Polyhydroxyalkanoates consisting of α-methylated monomers: current progress in biosynthesis, material properties, and biodegradation
Source abstract
Abstract
Abstract This review focuses on the biosynthesis, material properties, and potential applications of α-methylated polyhydroxyalkanoates (PHAs), a subclass of biodegradable polyesters produced by microbial fermentation. Emphasis is placed on monomers such as 3-hydroxy-2-methylbutyrate (3H2MB), 3-hydroxy-2-methylpropionate (3H2MP), 3-hydroxypivalate (3HPi), and α-methylated thioester 3-methyl-2-mercaptopropionate (3M2MP), which contribute to the unique properties of these polymers. The incorporation of α-methyl groups into PHA monomers enhances thermal stability and mechanical strength compared to non-substituted PHAs, while maintaining their biodegradability, making them attractive candidates for sustainable bioplastics. This review also summarizes the known microbial pathways and enzymatic mechanisms responsible for synthesizing these α-methylated PHAs, highlighting key enzymes and metabolic routes. These advancements suggest that α-methylated PHAs can overcome some limitations of conventional PHAs, such as brittleness and low thermal stability, thereby expanding their potential industrial applications in packaging, biomedical devices, and other fields. Overall, this review provides an updated overview of α-methylated PHA biosynthesis and properties, underscoring their importance in developing environmentally friendly alternatives to petroleum-based plastics.
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Research context
OpenAlex topics: biodegradable polymer synthesis and properties · Carbon dioxide utilization in catalysis · Microplastics and Plastic Pollution
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References (67)
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1. Steinbüchel, A. Polyhydroxyalkanoic acids. In Biomaterials: Novel Materials from Biological Sources, 123–213 (Palgrave Macmillan UK, 1991).10.1007/978-1-349-11167-1_3 ↗
2. Anderson, A. J. & Dawes, E. A. Occurrence, metabolism, metabolic role, and industrial uses of bacterial polyhydroxyalkanoates. Microbiol. Rev. 54, 450–472 (1990).10.1128/mr.54.4.450-472.1990 ↗
3. Chen, G.-Q. A microbial polyhydroxyalkanoates (PHA) based bio-and materials industry. Chem. Soc. Rev. 38, 2434–2446 (2009).10.1039/b812677c ↗
4. Satoh, H., Mino, T. & Matsuo, T. PHA production by activated sludge. Int. J. Biol. Macromol. 25, 105–109 (1999).10.1016/S0141-8130(99)00021-5 ↗
5. Pisco, A. R., Bengtsson, S., Werker, A., Reis, M. A. M. & Lemos, P. C. Community structure evolution and enrichment of glycogen-accumulating organisms producing polyhydroxyalkanoates from fermented molasses. Appl. Environ. Microbiol. 75, 4676–4686 (2009).10.1128/AEM.02486-08 ↗
6. Bengtsson, S., Pisco, A. R., Johansson, P., Lemos, P. C. & Reis, M. A. M. Molecular weight and thermal properties of polyhydroxyalkanoates produced from fermented sugar molasses by open mixed cultures. J. Biotechnol. 147, 172–179 (2010).10.1016/j.jbiotec.2010.03.022 ↗
7. Zainab-L, I., Uyama, H., Li, C., Shen, Y. & Sudesh, K. Production of polyhydroxyalkanoates from underutilized plant oils by Cupriavidus necator. CLEAN–Soil Air Water 46, 1700542 (2018).10.1002/clen.201700542 ↗
