Skip to main content

Biological routes for CO2 conversion into chemical building blocks

Periodic Reporting for period 1 - BioRECO2VER (Biological routes for CO2 conversion into chemical building blocks)

Reporting period: 2018-01-01 to 2019-06-30

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. The composition data determine which streams are most suitable for which microbial platform, and which pretreatment would be needed to purify and enrich CO2 from the streams. Sampling was carried out satisfactorily in the centers of partners PKN ORLEN and GCPV between the months of March and April. Gas bottles were shipped in May to the partners EnobraQ, Syngip, CNR and LTU for lab trials to adapt enzymes and microorganisms to real offgases.
LTU aims to develop a CO2 capture solvent that has several fold higher absorption rate and lower desorption temperature compared to currently used systems, by utilizing the enzyme carbonic anhydrase (CA) in combination with suitable amine systems. Although a thermostable CA has already been designed from Desulfovibrio vulgaris (DvCA8.0) it was critical to develop a variant of DvCA8.0 with enhanced resistance to these inhibitors without losing its thermostability. Preliminary results show that LTU has several clones with increased resistance to the inhibitors compared to DvCA8.0 of which at least two had between 45-55% increase. To further enhance the durability of enzyme and to facilitate its controlled localization within an absorption plant the enzyme will be immobilized. More understanding of the influence of precipitant and cross-linker on the activity and stability of the enzyme has been gained which is important for future immobilization work.
Substantial progress has also been made on the 3 microbial platforms under investigation. Syngip/GBE has identified an optimal strain for the development of the Clostridial platform and implemented an isobutene pathway in this strain. Extensive work was made on improving the cultivation conditions, optimizing the genetic tools for gene expression and using engineered enzymes of the isobutene pathway for better accumulation in the cell and/or enhanced catalytic properties. In parallel, this microbe has been implemented by classical strain improvement for optimized growth on CO2 as the sole gaseous carbon source.
EnobraQ has performed metabolic engineering of the 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. EnobraQ has also worked to optimize gas fermentation conditions to improve lactate production and economics.
CNR has selected two strains of T. neapolitana with high productivity of L-lactic acid (95% e.e.) for genetic transformation. Furthermore, transcriptomic analysis has identified the key genes involved in fixation of exogenous CO2 in T. neapolitana, and has established the changes in the central carbon metabolism and the increased availability of cellular reductants (e.g. NADH) that are key prerequisite factors for synthesis of lactic acid from environmental CO2.
The enzymatic and microbial platforms are to be tested for enhanced bioconversion processes in adapted set-ups using pressurized reactors and/or bioelectrochemically assisted reactors (BES). In all situations, working conditions are tested to circumvent the gas transfer limitations of poorly soluble gases. So far, batch reactors and chemostats have been used to elucidate optimal operational conditions for microbial growth and product formation, or have been coupled to gas diffusion membranes. Biocathodes coated with immobilized proteobacteria have been tested for sustained H2 production in BES, preventing O2 diffusion. Various electrode materials have been tested and compared in BES with respect to microbial growth. The pressurized reactor has been designed and is currently under construction.
The integrated model of the processes has been developed and will be continuously updated with the produced information and results duri
Significant increases on the knowledge of enzyme and microbial platforms, operational conditions and procedures for the proposed technologies are envisioned at the end of the project. At the basic level of knowledge, experimental work will provide 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, optimization of two state-of-the-art technologies, such as high-pressure and bioelectrochemical reactors, will be used to implement higher production titers and productivities and scale the processes using optimized operational conditions. The developed process models will allow tests of configurations and process conditions before the deployment of the experimental setup. This way, it is a valuable tool to prepare the validation tests in the project. 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 a complete and integrated CCU system involving biological processes for CO2 conversion.
To prepare for industrial implementation and contribute to public acceptance, the technological activities will be complemented with virtual plant design, economic and sustainability assessments and extensive dissemination.
Visualization of project concept