Unlocking Amorphous Bioplastics: The Power of Gene Deletion in Caldimonas thermodepolymerans

Unlocking Amorphous Bioplastics: The Power of Gene Deletion in Caldimonas thermodepolymerans

Abstract

Polyhydroxyalkanoates (PHA) are natural, biodegradable polymers gaining attention as a promising, sustainable alternative to conventional plastics. For their efficient production, thermophilic bacteria (fitting the Next Generation Industrial Biotechnology concept) are particularly suitable. A notable example is the Gram-negative bacterium Caldimonas thermodepolymerans DSM 15344, which can synthesize poly(3-hydroxybutyrate) (PHB) using 20 g/L xylose, with the polymer reaching up to 87 wt. % of the cellular dry mass (CDM). To enhance its industrial relevance, genetic engineering following synthetic biology principles was employed. We performed targeted gene deletions via homologous recombination to control monomer incorporation and thus improve the overall PHA extensibility. In this work, we compare the biotechnological characteristics and stress robustness of four deletion mutants derived from the wild-type C. thermodepolymerans DSM 15344. The greatest improvement was observed in the KS01 mutant due to the deletion of PHA depolymerase – increased molecular weight of the resulting biopolymer and due to the deletion of 2-methylcitrate synthase – copolymer with a high abundance of 3HV units. When 3 g/L of sodium propionate was added to the culture medium, the 3HV content was determined by gas chromatography to be up to 59 mol% in P(3HB-co-3HV), which resulted in the synthesis of a fully amorphous and thermostable PHA material.

Polyhydroxyalkanoates (PHA) are natural, biodegradable polymers gaining attention as a promising, sustainable alternative to conventional plastics. For their efficient production, thermophilic bacteria (fitting the Next Generation Industrial Biotechnology concept) are particularly suitable. A notable example is the Gram-negative bacterium Caldimonas thermodepolymerans DSM 15344, which can synthesize poly(3-hydroxybutyrate) (PHB) using 20 g/L xylose, with the polymer reaching up to 87 wt. % of the cellular dry mass (CDM). To enhance its industrial relevance, genetic engineering following synthetic biology principles was employed. We performed targeted gene deletions via homologous recombination to control monomer incorporation and thus improve the overall PHA extensibility. In this work, we compare the biotechnological characteristics and stress robustness of four deletion mutants derived from the wild-type C. thermodepolymerans DSM 15344. The greatest improvement was observed in the KS01 mutant due to the deletion of PHA depolymerase – increased molecular weight of the resulting biopolymer and due to the deletion of 2-methylcitrate synthase – copolymer with a high abundance of 3HV units. When 3 g/L of sodium propionate was added to the culture medium, the 3HV content was determined by gas chromatography to be up to 59 mol% in P(3HB-co-3HV), which resulted in the synthesis of a fully amorphous and thermostable PHA material.

thermophiles, polyhydroxyalkanoates, genetic modifications

thermophiles, polyhydroxyalkanoates, genetic modifications

11.11.2025

Brno

978-80-280-0783-6

XXIV. setkání biochemiků a momlekulárních biologů

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81

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