Lactobacillus Bulgaricus: A Probiotic Strain

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Lactobacillus bulgaricus, also known as Lactobacillus delbrueckii subsp. bulgaricus is a member of the acidophilus group of lactic acid group of bacteria and Firmicutes phylum (1,2,3).

Lactobacillus delbrueckii subsp. bulgaricus is one of the subspecies of Lactobacillus delbrueckii along with Lactobacillus delbrueckii subsp. lactis, Lactobacillus delbrueckii subsp. delbrueckii, and the more recently discovered subspecies’ indicus, jakobsenii, and sunkii (3,4).

Lactobacillus delbrueckii subsp. bulgaricus is a Gram-positive, non-motile, non-spore forming, and rod-shaped bacterium, as are all Lactobacillus delbrueckii bacteria (1,4).

The Lactobacillus delbrueckii bacteria are also facultative anaerobic, which means that they can produce ATP (adenosine triphosphate), the primary energy carrier in all living things, in both oxygenated conditions, or through fermentation or anaerobic respiration in conditions lacking oxygen. Also, like other lactobacillus bacteria, Lactobacillus delbrueckii is acid tolerant and can survive the gastrointestinal tract (5,6).

According to a 2016 report on the genome sequence of Lactobacillus delbrueckii subsp. bulgaricus, researchers discovered a total of 251 subspecies of bulgaricus isolates from a collection of 298 Lactobacillus delbrueckii strains (1).

Genetically, Lactobacillus delbrueckii subsp. bulgaricus is closely related to other lactobacillus bacteria like L. amylovorus, L. acidophilus, L. helveticus, L. acetotolerancs, L. gasseri, and L. amylophilus, with less than a 10-percent difference between strains (4).

Also, the Lactobacillus delbrueckii subsp. bulgaricus bacteria has a somewhat higher ratio of GC (cuanine-cytosine) than other species of lactobacillus bacteria (about 34-46-percent) (4). The guanine-cytosine content of compounds has been directly linked with the temperature range condition of a prokaryotic organism (7).

Lactobacillus bacteria can adapt to temperature well, even in refrigeration temperatures as low as 4 to 7 degrees Celsius (2). The bacteria are not conducive to growth in such colder temperatures though but can remain metabolically active and survive.

One particular strain of Lactobacillus delbrueckii subsp. bulgaricus, Lb-87, is fairly resistant to acidic conditions and has a very good survival rate in the presence of bile (4). It also has a good adhesion to human intestinal mucus in vitro, which gives it the potential to be more effective in protecting the gut against enteric pathogens. It does this by limiting the pathogen’s ability to colonize the intestine.

Applications of Lactobacillus Bulgaricus

Lactobacillus delbrueckii subsp. bulgaricus have commonly been used in traditional Chinese fermented dairy products such as milk (8).

It is a common starter bacterium in the fermentation of commercial dairy products (1).

It is a homofermentative bacterium since it produces a single product because of fermentation, which in the case of Lactobacillus delbrueckii subsp. bulgaricus is D-lactic acid (9). It is widely used as a starter culture due to its ability to ferment in anaerobic environments such as in the lactose fermentation of milk.

In particular, the Lactobacillus delbrueckii subsp. bulgaricus strains BIM8 and BIM12 mutants show great potential as starter cultures in the dairy industry due to their phage resistance, or survival phenotype (8). Also, Lactobacillus delbrueckii subsp. bulgaricus LBB.B5-R shows growth in (soy) milk or whey by consuming lactose and other sugars like glucose (2).

This reveals milk to be a great medium in which to deliver Lactobacillus delbrueckii subsp. bulgaricus for optimal yield of the bacterium to the gut.

Lactobacillus delbrueckii is considered a probiotic due to research that revealed health benefits to the host after consumption of a yogurt produced with the bacterium and Streptococcus thermophilus (6,10).

The probiotic qualities of Lactobacillus delbrueckii subsp. bulgaricus are due to not only to the bacterial cells, but to their extracellular polysaccharides which aid in immune system properties such as cytokine production (11). In addition, the bacterium works well as a probiotic due to its ability to survive in the gastrointestinal tract (6).

Origins & Functions

Lactobacillus delbrueckii subsp. bulgaricus, like many lactobacilli bacterium, is found in fermented dairy products like yogurt and fermented milk. This bacterium is thought to originate in yogurt produced in the Balkan region of southeastern Europe in combination with Streptococcus thermophilus as well as from raw milk and plant material (12).

It’s suggested that the application of Lactobacillus delbrueckii subsp. bulgaricus in the preparation of fermented dairy products goes back thousands of years.

It has been identified as the main bacterial strain in certain kinds of fermented dairy products in China and Mongolia and is thought to have been in use as far back as 3800 years in Xinjiang, a northwest territory of China (1).

The milk proteins, lactose (milk sugar), lipids, and citric acid are degraded by the lactobacilli bacterium and give fermented milk products their distinct flavors (13).