8. Mohd Fadzil, F. I., Tsuge, T. Bioproduction of polyhydroxyalkanoate from plant oils. In Microbial Applications Vol. 2: Biomedicine, Agriculture and Industry, 231–260 (2017).10.1007/978-3-319-52669-0_13 ↗
9. Mohd Fadzil, F. I., Mizuno, S., Hiroe, A., Nomura, C. T. & Tsuge, T. Low carbon concentration feeding improves medium-chain-length polyhydroxyalkanoate production in Escherichia coli strains with defective β-oxidation. Front. Bioeng. Biotechnol. 6, 178 (2018).10.3389/fbioe.2018.00178 ↗
10. Vermeer, C. M., Bons, L. J. & Kleerebezem, R. Production of a newly discovered PHA family member with an isobutyrate-fed enrichment culture. Appl. Microbiol. Biotechnol. 106, 605–618 (2022).10.1007/s00253-021-11742-9 ↗
11. Miyahara, Y., Wang, C.-T., Ishii-Hyakutake, M. & Tsuge, T. Continuous supply of non-combustible gas mixture for safe autotrophic culture to produce polyhydroxyalkanoate by hydrogen-oxidizing bacteria. Bioengineering 9, 586 (2022).10.3390/bioengineering9100586 ↗
12. Sathiyanarayanan, G. & Esteves, S. Autotrophic bacterial production of polyhydroxyalkanoates using carbon dioxide as a sustainable carbon source. Front. Bioeng. Biotechnol. 13, 1545438 (2025).10.3389/fbioe.2025.1545438 ↗
13. Tanaka, K., Orita, I. & Fukui, T. Efficient production of high-concentration poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) from CO2 employing the recombinant of Cupriavidus necator. Bioengineering 12, 557 (2025).10.3390/bioengineering12060557 ↗
14. Tsuge, T. Metabolic improvements and use of inexpensive carbon sources in microbial production of polyhydroxyalkanoates. J. Biosci. Bioeng. 94, 579–584 (2002).10.1016/S1389-1723(02)80198-0 ↗
15. Sivashankari, R., Tsuge, T. in Environmental Pollution and Remediation (ed. Prasad, R.) Development of polyhydroxyalkanoate (PHA) and its copolymers as a possible “cure” for the plastic pollution, 59-79 (Springer Singapore, 2021).10.1007/978-981-15-5499-5_3 ↗
16. Wallen, L. L. & Rohwedder, W. K. Poly-β-hydroxyalkanoate from activated sludge. Environ. Sci. Technol. 8, 576–579 (1974).10.1021/es60091a007 ↗
17. Shimamura, E. et al. Physical properties and biodegradability of microbial poly(3-hydroxybutyrate-co-3-hydroxyhexanoate). Macromolecules 27, 878–880 (1994).10.1021/ma00081a041 ↗
18. Kobayashi, G., Shiotani, T., Shima, Y., Doi, Y. Biosynthesis and characterization of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) from oils and fats by Aeromonas sp. OL-338 and Aeromonas sp. FA-440. In Studies in Polymer Science Vol. 12, 410–416 (Elsevier, 1994).10.1016/B978-0-444-81708-2.50044-0 ↗
19. Hachisuka, S.-I. et al. Isolation and characterization of polyhydroxyalkanoate-degrading bacteria in seawater at two different depths from Suruga Bay. Appl. Environ. Microbiol. 89, e01488–23 (2023).10.1128/aem.01488-23 ↗
20. Omura, T. et al. Microbial decomposition of biodegradable plastics on the deep-sea floor. Nat. Commun. 15, 568 (2024).10.1038/s41467-023-44368-8 ↗
21. Watanabe, Y., Ishizuka, K., Furutate, S., Abe, H. & Tsuge, T. Biosynthesis and characterization of novel poly(3-hydroxybutyrate-co-3-hydroxy-2-methylbutyrate): thermal behavior associated with α-carbon methylation. RSC Adv. 5, 58679–58685 (2015).10.1039/C5RA08003G ↗
