Lactobacillus bulgaricus

Yogurt is a semisolid food product of milk, after being fermented by added bacteria cultures. Yogurt is an easy way to obtain probiotic cultures, which improve lactose digestion, gastrointestinal functions, and stimulate the immune system. Humans and bacteria have a mutualistic relationship; both parties are entirely different but benefit from the relationship. There are millions of bacteria living in the inside and outside of us all!

 

 

 

 

 The most popular bacterial yogurt cultures used are Lactobacillus bulgaricus and Streptococcus thermophilus. The function of the bacterium is to ferment lactose, which is milk sugar, to produce lactic acid as a waste product. The increase of lactic acid present will decrease the pH of the milk, causing the liquid to clump and form yogurt.

The production of yogurt starts by adjusting the milk composition and adding the needed ingredients. Milk composition is adjusted to attain the preferred fat and solid content. In some cases, dry milk is added to increase the amount of whey proteins.  The milk mixture is then pasteurized at 85°C for 30 minutes or 95°C for 10 minutes. The increase in temperature will denature the whey protein; this will allow the proteins to form stable clumps. This prevents dissociation of the water and solid product during storage.

After being pasteurized, the milk mixture is homogenized to include the added ingredients entirely and improve the consistency. The milk is cooled at 42°C, which is an ideal temperature for Lactobacillus bulgaricus to grow. The milk is pasteurized before the cultures are added to ensure they will remain lively to act as probiotics. The yogurt will be held at 42°C until the pH has reached 4.5. This allows Lactobacillus bulgaricus and Streptococcus thermophilus to ferment the sugars present continuously. Fermentation is an anaerobic process, in which the final electron receptor is exchanged for another molecule. This process produces fermented end products such as lactic acid and ethanol. During the fermenting process, the milk will visibly clump together and start to resemble yogurt. After several hours of fermentation, the yogurt is cooled to 7°C to stop fermentation. Once the yogurt is completely cooled down, fruits and different flavors are added before packaging. Lactobacillus bulgaricus performing fermentation is a crucial step to yogurt production as well as other healthful foods.

Sources:

http://www.milkfacts.info/Milk%20Processing/Yogurt%20Production.htm

http://science.jrank.org/pages/710/Bacteria-role-bacteria-in-fermentation.html

https://prezi.com/aarmqkmdu_xf/human-and-bacteria-mutualism/

 

Reproduction 

Lactobacillus bulgaricus reproduces, like most bacteria, through binary fission. Binary fission is a form of asexual reproduction, in which a bacterial cell splits into two identical cells. The process of binary fission begins with the chromosome replicating and separating into two copies, while the cell body elongates. A septum begins to form in the middle of the newly elongated cell. The septum is where the parent cell will eventually split into the two daughter cells. Lactobacillus bulgaricus requires a low pH of 4.6 to 5.4 to grow and reproduce. In a recent study, the generation time was approximately 54 minutes at a temperature constant between 45- 55°C. 

Fermentation 

Lactobacillus bulgaricus is a heterotrophic, non-spore forming bacteria. Heterotrophic organism can not make their own food, they must obtain their energy from organic compounds. Lacto has complex nutritional requirements; they can not ferment any sugars except lactose. Lactose is their favorite and probably played a significant role in the naming. Lactobacillus bulgaricus is an anaerobic bacterium, which benefits fermentation. Anaerobic organism undergo cellular respiration without using the oxygen as the last electron carrier. Instead, anaerobic bacterium like Lacto use sulfur or nitrogen. Lacto eats the lactose in milk and release lactic acid as a waste product in yogurt. The added acidity cause the milk to thicken and clump up. The semisolid product gives the yogurt a tart taste. 

Acidic Properties 

Lactobacillus bulgaricus has an acid tolerance due to the constant gradient between extracellular and cytoplasmic pH. F₀F₁-ATPase is an enzyme that gram-positive organisms use for protection against acidic conditions. The F₀F₁-ATPase enzyme can induce at low PH and regulate the internal pH of the bacterium. 

References: 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1151822/

https://academic.oup.com/femsle/article/269/1/160/493589

https://sites.google.com/site/lactobulgaricus/repruduction

https://www.unboundmedicine.com/medline/citation/15071634/%5BThe_measurement_of_growth_curve_and_generation_time_of_lactobacillus%5D

http://dspace.bracu.ac.bd:8080/xmlui/bitstream/handle/10361/3037/10326008.pdf?sequence=1

Hello friends, 

I would like to introduce myself formally; my name is Lactobacillus Bulgaricus! I typically work within the human intestinal tract to aid digestion and prevent the attack of harmful viruses or bacteria, but I have a part-time job working as a fermenter and culture starter with food companies.

I belong to the genus Lactobacillus and a member of the Lactobacillus Delbrueckii species. I’m an anaerobic, single celled, non-motile, rod-shaped bacteria. I do not have a flagellum, but I twitch my body to glide through substances. My cell size ranges between 0.5-0.8 x 2.0-9.0mm, meaning I’m slim and petite. I’m also a member of the gram-positive community meaning my cell wall has a thick layer of peptidoglycan to preserve my perfect figure and anchors teichoic acids, some polysaccharides and surface proteins. My genome size is estimated by to be 2.3 Mbp by pulsed-field gel electrophoresis, along with a few plasmids I gained by conjugation through a few friends. My plasmids carry information that will help me become antibiotic resistance. My genome includes genes that encode for S-layer proteins used to create my slime layer. My slime layer helps me glide through different environments.

Thanks for tuning in,

Lacto 🙂

References used:

https://genome.jgi.doe.gov/portal/lacde/lacde.home.html

https://onlinelibrary.wiley.com/doi/full/10.1111/j.1574-6976.2009.00208.x#ss21-title

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3666127/

Here’s a video from the tour, I’m in the vans 🙂

I choose to visit Orpheus Brewery for my microbe site. There, I learned a lot about making beer; from the grains to the fermentation. Orpheus Brewery is located in Atlanta by Piedmont Park. When I walked in, the brewery seemed to be a typical bar, but as the tour started, I noticed I was entering a site of production. My tour guide, Liz, was very informative. I choose to study a microorganism called Lactobacillus Bulgaricus, and it belongs to the Lactobacillus genus.

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Lactobacillus Bulgaricus is a type of bacteria, that is commonly found in milk and yogurt. My tour guide compared the fermentation of beer to the fermentation of yogurt. I thought it would be cool to study this bacterium because it is a part of our normal flora as well.

Hello humans, 

I would like to give everyone a warm welcome to my lovely world. On this site, I will be giving you a glimpse of my life and my relationship with my awesome human, Aliyah. Stay tuned for exciting things!