Explorar a fixação de CO2 como nova via para produção de PHA com bactérias fotossintéticas anoxigénicas

To meet society’s request for sustainable bioplastic production systems this research plan is focused on developing and elucidating the mechanisms of an innovative photosynthetic-based CO2 fixation route that comprises the conversion of CO2 into the biodegradable polymer PHA. The use of CO2 as feedstock in PHA producing technologies is currently a significant challenge since phototrophic organisms usually fixate CO2 into internal carbohydrates (e.g. glycogen). This project aims to overcome this challenge by relying on the utilization of APB. APB thrive in anaerobic environments which allows internal glycogen conversion into PHA, and some APB have the unique capability of fixating CO2 using routes alternative to the Calvin cycle. For example, Chloroflexus aurantiacus is an APB that can make use of the pathway 3-hydroxypropionate bicycle to fixate CO2 into PHA precursors. Hence, this project will approach PHA production both using single strain systems (capable of using such alternative pathways), and using APB mixed cultures for reduced polymer production costs due to the use of non-sterile conditions. A further objective of this project is the optimization of PHA extraction from APB. Downstream processes can substantially contribute to PHA production costs, and although extensive research has been carried out on PHA extraction from aerobic cultures, few reports exist on downstream processing of photosynthetically produced PHA. The existing ones address the typical utilization of organic solvents at lab scale which are not acceptable when developing a sustainable technology. This project aims the development of a downstream process for PHA extraction with non-organic solvents adapted to photosynthetic organisms, particularly to their bacterial cell envelops, while allowing polymer integrity, high recovery yield and purity. In parallel to the development of the APB technology, this project also aims to develop on-line monitoring tools (NIR and RAMAN spectroscopies) to determine process parameters in real time and assist on process control and performance optimization. Few reports have applied on-line monitoring tools to APB systems, although timely information on important process parameters are essential to stable operation. Focus will be given to parameters that are currently measured offline using time demanding methods (PHA, Glycogen), but also to parameters that are specific to APB, like pigments (Bacteriochlorophylls) and internal sulfur granules. The specific goals of this project are: 1 Optimize lab-scale bioprocesses for the conversion of CO2 into PHA using single and mixed APB cultures; 2 Isolate and identify new APB strains capable of using CO2 to produce PHA; 3 Optimize a pilot-scale APB bioprocess for CO2 fixation into PHA with high storage capacity, ready for outdoor implementation; 4 Develop a green PHA extraction method adapted to phototrophic organisms; 5 Develop NIR and RAMAN on-line tools for real time monitoring of process parameters. Overall, this project will simultaneously address two major challenges: plastic pollution and CO2 capture. First, the main product of the project will be a sustainable biodegradable plastic that can be used for packaging, replacing synthetic plastics. Second, the resulting technology will have a positive and direct impact in the environment and will be a technological tool that can help CO2 producing industries to comply with the international frameworks in sustainable practices.