Microbial production and chemical transformation of poly‐γ‐glutamate

Abstract

Poly-γ-glutamate (PGA), a novel polyamide material with industrial applications, possesses a nylon-like backbone, is structurally similar to polyacrylic acid, is biodegradable and is safe for human consumption. PGA is frequently found in the mucilage of natto, a Japanese traditional fermented food. To date, three different types of PGA, namely a homo polymer of d-glutamate (D-PGA), a homo polymer of l-glutamate (L-PGA), and a random copolymer consisting of d- and l-glutamate (DL-PGA), are known. This review will detail the occurrence and physiology of PGA. The proposed reaction mechanism of PGA synthesis including its localization and the structure of the involved enzyme, PGA synthetase, are described. The occurrence of multiple carboxyl residues in PGA likely plays a role in its relative unsuitability for the development of bio-nylon plastics and thus, establishment of an efficient PGA-reforming strategy is of great importance. Aside from the potential applications of PGA proposed to date, a new technique for chemical transformation of PGA is also discussed. Finally, some techniques for PGA and its derivatives in advanced material technology are presented.

Bacterial-derived biopolymers: Advanced natural nanomaterials for drug delivery and tissue engineering

“…MW is a crucial factor for drug delivery applications. PGA polymers larger than 3 kDa do not readily diffuse through capillary walls and glomerular endothelial cells [87,91]. Nevertheless, it is well-known that the tumor vasculature is often disordered and more permeable compared to normal state, a phenomenon which is called as the enhanced permeability and retention effect (EPR).…”

“…Therefore, the MW of PGA can be exploited as a selectivity factor for specific delivery of encapsulants to the tumor and not the normal tissues [87,91]. …”

Development of bio-based fine chemical production through synthetic bioengineering

“…γ-PGA is an unusual anionic polypeptide comprising D/L-glutamate monomers polymerized through γ-glutamyl bonds [83]. γ-PGA is produced by Bacillus strains from glutamate or glucose [84,85]. B. subtilis was engineered to increase γ-PGA production by overexpression of γ-PGA synthetase [86] or by deletion of γ-PGA-degrading enzymes [87].…”

Highly efficient rice straw utilization for poly-(γ-glutamic acid) production by Bacillus subtilis NX-2

“…Currently, glucose and citric acid are the dominant carbon sources used in the PGA production by fermentation (L and Van, 2001;Ashiuchi, 2013). However, these nutrients are mainly derived from food feedstocks such as corn, potato, and sugarcane, with their excessive consumption inevitably bringing about serious food shortages, causing many social dilemmas and criticisms.…”