Poly-gamma-glutamic acid (gamma-PGA) is a very promising biodegradable polymer that is produced by Bacillus subtilis. Gamma-PGA is water-soluble, anionic, biodegradable, and edible. This paper reviews the production of a strain of gamma-PGA and recent developments with respect to applications in terms of Ca absorption, moisturizing properties, gamma-PGA conjugation, super absorbent polymer, and so on. Our recent research shows that gamma-PGA can be used as an immune-stimulating and anti-tumor agent, especially at high molecular weight.
An enzymatic system for poly g-glutamate (PGA) synthesis in Bacillus subtilis, the PgsBCA system, was investigated. The gene-disruption experiment showed that the enzymatic system was the sole machinery of PGA synthesis in B. subtilis. We succeeded in achieving the enzymatic synthesis of elongated PGAs with the cell membrane of the Escherichia coli clone producing PgsBCA in the presence of ATP and D-glutamate. The enzyme preparation solubilized from the membrane with 8 mM Chaps catalyzed ADPforming ATP hydrolysis only in the presence of glutamate; the D-enantiomer was the best cosubstrate, followed by the L-enantiomer. Each component of the system, PgsB, PgsC, and PgsA, was translated in vitro and the glutamatedependent ATPase reaction was kinetically analyzed. The PGA synthetase complex, PgsBCA, was suggested to be an atypical amide ligase.
A bacterium with high poly-gamma-glutamate (PGA) productivity was isolated from the traditional Korean seasoning, Chung-Kook-Jang. This bacterium could be classified as a Bacillus subtilis, but sporulation in culture was infrequent in the absence of Mn2+. It was judged to be a variety of B. subtilis and designated B. subtilis (chungkookjang). L-Glutamate significantly induced PGA production, and highly elongated PGAs were synthesized. The volumetric yield reached 13.5 mg ml(-1) in the presence of 2% L-glutamate. The D-glutamate content was over 50% in every PGA produced under the conditions used. During PGA production, glutamate racemase activity was found in the cells, suggesting that the enzyme is involved in the D-glutamate supply. Molecular sizes of PGAs were changed by the salt concentration in the medium; PGAs with comparatively low molecular masses were produced in culture media containing high concentrations of NaCl. B. subtilis (chungkookjang) harbors no plasmid and is the first B. subtilis strain reported with both naturally high PGA productivity and high genetic competence.
Introduction
Historical Outline
Chemical Analysis
Chemical Synthesis
Molecular Structure
Molecular Spring
Chemical Modification
Esterification
Crosslinking
Producers
Glutamic Acid‐dependent Producers
Glutamic Acid‐independent Producers
Physiology
Nullification of Immunity in Infectious
B. anthracis
Neutralization of Near‐cell Surface in Alkalophiles
Prevention of Drastic Dehydration under High‐saline Conditions in Halophiles
Regulation of Osmotic Pressure in Cnidarians
Molecular Genetics
Encapsulation (
cap
) Genes
Poly‐γ‐glutamic Acid Synthesis (
pgs
) Genes
Regulatory Genes
Biosynthesis
Poly‐γ‐glutamic Acid Precursor Biosynthesis
Poly‐γ‐glutamic Acid Biosynthesis
Biodegradation
Occurrence
Enzymology
Molecular Genetics
Applications
Potential Applications
Biodegradable Plastics and Hydrogels
Bioremediation
Other Applications
Manufacturers
Outlook and Perspectives
Patents
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