Moro study found that including
oligosaccharides in infant formula can mimic
some of the positive effects of breast milk, in
terms of providing a preferred prebiotic that
enhances the colonization rate of beneficial
microflora. A similar study in 2008 by R.
Gonzalez and E. S. Klaassens upheld the idea
that the bifidogenic properties of human milk
are related to its oligosaccharide content. The
Gonzalez study used a cloned or semi-synthetic
medium containing GOS, which contains a large
amount of lactose and galactose, comparable to
human milk. By exposing the synthetic material
to B Longum bacteria and observing its reaction,
this study drew many parallels between simulated
GOS and the carbohydrate-utilization genes
present in human milk. In order to optimize
infant formula, and applications for other
food-related products, these studies provide
insight into the mechanisms needed to produce
effective prebiotics.
A 2009 study by Pokusaeva and O'Connell-Motherway
correctly hypothesized that particular isomers
of sucrose would enhance the hydrolytic activity
of certain genes within a strain of
Bifidobacterium. The genes they isolated
performed the function of encoding glucosidase.
These particular genes are affected
significantly when optimal pH levels and
temperature are adjusted. Studies such as this
have helped to identify which substances and
environments are most helpful in encouraging the
growth of helpful bacteria, and what chemicals
are effective as prebiotics to prepare an
optimal environment for microfloral growth.
How are new prebiotics discovered and tested?
Some studies of the substance called GOS
indicate that a galactosyltransferase chemical
is combined with lactose and a strain of
Bifidobacterium Bifidum to produce new
oligosaccharide mixtures. Sometimes the mixture
is observed in vitro, and sometimes it is
introduced to animals for "in vivo" trials, in
order to assess the prebiotic effects of a
particular substance. If successful, animal
trials are eventually followed by human trials
in the testing of a particular prebiotic.
Both approaches were used in a 2008 study by
Depeint and Tzortzis, as cited by "The American
Journal of Clinical Nutrition." Their study
produced an effective prebiotic made from a
newly developed oligosaccharide mixture which
significantly increased the Bifidobacteria and
Lactobacillus populations in human and animal
subjects. During this trial, oligosaccharides
also appeared to inhibit the growth of E coli
and salmonella within the colon of the subjects.
The oligosaccharides, when added to the
subjects' diet, also increased the concentration
and density of Bifidobacteria. Prior to testing
with human subjects, the same research team
performed a variety of studies on pigs, to
ascertain their microfloral reaction to various
oligosaccharide mixtures.
Studies in the field of prebiotics offer a
glimpse into the future of food production,
genetics, applied microbiology, and new medical
applications. Whereas probiotics use various
forms of existing bacteria, prebiotics tend to
isolate components of those cultures and
manipulate certain genes to optimize their
microfloral functions. When teamed together, a
prebiotic substance such as GOS has been shown
to create a welcoming environment prior to the
ingestion of a probiotic formula. Many
formulas utilize FOS and Inulin as prebiotics
with great success at increasing the viability
and longevity of the probiotic formula. Some
prebiotics are used without probiotic
supplements, and still show a benefit to the
indigenous microflora of the host. Future
studies in the field of prebiotics may identify
which form of oligosaccharide is preferred by
each strain of microflora, in order to maximize
the accuracy of probiotic medicinal benefits. If
each of the GI tract microflora which are
beneficial to human health could be optimized
and nurtured by the use of a designated
prebiotic, the potential to prevent and reduce
diseases would be significant.
SOURCES:
- G. Boehm and G. Moro. "Structural and
Functional Aspects of Prebiotics Used in Infant
Nutrition." Journal of Nutrition, September 1,
2008; 138(9): 1818S - 1828S.
- R. Gonzalez, E. S. Klaassens, E. Malinen, W.
M. de Vos, and E. E. Vaughan. "Differential
Transcriptional Response of Bifidobacterium
longum to Human Milk, Formula Milk, and
Galactooligosaccharide (GOS)." Applied
Environmental Microbiology. August 1, 2008;
74(15): 4686 - 4694.
- K. Pokusaeva, M. O'Connell-Motherway, A. Zomer,
G. F. Fitzgerald, and D. Van Sinderen.
"Characterization of Two Novel alpha-Glucosidases
from Bifidobacterium breve UCC2003." Applied
Environmental Microbiology, February 15, 2009;
75(4): 1135 - 1143.
- F. Depeint, G. Tzortzis, J. Vulevic, K.
I'Anson, and G. R Gibson. "Prebiotic evaluation
of a novel galactooligosaccharide (GOS) mixture
produced by the enzymatic activity of
Bifidobacterium bifidum NCIMB 41171, in healthy
humans: a randomized, double-blind, crossover,
placebo-controlled intervention study." American
Journal of Clinical Nutrition, March 1, 2008;
87(3): 785 - 791.
- T. M. Hill, H. G. Bateman II, J. M. Aldrich,
and R. L. Schlotterbeck. "Oligosaccharides for
Dairy Calves." Professional Animal Scientist,
October 1, 2008; 24(5): 460 - 464.
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