Periodic Reporting for period 2 - BioRECO2VER (Biological routes for CO2 conversion into chemical building blocks)
Reporting period: 2019-07-01 to 2020-12-31
LTU aims to develop a CO2 capture solvent that combines the enzyme carbonic anhydrase (CA) with suitable amine systems. Several enhanced mutants were generated that showed 50% increased resistance to selected flue gas inhibitors compared to the original CA. Moreover, a blend of an amino acid ionic liquid, MDEA (methyldiethanol amine) and CA was developed that displayed a good compromise between enzyme compatibility, absorption rate, capacity and desorption potential. When scaling up the CO2 capture process in a pilot plant, reduction in operation times and energy consumption compared to the reference system could be demonstrated, yielding a pre-treated concentrated gas stream of at least 92% CO2. The set-up is now ready to perform real off gas pre-treatment for validation testing in the project.
Substantial progress has been made on the 3 microbial platforms under investigation. GBE has identified an optimal strain for the development of the Clostridial platform and implemented an isobutene pathway in this strain. Through a combination of implementing the best enzyme variants into the pathway and modifications in the cultivation medium, isobutene production levels could be increased by a factor of 10. EnobraQ has performed metabolic engineering of autotrophic Cupriavidus necator to produce lactate from CO2 and H2. Overexpression of lactate dehydrogenase and deletion of competitive pathways resulted in the improvement of the production of lactate. Further work resulted in significant improvements in the lactate dehydrogenase activity and in biomass production in a bioreactor. CNR developed methods to address an efficient transformation of Thermotoga neapolitana DMS33003 and generated a recombinant strain producing CO2-derived lactate at a 1.7 fold higher level than wild type. For this platform, the bottleneck remains to overtake the production of CO2 from glycolysis.
All three microbial platforms were tested with real offgases: while 2 of them did not show a negative impact of off-gas impurities and demonstrated growth without gas pretreatment, adaptation trials are ongoing for a third one to increase tolerance to impurities.
The three microbial platforms have now also been tested for enhanced bioconversion processes in fermentors and/or bioelectrochemical systems (BES). Biocathodes coated with immobilized proteobacteria have been tested for sustained and increased in situ H2 production in BES. For Cupriavidus, the fermentation process has been upscaled to 10-L scale and the same levels of lactate were produced in BES as in small-scale fermentations. Clostridium strain performance was evaluated in a 10-L fermentor at elevated pressures up to 8 bar, and under various operational conditions. Moreover, a first proof-of-concept was achieved in BES. Finally, the effect of salinity level, buffering agent, carbon and sulfur sources has been investigated on H2 and lactate synthesis in Thermotoga neapolitana and new adapted strains were generated. The set-ups for the validation trials have been designed and the process to acquire them has been initiated or finalized.
The integrated model of the processes has been developed and is continuously updated with the produced information and results. Metabolic studies have been started to try to clarify some unexpected behaviour showed by the microorganisms.
The scope of the techno-economic analysis has been defined thoroughly. Hot-spot analysis showed the critical influence of the conversion yield in the overall economy of the solution. This remains a big challenge for the process optimization activities. Heat management and gas solubility issues were thoroughly investigated and capital costs for fermenters analysed for industrial scale.
A LCA hot spot analysis was performed for further optimization within the project’s technology development. The methodology to assess social acceptance and public perception of the use of CO2 for products has been defined.
The project website and the Zenodo Community were continuously maintained, with open access to the project publications. New project contents was continuously published on the extensive media channels of the nova-Institut and partners. A project video is available online.
To prepare for industrial implementation and contribute to public acceptance, the technological activities is complemented with virtual plant design, economic and sustainability assessments and extensive dissemination.