Bacteria as climate heroes

Date:
November 17, 2021
Source:
Vienna University of Technology
Summary:
Acetogens are a group of bacteria that can metabolise formate. For
example, they form acetic acid -- an important basic chemical. If
these bacteria were manipulated to produce ethanol or lactic acid,
a comprehensive circular economy for the greenhouse gas CO2 could
be realised. To ensure that the process is sustainable, the CO2
is extracted directly from the air and converted to formate using
renewable energy. To find out how exactly formate can be utilised
by the Acetobacterium woodii (short: A. woodii), a team led by
Stefan Pflu"gl from the Institute of Chemical, Environmental and
Bioscience Engineering at TU Wien investigated how the bacterium
metabolises various substrates - - including formate. Furthermore,
the researchers used a metabolic model to study how A. woodii
could be genetically modified to produce substances other than
acetic acid.



FULL STORY ========================================================================== Acetogens are a group of bacteria that can metabolise formate. For
example, they form acetic acid -- an important basic chemical. If
these bacteria were manipulated to produce ethanol or lactic acid,
a comprehensive circular economy for the greenhouse gas CO2 could be
realised. To ensure that the process is sustainable, the CO2 is extracted directly from the air and converted to formate using renewable energy.


========================================================================== Circular economy for CO2 "The economy of the future must be carbon
neutral," demands Stefan Pflu"gl.

However, since carbon is an important component of many products --
such as fuel or plastics -- the existing CO2 should be recycled and
returned to the cycle. One climate-neutral way to do this is capture
CO2 directly from the air and convert it into formate with the help
of renewable energy. This compound of carbon, oxygen and hydrogen can ultimately be a basic building block of the bioeconomy. The advantages
of formate are that it is easy to transport and can be used flexibly for
the production of chemicals and fuels. These substances can be produced
with the help of acetogenic bacteria that feed on carbon compounds and
produce acetic acid from them.

Formate recycling by A. woodii In order to use acetogens for the
production of raw materials, one needs to understand their metabolism
and physiology. Although A. woodii is a model organism, meaning that the bacterium has already been extensively studied, the research team wanted
to make a comparative observation. Thus, Stefan Pflu"gl and his team investigated how substrates such as formate, hydrogen, carbon monoxide,
carbon dioxide or fructose affect the metabolism of A. woodii.

"The biggest difference, caused by the different substrates, is the amount
of energy that A. woodii gains," observes Stefan Pflu"gl. He explains
this as follows: "Acetogens are true survival artists that can also
metabolise substrates such as CO, CO2 or formate. This is due to the
fact that acetogens use what is probably the oldest metabolic pathway
for CO2 fixation. Thus, they also manage to produce enough energy to
survive under extreme conditions and from alternative food sources."
This means that acetogens are not only able to utilise CO2 but also
do so very efficiently. Consequently, only little energy needs to be
expended to convert CO2 into formate, which is then converted into the
basic chemical acetic acid.

Replacement of oil-based products To exploit the full potential of
A. woodii, the researchers also investigated how the bacterium can be genetically modified to produce ethanol or lactic acid instead of acetic
acid. While ethanol forms the basis for fuel, lactic acid can be used to produce biodegradable plastics. Oil-based substances could consequently
be replaced by more sustainable alternatives. "Not only would this be
in the sense of the bioeconomy, but CO2 and carbon monoxide, which are
produced during the combustion of fuel or plastic, could also be recycled
to the original product," Stefan Pflu"gl envisages.

The study, which has been published in the journal Metabolic Engineering,
thus provides insights into what acetogens like A. woodii can do under
certain conditions. Based on the experimental data and using a model,
the researchers also developed strategies on how A. woodii can be
genetically manipulated and used for the production of other substances.

========================================================================== Story Source: Materials provided by Vienna_University_of_Technology. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Christian Simon Neuendorf, Gabriel A. Vignolle, Christian Derntl,
Tamara
Tomin, Katharina Novak, Robert L. Mach, Ruth Birner-Gru"nberger,
Stefan Pflu"gl. A quantitative metabolic analysis reveals
Acetobacterium woodii as a flexible and robust host for
formate-based bioproduction. Metabolic Engineering, 2021; 68:
68 DOI: 10.1016/j.ymben.2021.09.004 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/11/211117100133.htm

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