How is lactic acid produced?

The Swedish chemist, Carl Wilhelm Scheele, was the first to extract lactic acid from milk. However, despite its name, lactic acid is also present in certain fruits and vegetables, in wine, and even in the skin, as it is part of the Natural Moisturizing Factor (NMF).

Note: The NMF or Natural Moisturizing Factor accounts for 30% of the total dry weight of the stratum corneum. It is composed of amino acids, their derivatives, and extracellular compounds such as lactic acid or urea. Its hygroscopic properties allow it to capture and retain water in the stratum corneum, thus maintaining good skin hydration.

Lactic acid offers many benefits for the skin. In cosmetics, it is a widely used active ingredient due to its keratolytic, moisturizing, and depigmenting properties. It is highly valued because, unlike glycolic acid, it has a gentle exfoliating power. Therefore, lactic acid is suitable for all skin types, even the most sensitive ones.

In most cases, lactic acid is obtained through a natural process. Indeed, this process results from the fermentation of various carbohydrates such as corn, sugar, or even the lactose found in milk with the help of microorganisms. Depending on the strain used, we can obtain either the L(+) form of lactic acid or the D(-) form of lactic acid. However, the L(+) form is the biologically active form of lactic acid found in the NMF. The L(+) form of lactic acid is obtained, among other things, by microorganisms of the Lactobacillus genus.

There are also synthetic methods for obtaining lactic acid, such as the degradation of sugars or the oxidation of propylene glycol. However, the resulting product is an inactive racemic mixture of the two enantiomers L(+) and D(-) of lactic acid.

Take note : in chemistry, some molecules can exist in two different configurations, this is referred to as enantiomerism. We distinguish between levorotatory (L) and dextrorotatory (D) compounds based on their rotational power. Some molecules are active only in one of the two forms.