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

Abstract

Poly-gamma-glutamic acid (γ-PGA) is a water-soluble, nontoxic biodegradable polymer. It is extensively utilized in medicines, foodstu s, and cosmetics, as well as in water treatment. Highly pure γ-PGA is required for various purposes. In many cases, γ-PGA is produced by microbes of Bacillus sp. However, an increase in the viscosity of the culture broth is one of the major problems of γ-PGA production, as higher viscosity makes the separation and puri cation steps di cult. Herein, we propose a novel method to obtain pure γ-PGA using gemini quaternary ammonium salts (GQASs). The quaternary ammonium cation of GQASs binds to the carboxylic acid group of γ-PGA via an ionic bond, following which waterinsoluble and antimicrobial complexes are formed. These complexes are obtained in the aqueous solution, which were resolved in ethanol solution. With an increase in the added amount of GQAS, the negative charge of the complex decreased in the aqueous solution. Subsequently, the GQAS within the complexes was dissociated by the addition of NaCl, a ording pure γ-PGA in a high yield. Moreover, the complexes were shown to have antibacterial activity and adhered to glass, indicating that the complex itself has a utility value.

Knockout of pgdS and ggt gene changes poly-γ-glutamic acid production in Bacillus licheniformis RK14-46

“…Bacterial strains and plasmids, and primers used in this study are listed in Table 1 and Table S1, respectively. The B. licheniformis RK14-46 strain, γ-PGA hyper-producing mutant strain of RK14, was used throughout this study (Liu et al 2017;Liu et al 2018).…”