Lactic acid bacteria (LAB) is a general term for bacteria that can produce a large amount of lactic acid using fermentable carbohydrates. They are widely found in nature, especially in the intestines, mouths, vaginas and other parts of humans and animals, as well as in plant surfaces, dairy products, fermented foods and other environments.
The metabolic principles of lactic acid bacteria mainly include the following aspects:
Metabolic mode: Lactic acid bacteria convert sugars into lactic acid through fermentation.
This process not only gives fermented foods a unique flavor and taste, but also inhibits the growth of other harmful microorganisms and plays a certain role in preserving freshness.
Antibacterial mechanism: Organic acids (such as lactic acid) produced by lactic acid bacteria metabolism exist in two states in the extracellular fluid: dissociated and undissociated.
Undissociated organic acid molecules can enter the cell by free diffusion. Due to the alkaline environment in the cell, the organic acid dissociation equilibrium moves toward the direction of producing hydrogen ions and acid radical ions, thereby producing hydrogen ions and acid radical ions.
These ions cannot diffuse out of the cell by free diffusion, so bacteria need to consume energy to transport hydrogen ions out of the cell through active transport to maintain the stability of the intracellular environment. In addition, organic acids can also compete with nutrients in microorganisms, further inhibiting the growth of harmful microorganisms.