Lactobacillus delbrueckii subsp. bulgaricus and related strains in this species are very specific to each strain (14) and include:

  • Immunomodulation, through the production of cytokines and other immune factors, which may be able to enhance host systemic immunity (2). An example of such function is revealed in a study that found potential application of Lactobacillus delbrueckii subsp. bulgaricus in controlling some strains of H. pylori infection (15).
  • Gut health protection through such processes as maintaining gut barrier function and reducing the symptoms of digestive disorders such as diarrhea, by strengthening the gut microbiome (2,16).
  • Detoxification properties (17).
  • Anti-inflammatory properties (18).

Potential health benefits

Lactobacillus bulgaricus is a widely studied bacterium and has been linked with a variety of health benefits.

Listed below are examples of the diverse range of applications that Lactobacillus bulgaricus has in the treatment of many aspects of health.

Digestive Health Benefits

Lactobacillus bulgaricus is widely known for its ability to improve health outcomes in gut health conditions.

Gut health benefits range from reducing gastrointestinal symptoms to reducing inflammation in those with painful digestive conditions.

A 2014 study looked at the effects of a probiotic containing Lactobacillus bulgaricus on pouchitis (19). Pouchitis is an inflammation of the intestinal mucosa of the small intestine that is a potential complication after restorative proctocolectomy, or removal of the rectum and all or part of the colon in those with inflammatory bowel disease.

Patients with pouchitis were treated with a probiotic containing Lactobacillus acidophilus, Lactobacillus delbrueckii subsp. bulgaricus, and Bifidobacterium bifidus. After nine months of treatment with the probiotic, the average severity of pouchitis and number of patients with pouchitis significantly decreased as compared to the placebo group.

Furthermore, the European Food Safety Authority approved the validity of the claim that yogurt cultures prepared from Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus can provide improved lactose digestion in those with lactose intolerance (20).

Other potential digestive health benefits include:

  • Lactobacillus delbrueckii subsp. bulgaricus increased secretory immunoglobulin A levels, and in turn decreased intestinal pathological damage (21).
  • Lactobacillus delbrueckii subsp. bulgaricus and other lactic acid bacteria reveal preventive effects on mouse constipation, and therefore may show potential for treatment of similar gastrointestinal conditions in humans upon further study (22).

Anti-Inflammatory and Immunomodulatory Benefits

Lactobacillus bulgaricus has been found to have some potential impact on various inflammation-related health conditions.

One example of that is regarding atopic dermatitis, an inflammatory skin disease. A cell culture study using immune cells were treated with Lactobacillus bulgaricus cells (23). After 48 and 72-hour treatments, study results show that Lactobacillus bulgaricus may control the secretion of various cytokines in atopic dermatitis patients, therefore showing that the bacterium may be a potential treatment of the skin condition upon further study.

Other research on potential anti-inflammatory and immunomodulatory benefits of Lactobacillus bulgaricus include:

  • Lactobacillus delbrueckii subsp. bulgaricus LBY-2 has shown to improve several inflammatory and oxidative stress biomarkers in women with gestational diabetes mellitus (24).
  • Lactobacillus species such as Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus rhamnosus, and Lactobacillus paracasei show potential for reducing Salmonella colonization in chickens (25).
  • The Golden Bifido probiotic mixture containing Lactobacillus delbrueckii subsp. bulgaricus, Bifidobacterium, and Streptococcus thermophilus (LBS) reveals a preventive role against E. coli K1 bacteremia and meningitis (26). It does this by enhancing the neonatal intestinal defense and could potentially be effective against other infections besides E. coli.

Food Safety

Lactobacillus delbrueckii subsp. bulgaricus G-LB-44 added to juice products helped reduce the growth of harmful bacteria such as Listeria, E. coli, and Shigella (27). The ability of the bacterium to do this is thought to be related to protein substances called bacteriocins that give one organism the ability to prevent the growth of another organism.

Another study shows that Lactobacillus delbrueckii bacteria in general could have an antifungal effect against the pathogens Penicillium notatum and Aspergillus fulvous (28). Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus was also found to be an effective antimicrobial agent in the production of goat’s milk (29).

Infection Control

Septic rats infected with Escherichia coli and Staphylococcus aureus had improved survival after treatment with a probiotic mixture containing Lactobacillus bulgaricus, Bifidobacterium longum, and Streptococcus thermophilus (30).

Another study looked at elderly persons and the impact of probiotics on flow rate of saliva (31). After 12 weeks of treatment with 112 grams of yogurt containing Lactobacillus delbrueckii subsp. bulgaricus OLL1073R-1 every morning, the mucosal immune function was improved.

These results suggest that by increasing the saliva flow rate, the probiotics helped prevent submucosal attack of pathogens, which in turn can reduce risk of catching colds (31,32).

Furthermore, Lactobacillus delbrueckii subsp. bulgaricus, along with Streptococcus thermophilus was tested in cases of Heliobacter pylori (33). Study results show that adding the bacteria before or after infection treatment may help improve H. pylori eradication rates.

