The climate crisis is one of the greatest challenges that we have to face
Since the beginning of industrialisation, greenhouse gas emissions have greatly increased. This increase is mostly due to combustion of fossil fuels for example during industrial processes or for transportation, which leads to the emission of the primary greenhouse gas carbon dioxide (United States Environmental Protection Agency, 2022). Due to the accumulation of greenhouse gases in the atmosphere, thermal radiation is increasingly absorbed, which heats up the surface. This process is called “greenhouse effect” and has already caused severe problems for humanity; emerging global warming, sea level rise, and worldwide weather extremes are just a few examples. Thus, the international community aims to limit global warming according to the Paris climate agreement. Therefore, the global carbon dioxide emission must be reduced by 48% by 2030 compared to 2019 levels (Umweltbundesamt, 2022). But to do so, there is still a long way to go. With our project, we want to contribute to achieving this goal.
Why do we need liquid biofuels?
German politics are currently pursuing the goal of reducing carbon dioxide emissions through the electrification of the transport sector. However, this requires dramatic improvements in renewable electricity production. Furthermore, the infrastructure for charging stations must be expanded and widely distributed internal combustion engine vehicles must be replaced by new electric vehicles (International Energy Agency, 2022). These measures represent both a financial and an environmental burden for the international community and the planet. Another problem is that not all vehicles can be easily electrified. Therefore, a sustainable but also profitable alternative solution is needed for all types of transport vehicles.
(Image sources: https://commons.wikimedia.org/wiki/File:Erneuerbare_Energien_in_Enkenbach-Alsenborn.JPG, Created by: Jan.boedeker, License: Creative Commons Attribution-Share Alike 3.0 Unported license; https://commons.wikimedia.org/wiki/File:Maisfeld_Schneise_Wedemark.jpg, Created by: Axel Hindemith, License: Creative Commons CC-by-sa-3.0 de).
So far, plant-based fuels such as bioethanol have been established. However, land that is used to produce plant-based biofuels cannot be used for food production. This conflict is not compatible with the ever-growing world population and the hunger that more and more people are experiencing today. In addition, the production of plant-based biofuels often involves high feedstock or processing costs that reduce their competitiveness (Singh et al., 2022). For this reason, scientists are focusing on the development of biofuels based on waste materials such as CO2. The use of CO2 as a starting material would create a cycle of alternating CO2 binding and emission by biofuel combustion. But how could such a process be achieved?
Clostridia as microbial platforms for biofuel production from waste gases
Microorganisms can be used to catalyse complex chemical reactions and produce all sorts of chemicals. For our project, we want to exploit the metabolic capabilities of two different types of organisms: Acetogenic and solventogenic bacteria of the Clostridium class. Some acetogenic clostridia are able to assimilate waste gases, including CO2. The so-called “Wood-Ljungdahl Pathway” (WLP) is responsible for the conversion of CO2 and CO to Acetyl-CoA when H2 is present (image 1).
Image 1: Depiction of the Wood-Ljungdahl pathway. CO2 is converted to Acetyl-CoA in presence of H2. (Image modified from Köpke et al., 2013. https://doi.org/10.1371/journal.pone.0062157.g001. License: Creative Commons Attribution License).
Acetyl-CoA is a central metabolite that can be converted into various products. This is, when the second group, the solventogenic Clostridia come into play. As the name suggests, solventogenic Clostridia produce high amounts of solvents. The bacteria we chose for our project, are hyper-butanol-producing strains that also contain most of the genetic prerequisites to assimilate CO2 via the WLP. Our goal is to introduce the missing genes from acetogenic clostridia into the solventogenic clostridia and therewith establish a functional WLP in the hyper-butanol-producing strains. Those engineered strains should then be able to produce biobutanol from waste gases and allow climate-neutral biofuel generation.
Implementation of climate-neutral biobutanol production
An idea should be followed by an implementation. So you may wonder how we plan to use our technology in detail. Waste gases are produced during industrial processes such as steel production and could be collected to feed our engineered clostridial strain. Theoretically, this would be much cheaper than producing plant-based biofuels and would enable competition with fossil fuels. Furthermore, biobutanol has a high energy density, meaning that it is a more efficient fuel than bioethanol, for instance. Moreover, it can be used undiluted to substitute diesel and is compatible with the most widely distributed internal combustion engines. Therefore, the use of biobutanol would be a viable solution to run transport vehicles of all kinds in a climate-neutral way (image 2).
Image 2: Butanol production based on engineered bacteria is CO2-neutral.
iGEM Team Goettingen
Image: Top from left to right: Alexander Rosenberger, Katharina Stark, Sönke Beewen, Lea Hahn, Jasmin Petrovac and Björn Hormes.
Bottom from left to right: Julia Fricke and Lea Trost
We are eight students of the master program “molecular life science” at the Georg‑August University in Göttingen, Germany, and came together to tackle the climate crisis with the help of biotechnology. We were inspired by the idea that waste material can be used to produce fuels in a cheap and climate neutral way. In addition, our project perfectly suited the research interests of the microbiology department of our university. The research group of Prof. Dr. Rolf Daniel has already been working with Clostridia long before we developed our project idea. On this account, Prof. Daniel, Dr. Anja Poehlein and the rest of the AG Daniel group support and mentor us during our work. In the end, we plan to present our results in front of the iGEM jury and international community. iGEM stands for international genetically engineered machine competition and is a great event that takes place every year with visitors from all over the world. This year, the so-called “Grand Jamboree”, where each team presents their project, takes place in Paris by the end of October. We are happy to represent and compete for our university and are looking forward to exchange scientific know how.
For more information about out project, feel free to contact us per mail: igem2022@uni-goettingen.de, or follow us on Instagram: igem.goettingen or YouTube: iGEM Göttingen 2022.
Written and revised by Lea Trost, Lea Hahn, Katharina Stark, Dr. Andreas Ebertz, Julia Fricke, Sönke Beewen, Björn Hormes, Alexander Rosenberger and Jasmin Petrovac
