γ-Poly glutamic acid (γ-PGA) is a novel molecule that is a component of the mucilage of the fermented soybean food product commonly found in Japan called natto. The International Nomenclature Cosmetic Ingredient (INCI) name of γ-PGA is natto gum and it is classified as a film-forming agent. The sodium salt of γ-PGA, which is more commonly used and thus served as the test sample in this paper, displays the visual appearance of a sticky paste.
The fermented soybean mucilage consists of a mixture of γ-PGA and fructan produced by Bacillus natto. Further research by Bovarnick revealed γ-PGA to be a fermentation byproduct freely secreted into growth medium outside of the cell walls of Bacillus subtilis. This discovery advanced collateral investigations to determine whether this bacteriological process could be reproduced in other species of Bacillus.
Characteristics of γ-PGA
Recent work by Lung and Da-Yeh further illustrates the applications and production of γ-PGA from microorganisms by gamma irradiating to promote chemical cross-linking between monomeric units to form a γ-PGA hydrogel. The finished gel was lyophilized to assure its physical chemical stability.
The lyophilized product was characterized by Lung and Da-yeh by nuclear magnetic resonance (C13 and H1), Fourier Transform Infrared Spectroscopy and thermal gravimetric analysis in its protonated form, as well as the salts of Na+, K+, NH4+, Ca2+ and Mg2+.