Carbon capture is a pressing issue as the world struggles to minimise the impact of climate change. A method that has come into the reckoning – metabolic engineering is now being touted as the environmental saviour. The idea is to leverage the power of biological processes to capture and then sequester carbon dioxide (CO2) in the atmosphere or produced in industrial emissions. For those who don’t know what metabolic engineering is, it is a field of biotechnology that focussed on modifying the metabolic pathways of organisms to produce desired compounds or perform specific functions.
We know of several approaches to employing metabolic engineering for carbon capture. The first and most developed is Microbial Carbon Fixation.
Certain microorganisms have the natural ability to fix carbon dioxide from the environment into organic molecules through processes like photosynthesis or chemosynthesis. Metabolic engineering can enhance these processes to increase the efficiency of carbon capture. For instance, biotechnologists can now genetically modify microorganisms like algae or cyanobacteria to enhance their carbon fixation capabilities. By optimizing their metabolic pathways, these organisms can absorb more CO2 from the atmosphere or industrial emissions and convert it into biomass or useful products.
A second approach is through bioenergy production. Metabolic engineering can be applied to develop microorganisms that produce biofuels or biochemicals from CO2. For example, engineered bacteria can convert CO2 into fuels like ethanol, butanol, or methane through metabolic pathways such as the Wood-Ljungdahl pathway. This approach not only captures carbon but also generates renewable energy sources, contributing to a sustainable carbon-neutral cycle.
Of the other approaches, carbon sequestration in plants is a possibility. By modifying the genes responsible for carbon fixation and storage, scientists can develop crops with increased biomass production and carbon sequestration capabilities. This approach involves engineering traits like improved photosynthesis efficiency, increased root biomass, or enhanced carbon storage in plant tissues.
A method that has been occurring for millions of years is biomineralization. Some microorganisms can precipitate carbonate minerals from dissolved bicarbonate ions in their environment, effectively sequestering carbon in the form of solid minerals. Various types of engineering can be used to enhance this biomineralization process in bacteria, enabling them to capture and store carbon in stable mineral forms such as calcium carbonate.
Finally, synthetic biology is a form of metabolic engineering that has been used to modify various microorganisms. Advances in synthetic biology enable the design of novel metabolic pathways or the modification of existing pathways to optimize carbon capture processes. By constructing synthetic biological systems, researchers can engineer microorganisms with enhanced carbon capture and conversion capabilities tailored to specific environmental or industrial requirements.
Those who are exploring the technology have centred on cyanobacteria for carbon capture (Santos-Merino et al., 2020; Pattharaprachayakul et al., 2020). These are photosynthetic bacteria that can directly convert carbon dioxide into all sorts of bioproducts. The types of chemicals produced include sugars, various acids, alcohols and diols and other unusual and interesting chemicals. The authors on both counts discuss the role of metabolic engineering in changing cyanobacteria to improve the production of many different value-added products.
Overall, carbon capture technology using metabolic engineering holds promise as a sustainable approach to mitigating CO2 emissions and combating climate change. However, significant research and development efforts are still needed to optimize these approaches for large-scale implementation and address challenges such as scalability, efficiency, and economic viability.
References
Kumar, R. R., and Prasad, S. (2011). Metabolic engineering of bacteria. Indian J. Microbiol. 51, pp. 403–409
Pattharaprachayakul, N., Choi, J. I., Incharoensakdi, A., & Woo, H. M. (2020). Metabolic engineering and synthetic biology of cyanobacteria for carbon capture and utilization. Biotechnology and Bioprocess Engineering, 25(6), pp. 829-847
Santos-Merino, M., Singh, A. K., & Ducat, D. C. (2019). New applications of synthetic biology tools for cyanobacterial metabolic engineering. Frontiers in Bioengineering and Biotechnology, 7, pp. 33.
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