5 UNICELLULAR ORGANISMS THAT ARE USED TO MAKE FOOD - BIOLOGY - 2025

There is a wide variety of single-celled organisms that are used to make food. Since ancient times, man has used microorganisms to make bread, wine, yogurt and cheese. Today the product range has been expanded to include sauerkraut, soy sauce, beer and miso.

Fungi and bacteria are the single-celled organisms that are usually used in the manufacture of these products. These living beings act on different foods, generally raw, creating colonies.

Saccharomyces cerevisiae. Source: A doubt, from Wikimedia Commons

In the vast majority of cases, these groups of microorganisms act by fermenting the sugars. Fermentation can be alcoholic, as occurs in bread, a product of the activity of the yeast fungus.

Other unicellular organisms produce a milk fermentation, used to make yogurt. In some wines, bacteria are used that produce a malolactic type fermentation.

On other occasions, these species act by breaking down the structure of the food, adding specific flavors, textures and aromas. At the same time, they prevent the proliferation of other colonies that could accelerate the natural decomposition process of food.

Examples of single-celled organisms used to make food

Saccharomyces cerevisiae

By Rainis Venta, from Wikimedia Commons

Brewer's yeast, as this species is known, is a single-celled fungus that since ancient times has been associated with the well-being and progress of humanity. It is a yeast of the heterotrophic type, which obtains its energy from glucose molecules.

It has a high fermentation capacity. This process occurs when Saccharomyces cerevisiae is in a medium rich in sugar, such as D-glucose. As a product of this, ethanol and carbon dioxide are generated.

If the conditions of the environment where the yeast is found lack nutrients, the body uses metabolic pathways other than fermentation that allow it to have energy.

This yeast is one of the species categorized as a GRAS microorganism, since it is considered a substance that can be safely added to food. It has several uses at an industrial level, being used mainly in the preparation of bread. It is also used in the production of wines and beers.

The carbon dioxide produced during fermentation is the gas that "sponges" the bread. Also, brewer's yeast is used in other similar foods, such as in pizza dough.

Lactobacillus delbrueckii subsp. bulgaricus

This gram-positive bacteria is elongated and filamentous in shape. It does not form spores and lacks mobility. Their diet is lactose-based. It is considered acidophilic, because it requires a low pH, between 5.4 and 4.6, to develop effectively.

It has the characteristic of being facultatively anaerobic. It is a species that has a fermentative metabolism, having lactic acid as its main product. This is used for the preservation of milk, which makes this bacterium widely used in the production of yogurt.

In the production of this dairy derivative, Lactobacillus delbrueckii subsp. bulgaricus is commonly used in conjunction with Streptococcus thermophilus. Both work synergistically with L. d. Bulgaricus, which produces amino acids from the proteins in milk. These give the yogurt its characteristic smell.

Initially, S. thermophilus begins to ferment lactose, generating an accumulation of acids. At this time, L bulgaricus, which is tolerant to acidic media, continues to act.

Both species of bacteria produce lactic acid, which causes a change in the structure of milk, giving yogurt its thick texture and characteristic flavor.

Lactobacillus plantarum

Lactobacillus plantarum. Taken and edited from theprobioticslab.com

It is a bacterium belonging to the Lactobacillaceae family, with the ability to carry out lactic-type fermentation. It can be found naturally in food or it can be added in order to preserve it.

Lactobacillus plantarum is one of the main responsible for the fermentation process of sauerkraut, a culinary preparation of Central European origin. It is very common in France, Germany, Switzerland, Russia, and Poland. Currently its consumption has spread to Asia and America.

The production of sauerkraut is based on the lactic fermentation of cabbage leaves (Brassica oleracea). The juices from the vegetables, together with the sea salt that is added to the preparation, form a natural brine.

Fermentation is achieved by the action of Lactobacillus plantarum, which anaerobically metabolize the sugars contained in cabbage. As a product of this process is lactic acid, which enhances the flavor and acts as a natural preservative.

Propionibacterium freudenreichii

This bacterium is used in the production of Emmental cheese. It is also used when Jarlsberg, Maasdam and Leerdammer cheeses are produced industrially. The concentration of this gram-positive bacteria is higher in Swiss-type dairy than in other cheeses.

In the manufacture of Emmental cheese, P. freudenreichii ferments lactate, thus forming acetate, carbon dioxide, and propionate. These products contribute the nutty and sweet flavor typical of this class of cheese.

Carbon dioxide is responsible for the "holes" that characterize them. Cheese makers can control the size of these holes by modifying temperature, curing time, and acidity.

Recent research maintains that the consumption of products containing this bacteria is beneficial for the body. They could contribute to the proper functioning of the intestinal tract and decrease the appearance of new cases of colon cancer.

Oenococcus oeni

It is an immobile, gram-positive bacterium that forms chains of ovoid cells. It belongs to the group of lactic bacteria. It obtains its energy through respiration, in the presence of oxygen, and in its absence they take it from fermentation.

It is the main lactic acid type bacteria that intervenes in the malolactic fermentation of wine. This type of fermentation is a simple metabolic process, since it has only one reaction. Malic acid, by the catalytic action of the malolactic enzyme, is transformed into lactic acid.

Another by-product is carbon dioxide, due to its decarboxylation. CO2 is not as evident as that produced in those cases of alcoholic fermentation.

Occasionally in the elaboration of wines the action of several bacteria, apart from O. oeni, could be combined. Saccharomyces cerevisiae and Kloeckera apiculata could be used to enhance the characteristics of this drink .

References

1. Wikipedia (2019). Lactobacillus delbrueckii subsp. Bulgaricus. Recovered from en.wikipedia.org.
2. Microbiology online (2019). Producers. Recovered from microbiologyonline.org.
3. Wikipedia (2019). List of microorganisms used in food and beverage preparation. Recovered from en.wikipedia.org.
4. OMICS International (2019). Uses of Microorganisms in Food. 2nd International Conference on Food Microbiology- Madrid, Spain. Recovered from omicsonline.org.
5. Ayushi R. (2019). Microbes in the Food Industry - Microorganisms - Biology Recovered from biologydiscussion.com.