Carbon roadmap from syngas to polyhydroxyalkanoates in Rhodospirillum rubrum

The gasification of organic waste materials to synthesis gas (syngas), followed by microbial fermentation provides a significant resource for generating bioproducts such as polyhydroxyalkanoates (PHA). The anaerobic photosynthetic bacterium, Rhodospirillum rubrum, is an organism particularly attractive for the bioconversion of syngas into PHAs. In this study, a quantitative physiological analysis of R. rubrum was carried out by implementing GC-MS and HPLC techniques to unravel the metabolic pathway operating during syngas fermentation that leads to PHA production. Further, detailed investigations of the central carbon metabolites using 13C-labeled substrate showed significant CO2 assimilation (of 40 %) into cell material and PHA from syngas carbon fraction. By a combination of quantitative gene expression and enzyme activity analyses, the main role of carboxylases from the central carbon metabolism in CO2 assimilation was shown, where the Calvin Benson-Bassham Cycle (CBB) played a minor role. This knowledge sheds light about the biochemical pathways that contribute to synthesis of PHA during syngas fermentation being valuable information to further optimize the fermentation process.This work has been funded by the EU project SYNPOL (grant agreement n° 311815) under the European Union’s Seventh Framework Programme.Peer reviewe

Carbon roadmap from syngas to polyhydroxyalkanoates in Rhodospirillum rubrum

The gasification of organic waste materials to synthesis gas (syngas), followed by microbial fermentation provides a significant resource for generating bioproducts such as polyhydroxyalkanoates (PHA). The anaerobic photosynthetic bacterium, Rhodospirillum rubrum, is an organism particularly attractive for the bioconversion of syngas into PHAs. In this study, a quantitative physiological analysis of R. rubrum was carried out by implementing GC-MS and HPLC techniques to unravel the metabolic pathway operating during syngas fermentation that leads to PHA production. Further, detailed investigations of the central carbon metabolites using 13C-labeled substrate showed significant CO2 assimilation (of 40 %) into cell material and PHA from syngas carbon fraction. By a combination of quantitative gene expression and enzyme activity analyses, the main role of carboxylases from the central carbon metabolism in CO2 assimilation was shown, where the Calvin Benson-Bassham Cycle (CBB) played a minor role. This knowledge sheds light about the biochemical pathways that contribute to synthesis of PHA during syngas fermentation being valuable information to further optimize the fermentation process.This work has been funded by the EU project SYNPOL (grant agreement n° 311815) under the European Union’s Seventh Framework Programme.Peer reviewe