Sustainable

Closing the carbon and nitrogen cycles, a challenge for our century

“Imagine all the people, living life in peace” John Lennon, 1971

This lyric from a famous John Lennon song is a hymn to world peace. This can only be achieved by working together for a sustainable development of our societies. This includes several challenges, environmental, social and economic. The increase of the greenhouse effect linked to human activities and the depletion of energy resources represent high risks against Peace. The carbon budget imbalance is 1.0 gigatonne of CO₂ per year (Global Carbon Project, 2021). Recently, humanity had to deal with major climate issues (see the Human Practices page). Over the last century, due to the release of greenhouse gas in the atmosphere, the global temperature has only kept on rising. Coming dangerously close to +1.5°C since pre-industrial times (threshold set form the Paris agreements), it has become more and more important to deal with global warming (climate.gov). This starts with reducing the amount of greenhouse gasses released into the atmosphere as these are the main driver of this warming. Over the last century, CO₂ emissions have plummeted: +100 ppm since the 19th century (ourworldindata.org) and all of this gas cannot be fully absorbed by the biosphere.

Our project alone cannot resolve this imbalance, but like many others, it opens a way. Our project might, at first, only seem like a drop in the bucket. But, put end to end, many drops can form oceans. Indeed, imagine all the chassis of the world fixing CO₂. Imagine societies that live by carbon neutrality: any CO₂ molecule emitted is fixed to form high-value molecules. This dream is the basis of the CO2CURE project: recycling CO₂ to produce antibiotics. The very idea of implementing artificial autotrophy within such a chassis combines several societal challenges: i) reducing our impact on the climate by building a carbon sink, ii) enabling more countries to produce drugs from carbon-poor environments, iii) limiting competition between food resources and nutrients for the growth of microorganisms of industrial interest.

Figure: CO2CURE, a first step towards carbon neutrality

Carbon neutrality could also be enlarged to the recycling of industrial waste such as glycerol for example to produce molecules of interest.

This concept of “neutrality” can also be extended to the nitrogen cycle, of which certain intermediates (N₂O / nitrous oxide) released into the atmosphere due to the excessive use of fertilizers (NO₃^- / nitrates) also contribute heavily to the greenhouse effect.

Producing antibiotics from inexpensive resources

By building a bacterial strain that is able to metabolize CO₂ to produce molecules of interest, we would be able to reduce CO₂ emissions as well as helping resolve the access to medication crisis. Indeed, we would be able to replace the heterotrophic strains usually used to produce medication by ours, which would reduce carbon emissions as well as production costs as the usual carbon source would be replaced by the over abundant CO₂. In a sense, in the case of autotrophic chassis, CO₂ becomes a cheap resource of interest for the project. A primary matter, present in abundance in the environment, unused, that would enable us to increase production rates of antibiotics. In the perspective of a perfectly completed project, this project could enable faster, cheaper and more local production of antibiotics, thereby preventing transportation-related CO₂ release in the atmosphere.

The main advances of CO2CURE: Recycling CO₂, waste or other pollutants to produce antibiotics

In our project we characterized new key genes encoding RuBisCO and PRK for CO₂ fixation by Streptomyces (see Parts page), prolific producers of antibiotics and other bioactive compounds useful in medicine and agriculture. We also characterized for the first time a Streptomyces strain, Streptomyces bottropensis ATCC 25435 which contains a genomic island encoding the Calvin cycle (see the STREPTObook page). Finally, we have shown that several strains of Streptomyces can produce antibiotics in absence of organic carbon source and by recycling glycerol (see the Proof of concept page). Interestingly, this production of antibiotics can use nitrates, which can eventually allow the purification of water that is too rich in nitrates. This is another possible application and opening of the project in the framework of sustainable development.

The importance of chassis diversification and improvement for synthetic biology advances

While working on this project, we realized how important it was to propose a diversification of the chassis used in synthetic biology. Indeed, some of them have natural properties (presence of a Calvin cycle, ability to produce bioactive compounds) that can accelerate the work on the design of useful, safe and efficient synthetic systems. Very often, the use of original chassis is made difficult by the need to develop a specific know-how. This is why we have dedicated part of the project to the development of the STREPTObook (see the STREPTObook page for the online STREPTObook as well as a pdf download). The STREPTObook opens the doors of knowledge and supports the use of a new chassis of great biotechnological interest. It democratizes the exploitation of the potential of bacteria producing high value-added products including antibiotics. As part of this process we asked other iGEM teams to think about what defines a good chassis. Safety, efficiency but also durability criteria have emerged as priorities in this survey (see Collaboration page).

Conclusion and perspectives: Hope

Meeting with members of civil society (children, relatives) made us realize how important it was to communicate more about the concept of carbon neutrality (see the Human Practices page). We have seen the extent to which autotrophy projects such as CO2CURE could be a source of hope. Some civilians told us “It is nice to know that there are researchers who are working hard on this”. With access to media 24/7, and seeing articles about global warming, poor reports about climate change, and such few articles about what is done to fight it, we realized how global warming is a source of anxiety for our societies. Knowing that synthetic biology projects exist to fight against it is a source of hope for our generations and we hope that, with our project, we will set an example for industries.

We hope our project could make the world take a new turn upon sustainable development. Carbon autotrophy in a widely used bacterial strain for antibiotics production could contribute to improve the future of drug production. With our technology, we are helping to close the carbon cycle using CO₂. We hope our thought process will help industries think about their carbon footprint and find new ways to minimize it.

Also, by allowing a cheaper, faster and possibly more local way of producing antibiotics, we are able to reduce the greenhouse gasses emission caused by transportation (see Implementation webpage). Our project can also be applied to other usage such as solving soil pollution problems. Lastly, our project is a source of hope for all generations. Hope that one day, maybe, global warming will cease. Hope that one day, maybe, the world will be a greener place. Hope that one day, we will be able to live in symbiosis with our world.