**4. Conclusions**

Interest in biodegradable bioplastics has increased significantly as a way to reduce environmental pollution caused by non-degradable conventional plastics. However, unlike PBAT, which stretches well, PHB is brittle and is easily broken when a force is applied. In the case of PHB, its main advantage is its eco-friendly production process, as it can be produced and degraded by microorganisms. To overcome its property-related shortcomings, various types of plasticizers can be added to PHB.

Our study concluded that in the presence of plasticizer tributyl citrate, the degree of degradation was excellent compared to other plasticizers, and the robustness of the degradation rate was excellent even when the concentration of the plasticizer was increased. In addition, this suggests that there is a speedy screening process of plasticizers for PHB using *Microbulbifer* sp. SOL66, which has superior PHB degradation ability. Tributyl citrate plasticizer can be used to prepare bioplastic to have better qualities with a higher biodegradation rate, which can help to manage emerging plastic-related issues.

**Author Contributions:** J.Y.C., J.A., J.-M.J., J.-J.Y. and Y.-H.Y. conceived and designed the study; J.Y.C., S.H.K., H.J.J., D.H.C. and B.C.K. performed the experiments and drafted the manuscript; J.Y.C. and Y.-H.Y. interpreted the experimental results; J.Y.C., S.K.B., J.L. and Y.-H.Y. revised the manuscript. All authors have read and agreed to the published version of the manuscript.

**Funding:** This study was supported by the Research Program to solve social issues with the National Research Foundation of Korea (NRF), funded by the Ministry of Science and ICT [grant number 2017M3A9E4077234], National Research Foundation of Korea (NRF) [grant numbers NRF-2022R1A2C2003138 and NRF-2019M3E6A1103979]. This study was also supported by the R&D Program of MOTIE/KEIT [grant number 20009508 and 20018072].

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**

