## 5 Conclusions  
In this study, a PET-active bacterium _S. maltophilia_ PRS8 was isolated from plastic-contaminated soil that could depolymerize PET at a mesophilic temperature. The strain  
\begin{table}
\begin{tabular}{l l l l l l l} \hline \hline
**Enzyme** & **Strain** & **MW (kDa)** & **Sequence** & **Optimum** & **Optimum pH** & **Reference** \\ \hline Cutinase-like & PSR8 & 58 & Unknown & 40 & 8.0 & This work \\ Lipase (LipSM54) & GS11 & 52.8 & KX353755 & 35 & 8.0 & [38] \\ Lipase (LipSm) & Psi-1 & 40.7 & KCl014616 & 64.5 & 8.0–9.0 & [39] \\ Esterase (est7) & OUC\_Est10 & 76.6 & MH253883 & 45 & 9.0 & [41] \\ \hline \hline \end{tabular}
\end{table}
Table 7: Ester-active enzymes from _S. maltophilia_.  
PRS8 was observed to develop a biofilm on the PET surface that facilitated the bacterium in the process of PET degradation. The cutinase-like activity in the degradation medium demonstrated its role in the degradation of PET. The purified enzyme was stable to various environmental factors and efficiently hydrolyzed PET at a mesophilic temperature. Considering its degradation potential against a recalcitrant polymer, _S. maltophilia_ PRS8 and its enzymes could be potential candidates for further utilization against PET waste and the recovery of value-added products, considering bio-upcycling for the circular economy.  
The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app13063686/s1](https://www.mdpi.com/article/10.3390/app13063686/s1)]([https://www.mdpi.com/article/10.3390/app13063686/s1](https://www.mdpi.com/article/10.3390/app13063686/s1)), S1. UV PET treatment; S2. Experimental Design; Table S1. Placket Burman design of factors with specific enzyme activity (U/mg) as response. Table S2. ANNOVA for Placket-Burman Design; Table S3. Central Composite design of factors with specific activity (U/mg); Table S4. ANNOVA for Central Composite design; Figure S1. FT-IF spectra of PET flakes before and after UV exposure; Figure S2. Fourier-transform infrared spectra; Figure S3. DSF analysis of PET samples. Reference [48] is cited in the Supplementary Materials.  
Conceptualization, A.A.S., F.H., S.C. and J.A.L.-P.; methodology, S.U.D., K., S.M.S., S.U. and E.C.; software, A.A.S., S.U.D., K. and S.M.S.; validation, S.U.D., K., S.M.S., S.K., M.B. and A.O.B.; formal analysis, A.A.S., S.U.D., F.H., K., S.M.S., S.K., M.B., S.C., A.O.B., S.V.M., B.Z. and J.A.L.-P.; investigation, A.A.S., S.U.D., F.H., K., S.M.S., S.K., M.B., S.C. and A.O.B.; resources, A.A.S., F.H., S.K., S.C. and J.A.L.-P.; data curation, A.A.S. and J.A.L.-P.; writing--original draft preparation, S.U.D. and A.A.S.; writing--review and editing, all authors.; visualization, A.A.S., F.H., S.K. and M.B.; supervision, A.A.S. and J.A.L.-P.; project administration, A.A.S. and J.A.L.-P. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The files of the models presented in this study are available on request from corresponding author. The other data are available in the article.  
The authors thank the Higher Education Commission of Pakistan (HEC) for providing funds for the internships under the International Research Support Initiative Program (IRSIP), the government of Turkey for providing funds for this research, Burslari Research. The authors also thank the Royal Physiographic Society in Lund, Sweden, the Crafoord Foundation, the Swedish Research Council for Sustainable Development (Forms, no. 201-01107) and the Mistra Foundation (the \"STEPS\" project no. 2016/1489) for the research funding.  
The authors have no conflict of interest.