*3.6. Time-Dependent Analysis of PHB Degradation*

Finally, the time-dependent degradation rate of non-plasticized PHB film, PHB film including 10% tributyl citrate, and PHB film including 20% tributyl citrate was compared (Figure 6). These films are degraded by *Microbulbifer* sp. SOL66 for 1, 2, and 3 days were recovered and analyzed. After 3 days, the final degree of degradation was similar to more than 90%. However, non-plasticized PHB film was degraded by about 70% after 1 day of degradation and was almost completely degraded as the degree of degradation increased gradually, whereas the plasticized PHB films showed a very high degree of degradation of more than 80% even after one day of degradation. It suggests that tributyl citrate not only changes physical properties and increases the elongation properties of the PHB film, but is also very excellent in terms of biodegradability by *Microbulbifer* sp. SOL66.

**Figure 6.** Time-dependent analysis of PHB biodegradation by *Microbulbifer* sp. SOL66. Comparison of the degradation rate of non-plasticized PHB film, and tributyl citrate plasticized PHB films.