22. Zhou, Z., LaPointe, A. M., Shaffer, T. D. & Coates, G. W. Nature-inspired methylated polyhydroxybutyrates from C1 and C4 feedstocks. Nat. Chem. 15, 856–861 (2023).10.1038/s41557-023-01187-0 ↗
23. Furutate, S. et al. Superior thermal stability and fast crystallization behavior of a novel, biodegradable α-methylated bacterial polyester. NPG Asia Mater. 13, 31 (2021).10.1038/s41427-021-00296-x ↗
24. Sudesh, K., Abe, H. & Doi, Y. Synthesis, structure and properties of polyhydroxyalkanoates: biological polyesters. Prog. Polym. Sci. 25, 1503–1555 (2000).10.1016/S0079-6700(00)00035-6 ↗
25. Peters, V. & Rehm, B. H. A. In vivo monitoring of PHA granule formation using GFP-labeled PHA synthases. FEMS Microbiol. Lett. 248, 93–100 (2005).10.1016/j.femsle.2005.05.027 ↗
26. Tsuge, T. Fundamental factors determining the molecular weight of polyhydroxyalkanoate during biosynthesis. Polym. J. 48, 1051–1057 (2016).10.1038/pj.2016.78 ↗
27. Rehm, B. H. Polyester synthases: Natural catalysts for plastics. Biochem. J. 376, 15–33 (2003).10.1042/bj20031254 ↗
28. Sivashankari, R. M. et al. Exploring Class I polyhydroxyalkanoate synthases with broad substrate specificity for polymerization of structurally diverse monomer units. Front. Bioeng. Biotechnol. 11, 1114946 (2023).10.3389/fbioe.2023.1114946 ↗
29. Tsuge, T., Hyakutake, M. & Mizuno, K. Class IV polyhydroxyalkanoate (PHA) synthases and PHA-producing Bacillus. Appl. Microbiol. Biotechnol. 99, 6231–6240 (2015).10.1007/s00253-015-6777-9 ↗
30. Matsumoto, K., Matsusaki, H., Taguchi, K., Seki, M. & Doi, Y. Isolation and characterization of polyhydroxyalkanoates inclusions and their associated proteins in Pseudomonas sp. 61-3. Biomacromolecules 3, 787–792 (2002).10.1021/bm025516k ↗
31. Ishii-Hyakutake, M., Mizuno, S. & Tsuge, T. Biosynthesis and characteristics of aromatic polyhydroxyalkanoates. Polymers 10, 1267. (2018).10.3390/polym10111267 ↗
32. Tsuge, T. et al. Mutation effects of a conserved alanine (Ala510) in type I polyhydroxyalkanoate synthase from Ralstonia eutropha on polyester biosynthesis. Macromol. Biosci. 4, 963–970 (2004).10.1002/mabi.200400075 ↗
33. Tsuge, T. et al. Combination of N149S and D171G mutations in Aeromonas caviae polyhydroxyalkanoate synthase and impact on polyhydroxyalkanoate biosynthesis. FEMS Microbiol. Lett. 277, 217–222 (2007).10.1111/j.1574-6968.2007.00958.x ↗
34. Chek, M. F. et al. Structures of polyhydroxyalkanoate synthase PhaC from Aeromonas caviae, producing biodegradable plastics. Angew. Chem. Int. Ed. e202504626 (2025).
35. Satoh, H., Mino, T. & Matsuo, T. Anaerobic uptake of glutamate and aspartate by enhanced biological phosphorus removal activated sludge. Water Sci. Technol. 37, 579–582 (1998).10.2166/wst.1998.0721 ↗
36. Singh, M., Kumar, P., Ray, S. & Kalia, V. C. Challenges and opportunities for customizing polyhydroxyalkanoates. Indian J. Microbiol. 55, 235–249 (2015).10.1007/s12088-015-0528-6 ↗
37. Satoh, H., Takabatake, H., Mino, T., Matsuo, T. Synthesis of biopolyesters by microorganisms in activated sludge. In Advances in Water and Wastewater Treatment Technology, 249–260 (Elsevier Science BV, 2001).10.1016/B978-044450563-7/50208-0 ↗
