As long ago as 1907, when Russian biologist and
Nobel Prize winner Elie Metchnikoff wrote about
longevity research in his book The Prolongation
of Life, the bacterial strain Streptococcus
thermophilus was known to promote
gastrointestinal health. Streptococcus
thermophilus, along with Lactobacillus
bulgaricus, soon became the starter strains used
to make yogurt. Today, these two probiotics are
still used in the production of true yogurt.
Many of the yogurts sold in grocery stores are
not this true yogurt. Some do not use the
appropriate probiotic strains, as these are
usually more expensive. Some do, but still
pasteurize their product after the culturing
process. Pasteurization destroys harmful
bacteria, but it also destroys the beneficial
organisms such as Streptococcus thermophilus.
Consumers can look for the National Yogurt
Association’s Live & Active Cultures seal on
packaged yogurt. This means the product did
contain live cultures when it was made, although
it is no guarantee that the beneficial bacteria
will still be alive after shipping and storage.
By purchasing a starter of Streptococcus
thermophilus and Lactobacillus bulgaricus,
yogurt can be made at home with a simple recipe.
These probiotic cultures are available most
health food stores, online, and even in the
health food section of some grocery stores. Boil
one quart of milk, preferably 2% or whole milk,
then remove it from heat and cool to between 104
degrees and 114 degrees. It is important to use
a sterile container to pour the milk into. Add a
generous teaspoon—or the appropriate amount
listed on the package instructions—of the yogurt
starter. Stir, cover, and incubate at 104 to 110
degrees for six to ten hours. Refrigerate.
This constant incubation temperature is a very
important part of the process. Those that have
trouble maintaining this temperature might want
to consider purchasing a yogurt maker, which
The process behind this yogurt production is
beneficial to digestive health in a couple of
ways. The good bacteria ferment the sugar in the
milk, also known as lactose. The lactose is
transformed into lactic acid, which is highly
effective in preventing lactose intolerance. The
production of the lactic acid reduces pH and
results in the milk curdling and turning tart.
This also prevents the growth of bacteria that
causes food poisoning.
Streptococcus thermophilus is used as a starter
culture for dairy foods besides yogurt,
including Mozzarella cheese. It is considered
one of the most commercially important of the
lactic acid bacteria. USDA statistics from 1998
showed that more than 2.24 billion pounds of
Mozzarella cheese and 1.37 billion pounds of
yogurt were produced, for almost five million
dollars in consumer value. Today’s 40 billion
dollar dairy industry relies more and more on
Streptococcus thermophilus and other probiotic
The cell structure of Streptococcus thermophilus
allows the bacteria to endure elevated
temperatures, such as the many industrial dairy
fermentation processes that require high
temperatures. Streptococcus thermophilus also
lacks genes which contain surface proteins. This
is important because harmful bacteria use these
surface proteins to attach to mucosal tissues
and hide from the body’s defensive actions.
Ongoing research and experimentation have
improved the Streptococcus thermophilus strain
even beyond its natural beneficial state. This
improved strain is responsible for the
consistent taste and texture of many dairy
products. It also provides stable fermentation
and a resilience to bacteriophage.
Streptococcus thermophilus also produces
exopolysaccharides. These are essential to the
texture of fermented milk products and also to
the production of reduced-fat dairy products
that maintain similar characteristics to their
full-fat counterparts. One of Streptococcus
thermophilus’ unique abilities is that it can
break down casein, the protein in dairy products
like cheese. It reduces them into small peptides
and amino acids that are required for the
maturation of textures and flavors in
reduced-fat cheeses. Different bacterial strains
produce cheeses with differing characteristics.
Streptococcus thermophilus, for example,
produces a low-moisture cheddar cheese with a
minimal level of bitterness, good for very mild
cheddar cheese. However, by combining bacterial
strains with varying characteristics, a high
quality, reduced-fat cheddar cheese may be
produced that is very similar to regular,
In addition to the natural ability of
Streptococcus thermophilus to prevent
transformation of nitrates into cancer-causing
nitrites, the bacterium has other exciting
cancer-related applications. One strain which is
undergoing exciting research is Streptococcus
thermophilus TH-4. Chemotheraphy often causes
intestinal mucositis, severe inflammation of
primarily the small intestines which can be
fatal. Although there are a variety of
treatments for this condition, they often do not
A 2009 study in Adelaide, Australia has shown
very positive results when Streptococcus
thermophilus TH-4 was used to treat rats with
mucositis caused by chemotherapy drugs. Rats
responded to the treatment by showing a
normalization of healthy cell function in the
affected areas and a significant reduction of
distress to the tissue of the intestines.
As research continues to produce varied strains
of Streptococcus thermophilus, the usefulness of
this probiotic seems limitless. Its effects on
digestive and overall health have already been
widely documented. Its benefits to cancer
patients undergoing chemotherapy are beginning
to be understood. Streptococcus thermophilus is
one of the many reasons probiotics are changing
the health industry.
Awad, S. et al. (2005). Journal of Dairy
Science. Application of Exopolysaccharide-
Producing Cultures in Reduced-Fat Cheddar
Cheese: Composition and
European Bioinformatics Institute. (2009).
Bacteria Genomes – Streptococcus Thermophilus.
Taylor, John R. and Mitchell, Deborah. The
Wonder of Probiotics. New York, NY: St. Martin’s
Trenev, Natasha. Probiotics: Nature’s Internal
Healers. Garden City Park, New York:
AveryPublishing Group, 1998.
U.S. Department of Energy. Office of Science.
(2009). Streptococcus thermophilus LMD-9.
Whitford, E.J. et al. (2009). National Center
for Biotechnology Information. Effects of
Streptococcus thermophilus TH-4 on Intestinal
Mucositis Induced by the Chemotherapeutic Agent,
5- Fluorouracil (5-FU).
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