activity of tannins
The presence of tannin protects plants from bacterial and fungal decay; it preserves vegetable tanned leathers from putrefying. It prevents the formation odor inside shoes.
Master craftsmen have been aware since ancient times of these qualities which, in recent times, have been confirmed by scientific research conducted by prestigious universities.
An “antibacterial” is defined as a substance capable of destroying bacteria or suppressing their growth. The antibacterial activity of a substance is determined by the quantity of bacteria that it is able to eliminate: it is considered significant if it is equal to or greater than 90%.
There is a clear explanation for all of this: tannin is a powerful natural antibacterial agent.
the tannin present in vegetable tanned leather can eliminate 99% of the bacteria with which it comes into contact.
Bacteria: One of the Earliest Known Life Forms
Bacteria are essentially single-celled microorganisms, invisible to the human eye, that live in almost every environment, from volcanoes to icebergs, and from the bottom of the sea to each city around the world.
Some are harmful to humans: tuberculosis, scarlet fever, salmonella and meningitis are the result of bacterial infections. But not all of them are our “enemies”: many bacteria are harmless, and others are even beneficial. For example, bacteria are responsible for some food transformation processes that make it possible to obtain yogurt from milk.
Humans and bacteria coexist in different symbiotic relationships. Bacteria live on the skin, in the genitourinary system and in the intestines: the so-called bacterial flora is responsible for intestinal physiologic processes and they work in synergy with our immune systems. These bacteria, along with other microorganisms, are also referred to under the collective term “microbiota”.
The Structure of Bacteria
Bacteria are covered by a bacterial cell wall that essentially acts like “a coat of armor”: it protects the bacterium from external attacks and regulates the exchange of nutrients and metabolites with the outside. The bacterial wall is made of a polymer, called “peptidoglycan”, which is composed of amino acids and sugars.
The peptidoglycan forms a layer outside the plasma membrane. Some bacteria also have a second membrane.
The cell walls can have two different types of structure. Based on their different structures, bacteria are subdivided into two broad class according to the different structure of their cell wall:
These microorganisms have an extremely simple structure: in fact, they only have one cell wall, composed of a thick layer of peptidoglycan.
They are characterized by a more complex structure: inner cell membrane, a peptidoglycan layer and, on top, another bacterial outer membrane, formed by a lipid bilayer.
Gram Stain Test
The Gram stain is a laboratory test developed by the Danish bacteriologist Hans Joachim Christian Gram to identify Gram-positive and Gram-negative bacteria. This method consists of subjecting microorganisms to a stain treatment. Depending on the different structure of the wall, they will appear under the microscope in different colors: Gram-positive purple, Gram-negative red.
Example: Staphylococcus aureus
Example: Escherichia coli
The Antibacterial Activity of Tannins
To eliminate bacteria, it is necessary to penetrate their “armor”, or the cell wall covering them. Tannin is able to pass through the cell wall up to the internal membrane and interferes with the metabolism of the cell, destroying it.
In Gram-positive bacteria, the action of tannin is rapid; in Gram-negative bacteria, which have a bilayered membrane, it is slower.
This is a fundamental distinction because certain types of bacteria thrive in some microbial ecosystems: for example, the bad odor inside of shoes is the result of a prevalence of Gram-positive bacteria.
If you wear shoes with a vegetable tanned leather lining or insole, the tannin present in the leather fiber or the leather will act selectively, destroying the bacteria responsible for the odor of the shoes and balancing the other bacterial populations.
A Different Approach to the Study of Bacteria
New biomedical technologies make it possible to study the behavior of microorganisms in their environment, providing new laboratory research initiatives.
This research has resulted in a new approach towards bacterial life. Up until a few decades ago, bacteria had a negative connotation and were automatically considered a possible threat to be eliminated.
An understandable and necessary approach in certain cases, like in operating rooms, but one that is unwarranted when it comes to daily “hygiene”.
In fact, the prolonged and excessive use of aggressive disinfecting substances could prove to be counterproductive for human health.
Therefore, it is important to find antibacterial solutions that are effective without disrupting the natural balances of human physiology and the bacterial ecosystem, while avoiding to cause resistance to certain species.
Have we Piqued your Interest?
For more in-depth information, go to the page “The Benefits of Tannin” where you will discover other properties that make tannin unique among its class and effective in a variety of contexts. For example, the tannin molecule has the capacity to bind to animal proteins and stabilize them, a property that makes it an excellent tanning agent.