PROPERTIES OF HYDROGELS PREPARED BY GAMMA-IRRADIATION IN MICROBIAL POLY(GAMMA-GLUTAMIC ACID) AQUEOUS-SOLUTIONS

Poly(gamma-glutamic acid) (PGA) hydrogels have been prepared by means of gamma-irradiation of PGA produced by Bacillus subtilis IFO3335 in aqueous solutions. When a dosage of gamma-irradiation was 2 Mrad or more and a concentration of PGA in water was 2 wt% or more, transparent hydrogels could be produced. In the case of 2 Mrad of gamma-irradiation and 5 wt% of PGA concentration, specific water content (wt of water/wt of polymer) of PGA hydrogel was approximately 3500. Specific water contents of PGA hydrogels decreased markedly with an increase in a dosage of gamma-irradiation. Swelling equilibria of PGA hydrogels were measured in water or in aqueous solutions of various pH's or concentrations of NaCl or CaCl2. Under acid conditions or on addition of electrolytes, degrees of swelling of PGA hydrogels were smaller than that in distilled water.