38. Michinaka, A., Arou, J., Onuki, M., Satoh, H. & Mino, T. Analysis of polyhydroxyalkanoate (PHA) synthase gene in activated sludge that produces PHA containing 3-hydroxy-2-methylvalerate. Biotechnol. Bioeng. 96, 871–880 (2007).10.1002/bit.21085 ↗
39. Dong, H., Liffland, S., Hillmyer, M. A. & Chang, M. C. Y. Engineering in vivo production of α-branched polyesters. J. Am. Chem. Soc. 141, 16877–16883 (2019).10.1021/jacs.9b08585 ↗
40. Furutate, S. et al. Biosynthesis and characterization of novel polyhydroxyalkanoate copolymers consisting of 3-hydroxy-2-methylbutyrate and 3-hydroxyhexanoate. J. Polym. Res. 24, 1–8 (2017).10.1007/s10965-017-1392-3 ↗
41. Mierzati, M. et al. Tacticity characterization of biosynthesized polyhydroxyalkanoates containing (S)- and (R)-3-hydroxy-2-methylpropionate units. Biomacromolecules 25, 444–454 (2023).10.1021/acs.biomac.3c01069 ↗
42. Wang, C.-T., Sivashankari, R. M., Miyahara, Y. & Tsuge, T. Polyhydroxyalkanoate copolymer production by recombinant Ralstonia eutropha strain 1F2 from fructose or carbon dioxide as sole carbon source. Bioengineering 11, 455 (2024).10.3390/bioengineering11050455 ↗
43. Mierzati, M. et al. Biosynthesis, characterization, and biodegradation of elastomeric polyhydroxyalkanoates consisting of α-dimethylated monomer units. Mater. Today Sustain. 24, 100577 (2023).
44. Miyahara, Y. et al. Thermal and crystallization properties of a polyhydroxyalkanoate binary copolymer containing 3-hydroxybutyrate and 3-hydroxy-2-methylvalerate units. Processes 11, 1901 (2023).10.3390/pr11071901 ↗
45. Miyahara, Y. et al. Biosynthesis of polyhydroxyalkanoate copolymers consisting of α-methylated monomer units from glucose and propionate: thermal properties and chiral configuration. Biotechnol. Sustain. Mater. 1, 7 (2024).10.1186/s44316-024-00008-9 ↗
46. Zhou, L. et al. Chemically circular, mechanically tough, and melt-processable polyhydroxyalkanoates. Science 380, 64–69 (2023).10.1126/science.adg4520 ↗
47. Dai, Y., Lambert, L., Yuan, Z. & Keller, J. Characterization of polyhydroxyalkanoate copolymer with controllable four-monomer composition. J. Biotechnol. 134, 137–145 (2008).10.1016/j.jbiotec.2008.01.013 ↗
48. Jiang, Y., Chen, Y. & Zheng, X. Efficient polyhydroxyalkanoates production from a waste-activated sludge alkaline fermentation liquid by activated sludge submitted to the aerobic feeding and discharge process. Environ. Sci. Technol. 43, 7734–7741 (2009).10.1021/es9014458 ↗
49. Furutate, S., Abe, H. & Tsuge, T. Thermal properties of poly(3-hydroxy-2-methylbutyrate-co-3-hydroxybutyrate) copolymers with narrow comonomer-unit compositional distributions. Polym. J. 53, 1451–1457 (2021).10.1038/s41428-021-00545-4 ↗
50. Hou, X. et al. Entropy-driven ultratough blends from brittle polymers. ACS Macro Lett. 10, 406–411 (2021).10.1021/acsmacrolett.0c00844 ↗
51. Escapa, I. F. et al. Disruption of β-oxidation pathway in Pseudomonas putida KT2442 to produce new functionalized PHAs with thioester groups. Appl. Microbiol. Biotechnol. 89, 1583–1598 (2011).10.1007/s00253-011-3099-4 ↗
52. Lütke-Eversloh, T. et al. Biosynthesis of novel thermoplastic polythioesters by engineered Escherichia coli. Nat. Mater. 1, 236–240 (2002).10.1038/nmat773 ↗
53. Lütke-Eversloh, T., Bergander, K., Luftmann, H. & Steinbüchel, A. Identification of a new class of biopolymer: bacterial synthesis of a sulfur-containing polymer with thioester linkages. Microbiology 147, 11–19 (2001).10.1099/00221287-147-1-11 ↗
