Hydrolytic Degradation and Biodegradation of Hydrogel Prepared from Microbial Poly(.EPSILON.-lysine).

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Hydrolytic and enzymatic degradation processes of hydrogels prepared by γ-irradiation from microbial poly (e-lysine) (PL) were studied. Hydrolysis studies on PL hydrogels were carried out in deionized water at 40, 75, and 95°C. PL hydrogel, which was prepared with 100 kGy γ-irradiation dose and 5 wt% PL concentration. was degraded by only 2% at 40°C for 17 hours, and degraded by 14% at 75°C for 13.5 hours. As the heating temperature was increased, the degradation rate was increased. The specific water content (wt. of absorbed water/wt. of dry gel) was increased with the progress of hydrolytic degradation, The rate of hydrolytic degradation of heterogeneous opaque PL hydrogel (≤ 3 wt% PL concentration) was slower than that of homogeneous transparent PL hydrogel. The thermal stability of PL hydrogel was found to be dependent on the structure of the gel. The enzymatic degradations of PL hydrogels were studied at 40°C and pH 7.0 in the 25 mM phosphate buffer with Protease A produced from Aspergillus oryzae. PL hydrogels were degraded by 20-60% for 17 hours by Protease A. The rate of enzymatic degradation of PL hydrogel was much faster than the rate of simple hydrolytic degradation. The enzymatic degradation occurred at the surface of the PL hydrogel. The surface erosion by Protease A was confirmed by monitoring the time-dependent changes in the specific water content of the PL hydrogel.