Tracking Degradability of PBSu with Size-Exclusion Chromatography

Researchers from Gunmo University (Gunmo, Japan) developing marine-degradable poly(butylene succinates) (PBSus), a biodegradable plastic that breaks down into carbon dioxide and water (1), examined the influence of the molecular weight of specific samples on their biodegradability. The team examined the influence of the molecular weight of specific samples on biodegradability. Samples with differently molecular weighted samples were prepared by fractionation with the use of preparative size-exclusion chromatography (SEC), and biochemical oxygen demand (BOD) in seawater was then evaluated. A paper based on the team’s efforts was published in Chemosphere (2).

Plastic waste pollution has become a serious challenge as amounts of the product ending up into oceans has been increasing every year (3). Biodegradable polymers, which can be degraded by microorganisms into compounds such as carbon dioxide and water, have attracted attention as a possible solution to plastic waste pollution (4). There are several companies currently producing PBSu; the combined production capacity of these companies approaches several million tons per year (5). PBSu biodegradability greatly depends on the environment conditions (6); while it degrades easily in compost (7,8), slowly in soil (9,10), and barely in freshwater, it does not degrade in marine environments (11).

PBSu samples with different molecular weights and relatively narrow polydispersities were prepared by the researchers utilizing preparative chromatography and SEC. PBSu was synthesized using 1,4-butanediol (BD) and succinic acid (SA) under a flow of nitrogen gas at 200 °C. Each fractionated PBSu sample was used for biochemical oxygen demand (BOD) biodegradation testing as a viscous liquid or powdered sample because their molecular weights were too low for a film to form. BOD testing of BD and SA showed that both were effectively mineralized in seawater, indicating that PBSu can undergo biodegradation in seawater if hydrolyzed into monomeric components (2).

While the authors were able to validate the enzymatic hydrolyzation of all the fractionated samples in seawater, and that sufficient low-molecular weight (LMW)-PBSu was ultimately metabolized into inorganic compounds. Additionally, they state that the decrease in the molecular weight of PBSu15 after 190 days implies that PBSu can be used as a biodegradable polymer in marine environments over a very long period. However, LMW-PBSu cannot be used for general-purpose applications, unlike commercially available PBSu with a HMW, due to its poor physical properties. Despite this, the utilization of LMW-PBSu as a biodegradable unit by linking it to disulfide bonds as a stimuli-responsive unit has been previously reported (12,13). The authors believe that the linked PBSu can be molded into a self-standing film with physical properties comparable to those of poly(butylene succinate-co-butylene adipate), another commercially available biodegradable polymer. (2)

Biodegradable pellets. © Pawarun - stock.adobe.com

REFERENCES

1. Polybutylene succinate. Wikipedia. https://en.wikipedia.org/wiki/Polybutylene_succinate (accessed 2025-02-17)

2. Tachibana, Y.: Sawanaka, Y.; Tsutsuba, T.; Suzuki, M.; Hiraishi, M.; Kudo, M.; Torii, J.; Kasuya, K. I. Can Poly(butylene Succinate) Degrade in Seawater? Chemosphere 2025, 374, 144203. DOI: 10.1016/j.chemosphere.2025.144203

3. Jambeck, J. R.; Geyer, R.; Wilcox, C.; Siegler, T. R.; Perryman, M.; Andrady, A.; Narayan, R.; Law, K. L. Plastic Waste Inputs from Land into the Ocean. Science2015, 347, 768-771. DOI: 10.1126/science.1260352

4. Wang, G.-X.; Huang, D.; Ji, J.-H.; Völker, C.; Wurm, F. R. Seawater-Degradable Polymers—Fighting the Marine Plastic Pollution. Adv. Sci. 2021,8, DOI: 2001121. DOI: 10.1002/advs.202001121

5. Mtibe, A.; Muniyasamy, S.; Mokhena, T. C.; Ofosu, O.; Ojijo, V.; John, M. Recent Insight into the Biomedical Applications of Polybutylene Succinate and Polybutylene Succinate-Based Materials. Express Polym. Lett. 2023, 17, 2-28. DOI: 10.3144/expresspolymlett.2023.2

6. Kasuya, K.; Takagi, K.; Ishiwatari, S.; Yoshida, Y.; Doi, Y. Biodegradabilities of Various Aliphatic Polyesters in Natural Waters. Polymer Degradation and Stability. Biodegradable Polymers and Macromolecules 1998, 59, 327-332. DOI: 10.1016/S0141-3910(97)00155-9

7. Anstey, A.; Muniyasamy, S.; Reddy, M. M.; Misra, M.; Mohanty, A. Processability and Biodegradability Evaluation of Composites from Poly(butylene Succinate) (PBS) Bioplastic and Biofuel Co-Products from Ontario. J. Polym. Environ.2014, 22, 209-218. DOI: 10.1007/s10924-013-0633-8

8. Zhao, J.; Wang, X.; Zeng, J.; Yang, G.; Shi, F.; Yan, Q. Biodegradation of Poly(butylene Succinate) in Compost. J. Appl. Polym. Sci.2005, 97, 2273-2278. DOI: 10.1002/app.22009

9. Baba, T.; Tachibana, Y.; Suda, S.; Kasuya, K. Evaluation of Environmental Degradability Based on the Number of Methylene Units in Poly(butylene n-Alkylenedionate). Polym. Degrad. Stab.2017, 138, 18-26. DOI: 10.1016/j.polymdegradstab.2017.02.007

10. Nelson, T. F.; Baumgartner, R.; Jaggi, M.; Bernasconi, S. M.; Battagliarin, G.; Sinkel, C.; Künkel, A.; Kohler, H.-P. E.; McNeill, K.; Sander, M. Biodegradation of Poly(butylene Succinate) in Soil Laboratory Incubations Assessed by Stable Carbon Isotope Labelling. Nat. Commun.2022, 13, 5691. DOI: 10.1038/s41467-022-33064-8

11. Jambeck, J. R.; Geyer, R.; Wilcox, C.; Siegler, T. R.; Perryman, M.; Andrady, A.; Narayan, R.; Law. K. L. Plastic Waste Inputs from Land into the Ocean. Science 2015, 347, 768-771. DOI: 10.1126/science.1260352

12. Tachibana, Y.; Baba, T.; Kasuya, K. Environmental Biodegradation Control of Polymers by Cleavage of Disulfide Bonds. Polym. Degrad. Stab.2017, 137, 67-74. DOI: 10.1016/j.polymdegradstab.2017.01.003

13. Tsutsuba, T.; Tachibana, Y.; Shimizu, M.; Kasuya, K. Marine Biodegradation of Poly(butylene succinate) Incorporating Disulfide Bonds Triggered by a Switch Function in Response to Reductive Stimuli.ACS Appl. Polym. Mater. 2023, 5, 2964-2970. DOI: 10.1021/acsapm.3c00147