54. Wang, L.-Y., Ren, W.-M. Synthesis of polythioesters. In Sulfur-Containing Polymers: From Synthesis to Functional Materials, 171–190 (2021).10.1002/9783527823819.ch5 ↗
55. Lütke-Eversloh, T. & Steinbüchel, A. Microbial polythioesters. Macromol. Biosci. 4, 165–174 (2004). (2004).10.1002/mabi.200300084 ↗
56. Yu, F. et al. Mechanical properties of comonomer-compositionally fractionated poly[(3-hydroxybutyrate)-co-(3-mercaptopropionate)] with low 3-mercaptopropionate unit content. Macromol. Biosci. 7, 810–819 (2007). (2007).10.1002/mabi.200600295 ↗
57. Lütke-Eversloh, T., Bergander, K., Luftmann, H. & Steinbüchel, A. Biosynthesis of poly(3-hydroxybutyrate-co-3-mercaptobutyrate) as a sulfur analogue to poly(3-hydroxybutyrate) (PHB). Biomacromolecules 2, 1061–1065 (2001).10.1021/bm015564p ↗
58. Lütke-Eversloh, T. & Steinbüchel, A. Novel precursor substrates for polythioesters (PTE) and limits of PTE biosynthesis in Ralstonia eutropha. FEMS Microbiol. Lett. 221, 191–196 (2003).10.1016/S0378-1097(03)00185-X ↗
59. Ceneviva, L. V. S. et al. Poly(3-mercapto-2-methylpropionate), a novel α-methylated bio-polythioester with rubber-like elasticity, and its copolymer with 3-hydroxybutyrate: biosynthesis and characterization. Bioengineering 9, 228 (2022).10.3390/bioengineering9050228 ↗
60. Saito, Y. & Doi, Y. Microbial synthesis and properties of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) in Comamonas acidovorans. Int. J. Biol. Macromol. 16, 99–104 (1994).10.1016/0141-8130(94)90022-1 ↗
61. Suzuki, M., Tachibana, Y. & Kasuya, K. I. Biodegradability of poly (3-hydroxyalkanoate) and poly (ε-caprolactone) via biological carbon cycles in marine environments. Polym. J. 53, 47–66 (2021).10.1038/s41428-020-00396-5 ↗
62. Ho, Y. H., Gan, S. N. & Tan, I. K. Biodegradation of a medium-chain-length polyhydroxyalkanoate in tropical river water. Appl. Biochem. Biotechnol. 102, 337–347 (2002).10.1385/ABAB:102-103:1-6:337 ↗
63. Wang, S. et al. Biodegradation of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) plastic under anaerobic sludge and aerobic seawater conditions: gas evolution and microbial diversity. Environ. Sci. Technol. 52, 5700–5709 (2018).10.1021/acs.est.7b06688 ↗
64. Narancic, T. et al. Biodegradable plastic blends create new possibilities for end-of-life management of plastics but they are not a panacea for plastic pollution. Environ. Sci. Technol. 52, 10441–10452 (2018).10.1021/acs.est.8b02963 ↗
65. Tsuge, T., Saito, Y., Kikkawa, Y., Hiraishi, T. & Doi, Y. Biosynthesis and compositional regulation of poly[(3-hydroxybutyrate)-co-(3-hydroxyhexanoate)] in recombinant Ralstonia eutropha expressing mutated polyhydroxyalkanoate synthase genes. Macromol. Biosci. 4, 238–242 (2004).10.1002/mabi.200300077 ↗
66. Volova, T. G., Boyandin, A. N. & Prudnikova, S. V. Biodegradation of polyhydroxyalkanoates in natural soils. J. Sib. Fed. Univ. Biol. 8, 152–167 (2015).10.17516/1997-1389-2015-8-2-152-167 ↗
67. Sivashankari, R. M. et al. Characterization of Actinophytocola sp. strain KF-1 newly isolated from humus soil as polyhydroxyalkanoate-degrading bacterium. Polym. Degrad. Stabil. 247, 112017 (2026).10.1016/j.polymdegradstab.2026.112017 ↗