Intestinal Bacteria and Probiotics ◾ 207
Prebiotics
The beneficial effect of probiotic bacteria depends on their presence in high numbers in the GI
tract. This can be achieved either by consuming a large number of viable cells of probiotic bacteria
or by stimulating rapid growth of desirable gut bacteria by supplying appropriate nutrients termed
as prebiotics. 19 Among the beneficial gut bacteria, Lactobacillus species are predominant in the
small intestine, whereas Bifidobacterium species are predominant in the large intestine (colon). An
approach has been taken to stimulate growth of Bifidobacterium in the colon by supplying one
or more selective carbon and energy sources that are not metabolized by the bacteria in the small
intestine as well as by many bacteria found in the colon. This gives Bifidobacterium a selective
growth advantage and allows it to reach high numbers. Prebiotics are defined as nondigestible
food ingredients that beneficially affect the host by selectively stimulating the growth or activity,
or both, of one or a limited number of bacteria in the colon, which can improve the host’s health.
Some of the nutrients that have gained importance as prebiotics are lactulose, lactitol, fructooligosaccharides, galacto-oligosaccharides, xylo-oligosaccharides, lactosucrose, pyrodextrins, and
inulin. Their actual effectiveness is currently being studied.
Synbiotics
The term “synbiotics” was coined to include both the terms “probiotics” and “prebiotics.” It is
assumed that instead of using probiotics and prebiotics separately, a product containing both, that
is, the beneficial gut bacteria in high numbers as well as nutrient supplements for them will enable
them to multiply rapidly in the gut and produce health benefits more effectively. This has to be
studied to determine their actual effectiveness.
Biogenics 20
The health benefit from the consumption of fermented dairy products is attributed to the lactic
acid bacteria used in fermentation as well as the byproducts of the metabolism of milk nutrients
by them. The latter aspect becomes important to explain health benefits attributed to fermented
products in which non-gut bacteria, such as Lactococcus lactis, Str. thermophilus, and Lactobacillus
delbrueckii ssp. bulgaricus, are used in fermentation. These products have recently been termed
“biogenics” and include components in food that are derived through the microbial metabolic
activity of food nutrients and have health benefits. One such group is the peptide produced by
the exoproteinases of some lactic acid bacteria, such as Lac. lactis in buttermilk and Lactobacillus
delbrueckii ssp. bulgaricus in yogurt. Some of the peptides thus produced and present in the fermented milk can reduce blood pressure in individuals with hypertension. This aspect is currently
being studied.
Genome Sequence of Probiotic Bacteria 21,22
The bacterial species and strains that are being studied for genome sequence include several
Lactobacillus, Bifidobacterium, Streptococcus, and Pediococcus species that are currently used as probiotic bacteria. These include Lactobcillusacidophilus, johnsonii, casei, gasseri, and rhamnosus; bulgaricus, plantarum, helveticus, lactis, Bif. longum, breve, and linens; and Streptococcus thermophilus.
The complete genome sequences are used to compare the genetic and functional diversities of the
GI tract beneficial bacteria, including adhesion traits, resistance to biles, bacteriocin production,
Prebiotics
The beneficial effect of probiotic bacteria depends on their presence in high numbers in the GI
tract. This can be achieved either by consuming a large number of viable cells of probiotic bacteria
or by stimulating rapid growth of desirable gut bacteria by supplying appropriate nutrients termed
as prebiotics. 19 Among the beneficial gut bacteria, Lactobacillus species are predominant in the
small intestine, whereas Bifidobacterium species are predominant in the large intestine (colon). An
approach has been taken to stimulate growth of Bifidobacterium in the colon by supplying one
or more selective carbon and energy sources that are not metabolized by the bacteria in the small
intestine as well as by many bacteria found in the colon. This gives Bifidobacterium a selective
growth advantage and allows it to reach high numbers. Prebiotics are defined as nondigestible
food ingredients that beneficially affect the host by selectively stimulating the growth or activity,
or both, of one or a limited number of bacteria in the colon, which can improve the host’s health.
Some of the nutrients that have gained importance as prebiotics are lactulose, lactitol, fructooligosaccharides, galacto-oligosaccharides, xylo-oligosaccharides, lactosucrose, pyrodextrins, and
inulin. Their actual effectiveness is currently being studied.
Synbiotics
The term “synbiotics” was coined to include both the terms “probiotics” and “prebiotics.” It is
assumed that instead of using probiotics and prebiotics separately, a product containing both, that
is, the beneficial gut bacteria in high numbers as well as nutrient supplements for them will enable
them to multiply rapidly in the gut and produce health benefits more effectively. This has to be
studied to determine their actual effectiveness.
Biogenics 20
The health benefit from the consumption of fermented dairy products is attributed to the lactic
acid bacteria used in fermentation as well as the byproducts of the metabolism of milk nutrients
by them. The latter aspect becomes important to explain health benefits attributed to fermented
products in which non-gut bacteria, such as Lactococcus lactis, Str. thermophilus, and Lactobacillus
delbrueckii ssp. bulgaricus, are used in fermentation. These products have recently been termed
“biogenics” and include components in food that are derived through the microbial metabolic
activity of food nutrients and have health benefits. One such group is the peptide produced by
the exoproteinases of some lactic acid bacteria, such as Lac. lactis in buttermilk and Lactobacillus
delbrueckii ssp. bulgaricus in yogurt. Some of the peptides thus produced and present in the fermented milk can reduce blood pressure in individuals with hypertension. This aspect is currently
being studied.
Genome Sequence of Probiotic Bacteria 21,22
The bacterial species and strains that are being studied for genome sequence include several
Lactobacillus, Bifidobacterium, Streptococcus, and Pediococcus species that are currently used as probiotic bacteria. These include Lactobcillusacidophilus, johnsonii, casei, gasseri, and rhamnosus; bulgaricus, plantarum, helveticus, lactis, Bif. longum, breve, and linens; and Streptococcus thermophilus.
The complete genome sequences are used to compare the genetic and functional diversities of the
GI tract beneficial bacteria, including adhesion traits, resistance to biles, bacteriocin production,