polyglutamic

Polyglutamic acid, commonly abbreviated PGA, refers to polymers formed from glutamic acid. The term encompasses two principal forms: α-polyglutamic acid, in which glutamate units are linked by standard α-peptide bonds, and poly-γ-glutamate (γ-PGA), in which the γ-carboxyl group of one residue links to the α-amino group of the next, creating γ-peptide bonds. γ-PGA occurs naturally as an extracellular polymer secreted by certain Bacillus species, most notably Bacillus subtilis var. natto, during the fermentation of soybeans. This γ-PGA is largely responsible for the sticky texture of natto.

Properties of PGA polymers include water solubility, biodegradability, and low toxicity. They can reach high molecular weights and are highly hydrophilic, forming highly viscous solutions and gels, particularly in the presence of certain metal cations. PGA is capable of absorbing large amounts of water, acting as a humectant, and it can form films and hydrogels suitable for various applications.

Production and sources typically involve microbial fermentation, with Bacillus strains synthesizing γ-PGA from glutamate substrates. Fermentation conditions influence the polymer’s molecular weight and physico-chemical characteristics.

Applications of PGA span several sectors. In the food industry, PGA serves as a thickener, texture enhancer, and humectant. In cosmetics, it is valued for moisturizing properties. In biomedicine, PGA-based hydrogels and biomaterials are explored for wound dressings, controlled drug delivery, and tissue engineering due to biocompatibility and biodegradability.

Safety and regulation: PGA, including γ-PGA derived from natto, is generally considered safe for use in foods and cosmetic formulations in many jurisdictions. See also natto, biodegradable polymers, and polypeptides.