Genetically modified bacteria save carbon dioxide
A special type of bacteria living without sun or oxygen produces chemicals from carbon dioxide. The genetically modified germs could thus help industry and the climate.
Carbon dioxide is a greenhouse gas, but it can also serve as an important raw material for the production of various chemical compounds. Some research groups are therefore working to capture CO2 and put it to good use before it enters the atmosphere. A team of researchers now describes inNature Biotechnologyan advance that turns carbon dioxide into industrially useful basic chemical building blocks in respectable quantities by genetically engineered bacteria.
To do this, the team used genetic engineering to modify Clostridium autoethanogenum bacteria. These so-called autotrophic bacteria belong to the acetogens; their metabolism thus utilizes various small organic molecules with one or a few carbon atoms without sunlight or oxygen. They essentially gain energy through carbonate respiration, transferring electrons from hydrogen to CO2, for example. The research group led by Fungmin Eric Liew of Northwestern University has now increased the bacteria's natural efficiency and technically optimized the process so that the Clostridium cultures produce chemicals such as acetone and isopropanol from CO2. The bacteria do not otherwise produce either substance in nature.
The carbon balance of the process is negative, meaning that the bacteria fix more carbon from the carbon dioxide than they release. This is essential because it is the only way the process can reduce carbon dioxide in the atmosphere. This is not the case with common processes that use bacteria to produce chemical compounds: Typically, sugar is used as a raw material for fermentation processes by bacteria such as E. coli. However, the bottom line is that a lot of greenhouse gas is produced, if only to extract the usable sugars.
Liew and his colleagues had previously optimized Clostridium bacteria so that the germ produces ethanol. Under favorable conditions, the new version of their genetically modified bacterium now secretes significantly more acetone and isopropanol than had previously been possible. Both chemicals are used in industry in much larger quantities; however, their industrial production from gas and oil generates a lot of CO2; this amount of CO2 could be avoided in the future with the genetically modified bacteria. In addition, they could be modified to produce other simple chemical building blocks of industrial importance.
In a commentary accompanying the research article inNature Biotechnology, chemists Corinne D. Scown and Jay D. Keasling calculate how much greenhouse gas could theoretically be saved if all chemicals currently produced from oil or gas for industry were made by carbon-neutral synthetic biological processes. Excluding ammonia, this would produce about one gigaton of CO2 annually. Although this is only about two percent of global greenhouse gas emissions per year, the chemical industry is still the third largest emitter of CO2 after cement production and the steel industry.
Spectrum of Science
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