Abstract
Background
Polyhydroxyalkanoates (PHAs), biodegradable polymers, can be synthesised and degraded by a number of bacteria. With a range of monomer composition and molecular weight, these polymers can be used from packaging to medical applications. However, the production cost, inadequate mechanical properties and challenging melt processing properties are major impediments.
Understanding and harnessing the regulatory networks underpinning PHA production in a model organism Pseudomonas putida KT2440 is an invaluable tool to increase PHA production and alter polymer properties for specific applications.
Results
The small RNAs CrcY and CrcZ, key components of the carbon catabolite repression (CCR) system are implicated in PHA metabolism in P. putida KT2440. Their in trans overexpression in P. putida KT2440 shows 1.3- to 3.5-fold increase in PHA titre (g/L), using glucose or octanoate as feedstocks. This is accompanied by a decrease in the Mw of the synthesised polymer. Among the proteins showing differential expression in response to CrcY and CrcZ overexpression, glutaryl-CoA dehydrogenase GcdH involved in the catabolism of lysine, hydroxylysine, and tryptophan, and gamma-glutamyl transpeptidase GGT involved in the glutathione metabolism, showed a consistent increase in abundance across different conditions. It also appears that CrcY and CrcZ can compensate each other, as only when both sRNAs are removed a 2.5-fold decrease in PHA is observed. We also show that these sRNAs require other CCR elements, Hfq and Crc for their role in PHA metabolism.
Conclusions
One strategy to overcome poor mechanical properties of PHAs is to blend them with a second polymer. Medium chain length (mcl)-PHA acts as a plasticiser when blended with poly-3-hydroxybutyrate (PHB), the most widespread used PHA resin. Here we show a clear effect of the overexpression of CCR elements CrcY and CrcZ in P. putida KT2440 on the amount of the accumulated mcl-PHA and its Mw, making this tool valuable to produce mcl-PHA based additives.
These findings highlight the complementary regulatory roles of CrcY and CrcZ in modulating CCR to optimise PHA production. This study provides insights into leveraging CCR elements to enhance the efficiency of PHA biosynthesis, contributing to the development of sustainable bioplastic production.
Polyhydroxyalkanoates (PHAs), biodegradable polymers, can be synthesised and degraded by a number of bacteria. With a range of monomer composition and molecular weight, these polymers can be used from packaging to medical applications. However, the production cost, inadequate mechanical properties and challenging melt processing properties are major impediments.
Understanding and harnessing the regulatory networks underpinning PHA production in a model organism Pseudomonas putida KT2440 is an invaluable tool to increase PHA production and alter polymer properties for specific applications.
Results
The small RNAs CrcY and CrcZ, key components of the carbon catabolite repression (CCR) system are implicated in PHA metabolism in P. putida KT2440. Their in trans overexpression in P. putida KT2440 shows 1.3- to 3.5-fold increase in PHA titre (g/L), using glucose or octanoate as feedstocks. This is accompanied by a decrease in the Mw of the synthesised polymer. Among the proteins showing differential expression in response to CrcY and CrcZ overexpression, glutaryl-CoA dehydrogenase GcdH involved in the catabolism of lysine, hydroxylysine, and tryptophan, and gamma-glutamyl transpeptidase GGT involved in the glutathione metabolism, showed a consistent increase in abundance across different conditions. It also appears that CrcY and CrcZ can compensate each other, as only when both sRNAs are removed a 2.5-fold decrease in PHA is observed. We also show that these sRNAs require other CCR elements, Hfq and Crc for their role in PHA metabolism.
Conclusions
One strategy to overcome poor mechanical properties of PHAs is to blend them with a second polymer. Medium chain length (mcl)-PHA acts as a plasticiser when blended with poly-3-hydroxybutyrate (PHB), the most widespread used PHA resin. Here we show a clear effect of the overexpression of CCR elements CrcY and CrcZ in P. putida KT2440 on the amount of the accumulated mcl-PHA and its Mw, making this tool valuable to produce mcl-PHA based additives.
These findings highlight the complementary regulatory roles of CrcY and CrcZ in modulating CCR to optimise PHA production. This study provides insights into leveraging CCR elements to enhance the efficiency of PHA biosynthesis, contributing to the development of sustainable bioplastic production.
| Original language | English |
|---|---|
| Journal | Biotechnology for biofuels and bioproducts |
| Publication status | Accepted/In press - 19 Sept 2025 |