Factors affecting the growth rate of Lactobacillus Casei

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Our world is diverse from plants, animal and humans. Even the smallest organism like the cell is every diverse. Today we know that there are a lot of species and genus of bacteria. We consider bacteria as a prokaryotic, which is a single celled organism and doesn’t have a nucleus. They come from different shapes and sizes. In terms of shapes they can either be a rod shape or spherical shape or spiral shape. We can classify spiral shape bacteria as campylobacter, rod shape as lactobacillus and spherical as staphylococcus.

Lactobacillus Casei is a bacteria species coming from the Lactobacillus genus. It has rod shaped gram-positive bacteria. It is consider as a probiotic, which means that they give out good nutrients to the body when they are consumed and are very beneficial to the human body. It is normally found in the human stomach or intestines, and is acid tolerant due to the high acidity of the human intestines. They can also be found in any dairy products like cheese and milk. They are able to survive in temperatures between 30°C to 40°C, which we consider as mesophilic organisms. It is also consider as a facultive anaerobic, which can either use oxygen in aerobic respiration in making ATP or can use anaerobic respiration like fermentation if oxygen is absent from the system. Lastly, lactobacillus casei is an organotroph, which means that these bacteria gain its energy from organic substances.

Lactobacillus Casei has many benefits, one of which is producing lactic acid that helps in lowering the PH of the digestive tract in turn stopping the growth culture of harmful bacteria found in its environment like in the stomach. Another benefit of the bacteria, is that it aids the low lactose intolerance which are experienced by some people. Lactose intolerance is experienced when a person cannot digest lactose normally, which is found in dairy products.

Lactobacillus Casei also helps people with Crohn's disease. The bacteria are able to resist or lessen the effect of the disease in their body. Crohn’s disease is an inflammatory bowel disease, wherein a person may experience low immunity in the gastrointestinal tract due to the bad pathogen culture in the stomach. This disease can be compared to a severe diarrhea in which a person may excrete blood from his/her anus. It also improves the insulin resistance, wherein a person’s body does not fully respond to the insulin produce and can lead to high glucose content in the body and if untreated can be a cause of obesity and diabetes. Lastly, it also fortifies the immune system from any bacterial growth in the digestive tract.

One of the exciting events in the history of this bacteria is its probiotic effects. In the year 1930, Dr. Minoru Shirota, working in the Kyoto Imperial University's School of Medicine was able to improve and culture lactic acid bacteria that we know today as Lactobacillus Casei Shirota. That time Japan was on a modernization period coming from years of isolation from the outside world. Japan was still using primitive ways in curing common illness like fever and diarrhea, which resulted into many complications to patients leading to deaths. In 1935, Dr. Shirota began incorporating Lactobacillus Casei Shirota to a fermented beverage that we know today as Yakult. In 1938, Yakult was registered as a trademark with Lactobacillus Casei as a main ingredient. Thru the years Yakult became of one of the main companies in Japan and still increasing to a worldwide scale.

Factors affecting the growth rate of Lactobacillus Casei

Lactobacillus is one of the largest genus within the lactic acid bacteria. This bacteria actually is the reason behind good hygienic quality of different products in the dairy industry. Also, these bacteria show probiotic effects, promoting healthy live cultures. These are some of the reasons why it is very important to know the different stresses that it experiences to be able for it to survive.

Lactobacillus casei, a bacteria, is greatly affect by its surroundings and would definitely react to a lot of external conditions like all organisms. This bacteria exhibits a lot of systems for sensing and adapting to different kinds of stressful conditions in order for them to survive. The general conditions that affect bacteria is the external stresses from the environment. This could be in a form of heat; the change of surrounding temperature or the cell growth itself which composes of starvation and acid stress. Generally, Lactobacillus casei is used as a probiotic and surely can be found in the intestines. Before it can make its way there, it would pass to the stomach, which comprises of a lot of destructive organisms, acids and enzymes, which affects its survivability. The environmental conditions in the stomach are extreme for the bacteria since it contains a high percentage of acid generated by the gastric juice. This creates an extreme acid stress for the bacteria. The different microbes also affects each other since they are constantly competing for available nutrients.

Heat and Cold Shock

One of the factors that affects the growth rate of lactobacillus casei is the introduction of heat shock or heat stress. According to researches, increasing or decreasing the temperature of the environment of the lactobacillus greatly affects it growth rate. Inducing heat shock decreased the survival of these probiotic bacteria pertaining to its original viability. This means that in order for the good bacteria to reach its target, it must survive the heat coming from different exothermic reactions happening in the digestive system. Introducing cold shock however, changes the cellular composition including its protein profiles. These mutant bacteria based from researches, showed a significant reduction in its growth rate. Basically, introducing a change in temperature suddenly unto this bacteria gives a stress and therefore affecting its growth rate. This shows that the environmental temperature in which the bacteria lives is very important for its survivability.

Bile Salts and Osmotic stress

Bile Salts, which are considered as an anti-bacterial barrier are secreted by all mammals. These anti-bacterial barriers have an innate immunity effect that definitely affect the growth rate of lactobacillus casei since these bacteria are mostly used or introduced as a probiotic inside the body. Osmotic stress is also observed when the bacteria is exposed to a large amount of salt. Osmotic is the spontaneous transfer of solvent molecules in a permeable membrane to balance the concentration on both sides. This means that the addition of salt can affect the cell property of the bacteria since different solvents can penetrate inside. Based from researches, the growth and expression patterns of lactobacillus casei changed when salt is introduced. Modifications in cell membrane were also found based from the research. Essentially, these stresses that the lactobacillus casei experience affects its growth rate.


The survivability of lactobacillus casei greatly depends on the different nutrients that it can synthesize as an energy source. The lack of an energy source definitely affects its growth rate. According to researches, starvation decreases the ability of the bacteria to accumulate its wanted nutrients which is needed for survivability. However, when starvation arises, these bacteria are able to adapt. The bacteria creates proteins in order to survive the stress.

Acid and Alkali Stress

The effect of pH and different acids found in the environment affects the growth of lactobacillus casei. The environmental conditions in the stomach are very acidic due to the gastric juices that it produces. This is dangerous for the bacteria and creates an extreme acid stress for the bacteria. According to researches, lactobacillus case tends to change its acid stress response as time passes by. The growth of these bacteria under extreme acidic conditions caused a lot of molecular and structural changes resulting into a sluggish growth.


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