Polyglutamic acid is a relatively recent active ingredient in skincare, extracted from the mucilage found in fermented soybeans. An increasing number of scientific studies are documenting its moisturising power on the epidermis as well as its ability to soothe irritations and burns. What is its biological mode of action to maintain hydrated skin? Discover it here.
Polyglutamic acid for hydrated skin?
Summary
Published on June 2, 2025, by Maylis, Chemical Engineer — 6 min of reading
Themes:
Polyglutamic acid, the key to more hydrated skin?
The polyglutamic acid is a biopolymer derived from the polymerisation of glutamic acid. It is the main component of nattō, a Japanese dish made with fermented soybeans. Traditionally, the polyglutamic acid was used in medicine to accelerate the healing of wounds and burns. Today, it is primarily recognised for its nutritional contributions but also has several interesting cosmetic properties, starting with its hydrating potential.
The moisturising properties of polyglutamic acid have been widely demonstrated, including in a clinical study, that is, conducted with human volunteers. This study was carried out with five panellists initially placed for fifteen minutes in a room with controlled temperature and humidity (temperature = 22°C and humidity = 60%). Two formulations were then applied to each of their arms: one contained 0.2% polyglutamic acid and the other contained 5% glycerol, a moisturiser often used in skincare. The hydration before and two hours after was measured by corneometry. The results are presented in the table below and show the moisturising effects of polyglutamic acid, superior to those of glycerol.
| Formula tested | Alteration in Hydration |
|---|---|
| 5% glycerol | + 7.5% |
| 0.2% Polyglutamic Acid | + 13.5% |
Alteration in the skin hydration of participants two hours after application of a cream containing polyglutamic acid or glycerol.
Source: YANG S.-A. et al. Gamma polyglutamic acid (gamma-pga, h form), gamma-polyglutamate hydrogels for use as superior hydrating agents in skincare and personal care products (2019).
How does polyglutamic acid affect skin hydration?
The polyglutamic acid is a biopolymer that combats skin dehydration at various levels:
Polyglutamic acid is a film-forming agent.
Polyglutamic acid is capable of forming a very thin film on the surface of the epidermal tissue. This molecular arrangement is referred to as a microgel. This microgel swells upon contact with water and traps H2O molecules. Thus, not only does polyglutamic acid limit transepidermal water loss, but it also promotes its retention through a humectant process. Indeed, polyglutamic acid is capable of retaining up to 5,000 times its weight in water. In comparison, hyaluronic acid retains up to 1,000 times its weight in water.
Polyglutamic acid stimulates the production of substances that make up the natural moisturising factor (NMF).
The natural moisturising factor is a set of hygroscopic molecules (amino acids, urea...) that form during the process of epidermal differentiation and retain water in the skin's superficial layer. Studies have shown that polyglutamic acid can boost the production of some of these molecules, including pyrrolidone carboxylic acid (PCA), lactic acid, and urocanic acid. In doing so, polyglutamic acid increases the water content of the stratum corneum, thus contributing to achieving a more hydrated and softer skin.
Polyglutamic acid restricts the activity of hyaluronidase.
Hyaluronidase is the enzyme responsible for the breakdown of hyaluronic acid. To clarify, hyaluronic acid is a molecule predominantly produced by the dermal fibroblasts that gives the skin its plump and filled-out appearance. The hyaluronic acid acts like a molecular sponge, capturing water. However, over the years, its content decreases: by the age of 50, the hyaluronic acid reserve has halved. This drastic drop impacts skin hydration and is partly responsible for the appearance of wrinkles and fine lines on its surface. By inhibiting the activity of the hyaluronidase enzyme, polyglutamic acid therefore prevents skin dehydration and the emergence of age-related signs.
Note: While polyglutamic acid aids in maximising the skin's hydration, its high molecular weight prevents it from acting deeply. Its action is limited to the skin's superficial layers. For complete hydration, it may be wise to pair it with low molecular weight hyaluronic acid, an active ingredient capable of penetrating deeper into the skin.
Sources
HONG-JOO SONA & al. In vitro evaluation of new functional properties of poly-γ-glutamic acid produced by Bacillus subtilis. Saudi Journal of Biological Sciences (2014).
MOON-HEE SUNG & al. Promotion effects of ultra-high molecular weight poly-γ-glutamic acid on wound healing. Journal of Microbiology and Biotechnology (2015).
RADECKA I. & al.Poly-γ-glutamic acid: production, properties and applications. Microbiology Society (2015).
YANG S.-A. & al. Gamma polyglutamic acid (gamma-pga, h form), gamma-polyglutamate hydrogels for use as super moisturizers in cosmetic and personal care products (2019).
