What you need to know about polyglutamic acid.

The polyglutamic acid is a biopolymer derived from the amino acid glutamic acid. This compound was first isolated from the marine jellyfish. It enables the organism to retain water in its tissue and prevents rapid dehydration caused by ocean salt. Polyglutamic acid occurs in the mucilage of natto, a traditional Japanese food with a sticky, paste-like texture obtained by fermenting soybeans. It served to accelerate wound healing, the polyglutamic acid is now known for its hydrating properties. It is listed under the INCI name "Polyglutamic Acid". In a skincare formulation, the polyglutamic acid is typically used at concentrations between 0.1 and 3%.

Polyglutamic acid is a biotechnological molecule produced exclusively through microbial fermentation.

Its production relies on the activity of certain Gram-positive bacteria of the class Bacilli, present in soil or on plant surfaces. Among the species used most in this process are Bacillus subtilis and Bacillus licheniformis. This fermentation technology enables polyglutamic acid to be produced at large scale under sustainable conditions that respect the environment and with a high degree of purity. One particular aspect of the production of polyglutamic acid is that it does not occur via a ribosomal pathway. Unlike most peptides, which ribosomes produce by reading messenger RNA to assemble amino acids, polyglutamic acid is formed via a non-ribosomal mechanism. This synthesis involves specialised enzymes able to assemble amino acids directly into a long polymeric chain. Non-ribosomal production occurs only in certain microorganisms, such as bacteria and fungi.

Serums, face masks, targeted eye-contour treatments: polyglutamic acid is a versatile active ingredient in various skin care products. This popularity stems from the distinct benefits of polyglutamic acid for the skin.

• Polyglutamic acid is recognised for its hydrating properties.

  Polyglutamic acid is primarily used as a hydrating agent in skin care. It can form a microgel—a film on the skin surface that swells and traps water molecules, enhancing retention in the epidermal tissues. Polyglutamic acid can thus bind up to 5,000 times its weight in water. Moreover, studies have shown it stimulates the production of lactic acid, urocanic acid, and pyrrolidone carboxylic acid—components of the natural moisturising factor. Located in the stratum corneum, these hygroscopic compounds help maintain skin hydration. Finally, polyglutamic acid reduces the synthesis of hyaluronidase, the enzyme that degrades dermal hyaluronic acid.

The various actions of polyglutamic acid make it an ally for dehydrated skin.

• Polyglutamic acid may help reduce signs of ageing.

  In addition to its hydrating properties, which help prevent and reduce dehydration-related fine lines, polyglutamic acid may have a broader effect on skin laxity. Indeed, a study in vitro showed that this active could increase the expression of the genes col1a1a and col1a1b, associated with collagen production, and the genes eln1 and eln2, linked to elastin synthesis. As a reminder, collagen and elastin are support proteins of the dermal extracellular matrix that play a key role in skin suppleness and elasticity. These initial results, although interesting, must be confirmed in clinical studies before concluding that polyglutamic acid affects skin ageing.

• Polyglutamic acid has wound-healing properties.

  Polyglutamic acid supports wound healing and cellular regeneration. It stimulates local production of the growth factor TGF-β and β-catenin, two molecules involved in cell proliferation, collagen synthesis, and angiogenesis. Polyglutamic acid may help accelerate healing of minor wounds or promote the rapid resolution of post-acne marks (post-inflammatory hyperpigmentation and post-inflammatory erythema). It would be useful to conduct studies to confirm this hypothesis in the coming years.

• Polyglutamic acid could soothe redness and itching.

  Polyglutamic acid may help soothe sensitive skin and reduce redness and itching associated with inflammatory processes. Preclinical studies have shown that this compound can reduce the expression of vascular endothelial growth factor A (VEGF-A) and its receptor VEGFR2, key molecules in angiogenesis linked to chronic inflammation. By lowering these mediators, polyglutamic acid helps limit excessive blood vessel proliferation and vascular permeability. Clinical trials are required to confirm this, but polyglutamic acid could attenuate redness and swelling seen in inflammatory conditions.

Even if it is less common, the polyglutamic acid can be used for hair care. Its various properties, outlined above, apply to the scalp, which needs regular hydration and periodic soothing to stay healthy. As for hair lengths, there are reasons to believe this ingredient could be beneficial. Exposed daily to mechanical, thermal, and chemical stress, strands may lose shine and weaken, forming split ends beyond repair. Thanks to its film-forming properties, polyglutamic acid creates a protective layer that complements the hydrolipidic film on the hair surface. This action could help limit the hair porosity, better protect the fibre against external factors and ultimately to maintain supple and resilient hair.

Clinical studies, which do not yet exist, are required to validate the benefits of polyglutamic acid for hair.

Polyglutamic acid demonstrates high skin tolerability.

This ingredient is not known to irritate or sensitise the skin and is not linked to inflammatory reactions. Its high tolerance is due in part to its high molecular weight and polymeric structure, which limit penetration into the skin. The safety of polyglutamic acid has been assessed in several studies, in particular patch tests on volunteers applying the ingredient under occlusion for 24 to 48 hours. The results showed no reaction: no erythema, oedema or pruritus were observed. Analyses in vitro have demonstrated the absence of genotoxicity, meaning that polyglutamic acid does not cause mutations or DNA alterations. It is suitable for daily use and no contraindication prevents its use during pregnancy or breastfeeding.

• SONA H.-J. & al. In vitro evaluation of new functional properties of poly-γ-glutamic acid produced by Bacillus subtilis. Saudi Journal of Biological Sciences (2014).

• RADECKA I. & al. Poly-γ-glutamic acid: production, properties and applications. Microbiology Society (2015).

• SUNG M.-H. & al. Promotion effects of ultra-high molecular weight poly-γ-glutamic acid on wound healing. Journal of Microbiology and Biotechnology (2015).

• NAJAR N. & al. Poly-glutamic acid (PGA) - Structure, synthesis, genomic organization and its application: a review. International Journal of Pharmaceutical Sciences and Research (2015).

• HIURA N. & al. Characterization of poly(L-glutamic acid)-grafted hyaluronan as a novel candidate medicine and biomedical device for intra-articular injection. Journal of Biomedical Materials Research (2017).

• 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).