Team:Osaka/Project pga

Gamma polyglutamic acid

OVERVIEW

Gamma polyglutamic acid (γ-PGA) is a very interesting biopolymer that attracts attention in late years.
It can be found in "natto", a Japanese traditional food , fermented soybeans. This healty food is very sticky.

In this sticky product secreted by Bacillus subtilis, γ-PGA is contained.γ-PGA and its derivatives offer a wide range of unique applications including being used as thickener, humectant, drug carrier, biodegradable fibers, highly water absorbable hydrogels, biopolymer flocculants, and heavy metal absorber. (Ing-Lung Shih et al,. 2001→)
Most famous products of PGA is highly water absorbable hydrogels. Its PGA is from B.natto. PGA fromB.natto have high ability to absorb and hold water. This character is strengthened by UV-crosslink among PGA chains and very useful to environmental problems.
Further more, PGA is very safe, not having toxicity to animals.

PGA STRUCTURE

(Ing-Lung Shih et al,. 2001→)

It is Dehydration-condensation reaction between gamma-position carboxyl group and alpha-position amino group of glutamate to compose PGA.
Glutamate have chirality. Although almost glutamate exist in L-form, PGA don't have only L-form Glutamate but also D-form Glutamate.
The ratio with L and D depends on some factors, species, culture condition and so on. These factors effect on the degree of polymerization.

Poly glutamate synthetase

Poly glutamate synthetase(PGS) is necessary to produce PGA in Escherichia coli. PGS gene includes three ORF (open reading flame),which are pgsB, pgsC, and pgsA. These ORFs code three essential enzymes to create PGA.

PGA contains both D and L glutamate.

To increase the amount of PGA production, co-expression of glutamate racemase and PGS is needed.

PGS is originally localized in cell membrane, and proposed to produce PGA from D,L-Glutamic acid. Bacillus subtilis has enzymes to biodegrade PGA; however, E. coli does not. Therefore, we want E. coli to produce PGA for greening of the desert.