Development of Antimicrobial Thermoplastic Material from Archaeal Poly-γ-l-Glutamate and Its Nanofabrication

Abstract

Here we describe a stoichiometric ion-complex of archaeal poly-γ-L-glutamate (L-PGA) and hexadecylpyridinium cation (HDP(+)), called PGAIC, which shows remarkable chemical resistance and potential as a novel functional thermoplastic. PGAIC films suppressed the proliferation of prokaryotic (Escherichia coli, Bacillus subtilis, Salmonella typhimurium, and Staphylococcus aureus) and eukaryotic (Saccharomyces cerevisiae) microorganisms. Moreover, its antifungal activity was demonstrated against a prevalent species of Candida (Candida albicans) and a filamentous fungus (Aspergillus niger). The minimal inhibitory concentrations were estimated as 0.25 mg mL(-1), and zones of growth inhibition appeared when PGAIC-coated polyethylene terephthalate (PET) films were placed in culture plates, whereas PET had very little effect on fungal growth. Soluble PGAIC thus shows promises as an antimicrobial and as a coating substrate. We also succeeded in synthesizing an L-PGA-based nanofiber using an ethanol solution of PGAIC.

Microbial production and chemical transformation of poly‐γ‐glutamate

“…Although PGAIC is an ionic complex, it was unexpectedly stable to chemicals such as salts, acids and alkalis, suggesting the involvement of a driving force in the solidification of PGAIC other than a typical ionic interaction. It is noteworthy that PGAIC exhibits good solubility in alcohols (Ashiuchi et al ., 2013a), whereas PGA itself never dissolves in alcohols. These transformable properties must be taken into account when processing PGA for diverse applications.…”

“…Ashiuchi and colleagues (2013a) recently demonstrated that a compound used in toothpaste, called hexadecylpyridinium cation (HDP + ), serves as a potent candidate to suppress the extreme hydrophilicity of PGA. In fact, a water-insoluble complex was readily formed by mixing PGA and HDP + at 60°C for 30 min.…”

Antimicrobial peptides and proteins in the face of extremes: Lessons from archaeocins

“…In the archaeal domain, toxin-antitoxin system genes have been identified in Thermoplasmatales, several methanotrophs, and in the symbiotic archaeon, Nanoarchaeum equitans [64,65]. One study also mentions the use of a stoichiometric ion-complex of archaeal poly-g-Lglutamate and hexadecylpyridinium cation, called PGAIC, which showed antimicrobial activity against several bacterial and eukaryotic microorganisms, and was suggested for use as an antimicrobial coating agent [66].…”

A New Method to Purify Poly-γ-glutamic Acid Using Gemini Quaternary Ammonium Salts and Characterization of its Ionic Complex

“…Hexadecylpyridinium chloride (HDP) that includes a quaternary ammonium cation (Figure 1) is known as a disinfectant (Johansen et al, 2006). Quaternary ammonium cation binds to the carboxylic acid group of γ-PGA via an ionic bond, and water-insoluble and antimicrobial complexes are thus formed (Ashiuchi et al, 2013;Ashiuchi et al, 2015). Therefore, we hypothesized that it is possible to purify γ-PGA from the culture broth using the water-insoluble complex.…”