Other potential applications:

  • In a 2013 study, rats were fed either a normal or high cholesterol diet, and those on the high cholesterol diet were given drinking water with either no probiotic, Lactobacillus plantarum NS5, or Lactobacillus delbrueckii subsp. bulgaricus NS12 (34). Those rats on the high cholesterol diet that were given either of the probiotic strains had decreased serum total cholesterol, low-density lipoprotein (LDL or “bad”) cholesterol, apolipoprotein B (the main protein component of LDL cholesterol), free fatty acids, and increased apolipoprotein A1 (the main protein component of high density lipoprotein (HDL or “good”) cholesterol).
  • A 2018 study looked at the effects of yogurt containing Lactobacillus delbrueckii subsp. bulgaricus OLL1073R-1 on summer heat fatigue (35). Study results show that after ingesting 100mL of yogurt daily for 12 weeks in the early autumn, visual analogue scores (VAS) (a response scale used in questionnaires) for fatigue were lower than the placebo group. This suggests that the bacterium may help to reduce summer heat fatigue lasting until the early autumn.
  • A 2017 study looked at the effect of probiotics on a myocardial infarction rat model (36). Pretreatment of rats induced with a myocardial-like infection with probiotics including Bifidobacterium breve, Lactobacillus casei, Lactobacillus acidophilus, and Lactobacillus delbrueckii subsp. bulgaricus significantly reduced lipid peroxidation and improved cardiac function. These results show that certain probiotics could potentially have a cardioprotective effect on those with heart disease, upon further study.
  • Lactobacillus delbrueckii subsp. bulgaricus may be used in the treatment of immunodeficiency disorders (37).
  • A 2016 study looked at the impact of a synbiotic containing Lactobacillus casei, Lactobacillus rhamnosus, Streptococcus thermophilus, Bifidobacterium breve, Lactobacillus acidophilus, Bifidobacterium infantis, and Lactobacillus delbrueckii subsp. bulgaricus on asthmatic children (38). Study results show that this synbiotic plus fructooligosaccharide, a type of sugar, shows potential to reduce episodes of viral infection in asthmatic children.

Form of Taking Lactobacillus Bulgaricus

Aside from being consumed in the form of fermented food products such as yogurt, cheese, and fermented milk, Lactobacillus delbrueckii subsp. bulgaricus can also be consumed in capsule or capsule form.

Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus salivarius subsp. thermophilus are used to create Akcakatik semi-hard and sour yogurt cheese as well as traditional Indian yogurt and Dosa (37,39).

Various studies have looked at effective ways to maintain viability of the bacterium under storage conditions.

One study looked at the L. acidophilus and Lactobacillus delbrueckii subsp. bulgaricus counts of yogurt prepared with or without a commercial plant extract (40).

This commercial plant extract was prepared from olive, garlic, onion, and citrus extracts with a sodium acetate carrier. After 29 days of storage at 5 degrees Celsius, the yogurt supplemented with the plant extract had greater L. acidophilus and Lactobacillus delbrueckii subsp. bulgaricus counts then those not supplemented with the extract.

Another study looked at ways to maintain viability of Lactobacillus delbrueckii subsp. bulgaricus in capsule form.

Higher viability was found in freeze-drying the bacterium in a medium such as skim milk in water or skim milk and trehalose, which is a sugar consisting of two molecules of glucose (41).

This medium was most effective when combined with a cryoprotectant such as sodium ascorbate, which is a mineral salt of citric acid. As a result, there was a decline in viability that occurred in samples stored at 23 degrees Celsius versus those stored at 4 degrees Celsius.

Possible Side Effects

Lactobacillus bulgaricus has been used in health food products for many decades, so is considered to be safe for human consumption (4).

The European Food Safety Authority (EFSA) added the species to the Qualified Presumption of Safety (QPS) list as well as the Generally Recognized as Safe (GRAS) list by the U.S. Food and Drug Adminstration (4,42,43).

In vitro, Lactobacillus bulgaricus is found to have very low gelatinase activity, which is a marker showing damage to the gums (4). Therefore, you can assume it’s safe for gingival health. Similarly, studies have shown that Lactobacillus bulgaricus strains used in yogurt production are not proteolytic, or protein-degrading, and showed very low gelatinolytic activity (44). Therefore, the bacterium is not likely to degrade host tissue.

Taking this information into account, as well as the fact that strains of Lactobacillus bulgaricus have been safely used in foods for over 100 years with no significant adverse effects, the bacterium can be considered safe for human consumption (27,45).

What to Look for When Buying Lactobacillus Bulgaricus

If you think you would benefit specifically from taking lactobacillus bulgaricus, make sure to check the label for it, as not all probiotic supplements contain this strain.

As always, once you’ve found a supplement containing this strain or any other strain you think would be beneficial, do your due diligence on the brand to make sure the product is effective and meets safety standards.

Also, consuming probiotic-rich foods in their purist form can provide you with an unadulterated dose of Lactobacillus bulgaricus.

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