Synthetic Biology & Carbon Capture
The polluting drift of the first world is a consequence of a poor understanding of the side effects of burning fossil fuels. This poor vision is fundamentally due to the absence of better energy technology during the industrial revolutions and has been perpetuated to the present day. This unsustainable model of production has been installed in the industry for decades, and it does not seem so easy to move all the pieces of the board, despite the scientific evidence that we are turning the planet into an almost irremediable landfill.
We say almost because for every problem there is always a way to solve it. Of course, we are talking about biotechnology.
Why is it called carbon capture?
As you may well know, living things are composed of a chemical carbon pool. It is precisely this chemical variability possessed by the covalent carbon bonds that there is certain stability necessary to sustain living things. These chemical systems are very persistent at a general level, even though there are species that are very sensitive to external changes. This means that this carbon has to come from somewhere and is fixed in the biosphere. This fixation is so powerful that it can only be undone by combustion or phosphorylating oxidation that heterotrophs themselves commit. Today we know that living things continuously fix atmospheric CO2 through photosynthesis and other processes such as the reverse TCA pathway.
Of course, this process, which is carried out continuously by trillions of organisms, has been overtaken by a higher concentration of this gas in the troposphere. Some say that since rubisco is an enzyme that evolved under conditions of higher partial pressure of CO2, this increase could be buffered by greater efficiency in photosynthesis. The evidence, however, says otherwise, as atmospheric CO2 levels continue to rise alarmingly. That is why biotechnology is trying to develop a method to significantly improve this natural fixation of the famous greenhouse gas, hence the name. Other names such as carbon-neutral are often given to alternatives that emit CO2, but their production also fixes the same or similar CO2.
How to improve the natural ratio?
One of the most remarkable facts that scientists noticed was that the carboxylases we found in living beings were not efficient enough, as they did not have a high affinity for carbon dioxide at partial pressures in vivo and also in vitro, the latter conditions being much less tolerable for the reaction. A multitude of approaches has been proposed to overcome these limitations. To find carboxylases that are able to withstand higher temperatures in a type of organism called thermophiles, extremophiles capable of surviving at temperatures close to protein denaturation or even exceeding it in some cases. Other plausible lines of research are to carry out directed evolution in thermostable proteins that maintain carboxylase activity, or successful enzyme immobilization; an ingenious biotechnological response to problems of this type.
However, other strategies have emerged over time and are currently considered more interesting for this purpose. Photosynthetic engineering in archaeplastidia has a promising future in both industry and scientific knowledge, as it would allow plants to increase the rate of atmospheric fixation to significantly higher levels. They would do this by modifying the physiology that evolution has designed for them, through a battery of genetic interventions. These include modified carboxysomes, responsible for storing carboxylases more efficiently; directly modifying carboxylases to increase affinity; modifying the thylakoid membrane and the optical structure inside the leaf/chloroplast; designing a system of antennae to capture energy from other wavelengths, allowing photosynthesis in deeper layers of the ocean where less light reaches, etc.
The strategies described above can be used for extensive crop planting, thus solving two problems at once: pollution and crop yield. However, terrestrial plants are highly inefficient at fixing carbon, contrary to popular belief. Green algae – chlorophytes – have been shown to be far more efficient at this task, as their division ratio can be artificially increased to ridiculous numbers. In addition to the above, as they are liquid cultures, they combine more technologies to increase yield, such as the development of cultivation stations efficiently distributed so that light has a maximum dispersion, avoiding the shadow effect that the cell concentration itself initiates (turbidity of the medium prevents maximum yield), circular economy of the by-products generated in this reaction, generation of biofuels that are more energetically favorable, and a long etcetera.
Current State & Start-ups
In line with what we have been talking about, we have many initiatives taking advantage of this new biomass raw material, whose value has been made profitable not only by the intrinsic cost of the material but also by the CO2 that it contains and has not been released into the atmosphere, immobilized forever in a formidable object. Other strategies, such as that of Hexas Biomass, consist of using non-wood biomass for animal feed. Others use bioethanol and derivatives from biomass production to add ecological value to the product, such as C Capture or LanzaTech.
While at present this market competes with large chemical or industrial capture initiatives, in the medium-term future we will see how a necessarily biotechnological model will be implemented, since the exponential reproduction capacity of living beings is unmatched by human technology, for the time being. If we play our cards right, we will have a chance to change the catastrophic future of the world. At least, catastrophic for the quality of human life.
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