– Dr. Richa Bobade
Sustainable industrialization is much sought after knowing the severe and irreversible damages caused to the environment due to extensive usage of fossil fuels. Carbon dioxide (CO2) is the most commonly produced greenhouse gas by major industrial operations utilizing fossil fuels. The lesser-known fact about CO2 is that it can be used as feedstock for a range of industrial operations. CO2 is a critical industrial building component in everything from plastics to concrete and is generally used to produce low carbon fuel.
Researchers from Lanza Tech, a carbon capture company, and North-western University in Illinois have used synthetic biology to develop the first sustainable and scalable carbon-negative approach for producing acetone and isopropanol (IPA). They are widely used as industrial solvents and to make plastics, including acrylic glass and polypropylene. The production of acetone and propanol is usually done by propene cracking or reforming which are energy-intensive processes producing hazardous greenhouse gases. Acetone and IPA have a combined market value of over $10 billion (£7.4 billion). The group has addressed this issue with a novel idea of using genetically modified bacteria to ferment CO2 to commodity chemicals. This method assures significant environmental benefits besides utilizing low-cost waste gas feedstocks, such as industrial emissions and syngas.
The bacterium, Clostridium autoethanogenum, is known to naturally ferment carbon oxide gases for energy, resulting in ethanol as an end product. The Team selected this bacteria for genetic modification to ferment CO2 to desired chemicals. The entire process of genetic modification and chemical production was carried out in three steps. In the first step, the team mined C. autoethanogenum’s genome for enzymes that brought about the molecular transformation that enabled acetone or IPA production. This step was followed by introducing these enzymes in different strains of bacteria to optimize the production of acetone or IPA. After optimizing the strains for continuous process, the last step included scale-up of the process at an industrial scale in a 120-liter loop reactor connected to a carbon dioxide waste stream from a steel plant. Analyses revealed that the process locks in 1.79kg and 1.17kg of CO2 into acetone and IPA, respectively per kilogram of the end product after offsetting carbon emissions during the process. The findings are published in Nature Biotechnology on February 21.
By using the standard techniques, the discovery and optimization process could have required a years’ time. However, the work was sped up to a matter of a few weeks using vitro cell-free tools. This technique enabled the researchers to control and study biochemical reactions without interference from other complex interactions present in living organisms. Life cycle analysis has confirmed a negative carbon footprint for the end products. The Group leader Micheal Jewett from the University explained that “A key feature is that acetone and isopropanol can be separated using similar technology as ethanol, which allows us to use the same (LanzaTech) plant infrastructure and switch between products by simply changing the microbe.” He further added, “This is a paradigm shift to the chemical industry, where a plant is typically purpose-built for a certain product and production cannot be easily changed.”
The method so developed may pave the way to redefine the future of biomaking of chemicals assuring carbon-negative processes and sustainable industrial production.
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