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Biological routes for CO2 conversion into chemical building blocks

Periodic Reporting for period 2 - BioRECO2VER (Biological routes for CO2 conversion into chemical building blocks)

Reporting period: 2019-07-01 to 2020-12-31

The high-level goal of BioRECO2VER is to demonstrate the technical feasibility of more energy efficient and sustainable non-photosynthetic anaerobic and micro-aerobic biotechnological processes for the capture and conversion of CO2 from industrial point sources into 2 valuable platform chemicals, i.e. isobutene and lactate. To overcome several of the existing technical and economic barriers for CO2 conversion by industrial biotechnology, the project will focus on minimizing gas pretreatment costs, maximizing gas transfer in bioreactors, preventing product inhibition, minimizing product recovery costs, reducing footprint and improving scalability. To this end, a hybrid enzymatic process will be investigated for CO2 capture from industrial point sources and conversion of captured CO2 into the targeted end-products will be realized through 3 different microbial platforms which are representative of a much wider range of products and applications. Bioprocess development and optimization will occur along 2 lines: fermentation and bioelectrochemical systems. The 3 microbial platforms will be advanced to TRL 4, and the most promising solution for each target product will be validated at TRL 5 on real off gases.
Emissions from two major emitters of greenhouse gases (cement industry and refining/petrochemical industry) were characterized and the most suitable CO2-rich off gases selected for further testing. Sampling was carried out satisfactorily in the centers of partners PKN ORLEN and GCPV and gas bottles were shipped to the partners for lab trials to adapt enzymes and microorganisms to real offgases.
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.
Significant progress has been made on the knowledge of enzyme and microbial platforms, operational conditions and procedures for the proposed technologies. At the basic level of knowledge, experimental work has provided insightful data and information on the physiology and metabolism of the strains to use for the microbial platforms, which could be further exploited biotechnologically. Additionally, two state-of-the-art technologies, such as high-pressure fermenters and BES, are used to optimize the processes, scale them and validate them with real offgases. The developed process models allow tests of configurations and process conditions before the experimental work and will be further improved with the experimental results. To the best of the authors’ knowledge, this is the first time that a model with this level of detail will be developed and implemented for an integrated Carbon Capture and Utilization (CCU) system involving biological processes for CO2 conversion.
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.
Visualization of project concept