Novel PHA Platform Synthesized By Anaerobic Mixed Bacteria in a Single Step Gas Fermentation

The project is developing the concept of a novel biotech process for the conversion of CO2 into polyhydroxyalkanoates (PHAs) using anaerobic mixed cultures via single step fermentation; integrating with H2 from renewable energy generation, gasification and industrial off-gases. Medical, packaging, chemical, textile and aquaculture food production are examples of sectors with a growing demand for these biomolecules.
The project aims to establish an understanding of communities' syntrophic interactions, metabolic pathways for PHA synthesis, and reduce bottlenecks for biopolymer accumulation, making a significant contribution towards the development of PHA synthesis using anaerobic metabolism. The project will also provide important insights into the PHA accumulation role in anaerobic bacteria as a stress response mechanism with a wider impact on other anaerobic biotech processes.

The project is being delivered as part of a collaboration between USW, Nitech Solutions and CSIC (Spain). Initial qPCR evaluations have determined that in typical anaerobic digesters, numerous bacteria feature PHA accumulating genes. A selection of anaerobic mixed cultures has been collected from full scale digesters
operating on different feedstocks, using different process designs and inocula treatments have been carried out. These cultures will be evaluated in terms of PHA biosynthesis to establish which ones provide appropriate cultures for anaerobic PHA fermentation inoculants. High rate gas transfer reactors have been successfully
established for mixed cultures where H2 and CO2 are converted to volatile fatty acids as well as CH4. Future work will include specific co-fermentations using CO2 and H2 of a mixture of pure or mixed cultures in a single stage to achieve PHA production.