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Volume 18
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10.3390/polym18020248
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This is an early access version, the complete PDF, HTML, and XML versions will be available soon.
Article

Methanotrophic Poly(hydroxybutyrate) Through C1 Fermentation and Downstream Process Development: Molar Mass, Thermal and Mechanical Characterization

by
Maximilian Lackner
1,*,
Ľubomíra Jurečková
2,
Daniela Chmelová
2,
Miroslav Ondrejovič
2,
Katarína Borská
3,
Anna Vykydalová
3,
Michaela Sedničková
3,
Hamed Peidayesh
3,
Ivan Chodák
3 and
Martin Danko
3,*
1
CIRCE Biotechnologie GmbH, Kerpengasse 125, 1210 Wien, Austria
2
Institute of Biology and Biotechnology, Faculty of Natural Sciences, University of Ss. Cyril and Methodius, 917 01 Trnava, Slovakia
3
Polymer Institute, Slovak Academy of Sciences, Dúbravská cesta 9, 845 41 Bratislava, Slovakia
*
Authors to whom correspondence should be addressed.
Polymers 2026, 18(2), 248; https://doi.org/10.3390/polym18020248
Submission received: 6 November 2025 / Revised: 6 January 2026 / Accepted: 7 January 2026 / Published: 16 January 2026
(This article belongs to the Section Biobased and Biodegradable Polymers)
Versions Notes

Abstract

Today, PHB and its copolymers—potential plastic substitutes—are produced by fermenting sugar, which is not scalable to the volumes of plastic consumption. PHB from CH4 can offer a sustainable process route, with CH4 potentially produced from a variety of waste biomass streams through anaerobic digestion, gasification, and methanation. The high molar mass (Mw) of PHB is a key determinant of its mechanical properties, and strain, culture conditions and downstream processing influence it. In this work, the strain Methylocystis sp. GB 25 (DSMZ 7674) was grown on natural gas as the sole carbon and energy source and air (1:1) in a loop reactor with 350 L active fermentation volume, at 35 °C and ambient pressure. After two days of continuous growth, the bacteria were limited in P and N for 1, 2, and 2.5 days to determine the optimal conditions for PHB accumulation and the highest Mw as the target. The biomass was then centrifuged and spray-dried. For downstream processing, chloroform solvent extraction and selected enzymatic treatment were deployed, yielding ~40% PHB from the biomass. The PHB obtained by solvent extraction exhibited high average weight molar masses of Mw ~1.1–1.5 × 106 g mol−1. The highest Mw was obtained after one day of limitation, whereas enzyme treatment resulted in partially degraded PHB. Cold chloroform maceration, interesting due to energy savings, did not achieve sufficient extraction efficiency because it was unable to extract high-molar-mass PHB fractions. The extracted PHB has a high molar mass, more than double that of standard commercial PHB, and was characterized by DSC, which showed a high degree of crystallinity of up to 70% with a melting temperature of close to 180 °C. Mechanical tensile properties measurements, as well as dynamic mechanical thermal analysis (DMTA), were performed. Degradation of the PHB by enzymes was also determined. Methanotrophic PHB is a promising bioplastics material. The high Mw can limit and delay polymer degradation in practical processing steps, making the material more versatile and robust.
Keywords: gas fermentation; methanotroph; polyhydroxyalkanoates (PHA); solvent extraction; enzymatic treatment; process window gas fermentation; methanotroph; polyhydroxyalkanoates (PHA); solvent extraction; enzymatic treatment; process window

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MDPI and ACS Style

Lackner, M.; Jurečková, Ľ.; Chmelová, D.; Ondrejovič, M.; Borská, K.; Vykydalová, A.; Sedničková, M.; Peidayesh, H.; Chodák, I.; Danko, M. Methanotrophic Poly(hydroxybutyrate) Through C1 Fermentation and Downstream Process Development: Molar Mass, Thermal and Mechanical Characterization. Polymers 2026, 18, 248. https://doi.org/10.3390/polym18020248

AMA Style

Lackner M, Jurečková Ľ, Chmelová D, Ondrejovič M, Borská K, Vykydalová A, Sedničková M, Peidayesh H, Chodák I, Danko M. Methanotrophic Poly(hydroxybutyrate) Through C1 Fermentation and Downstream Process Development: Molar Mass, Thermal and Mechanical Characterization. Polymers. 2026; 18(2):248. https://doi.org/10.3390/polym18020248

Chicago/Turabian Style

Lackner, Maximilian, Ľubomíra Jurečková, Daniela Chmelová, Miroslav Ondrejovič, Katarína Borská, Anna Vykydalová, Michaela Sedničková, Hamed Peidayesh, Ivan Chodák, and Martin Danko. 2026. "Methanotrophic Poly(hydroxybutyrate) Through C1 Fermentation and Downstream Process Development: Molar Mass, Thermal and Mechanical Characterization" Polymers 18, no. 2: 248. https://doi.org/10.3390/polym18020248

APA Style

Lackner, M., Jurečková, Ľ., Chmelová, D., Ondrejovič, M., Borská, K., Vykydalová, A., Sedničková, M., Peidayesh, H., Chodák, I., & Danko, M. (2026). Methanotrophic Poly(hydroxybutyrate) Through C1 Fermentation and Downstream Process Development: Molar Mass, Thermal and Mechanical Characterization. Polymers, 18(2), 248. https://doi.org/10.3390/polym18020248

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