A new method for making a key component of plastics

Date:
August 27, 2020
Source:
Ohio State University
Summary:
Scientists have discovered a previously unknown way that some
bacteria produce the chemical ethylene - a finding that could lead
to new ways to produce plastics without using fossil fuels. The
study showed that the bacteria created ethylene gas as a byproduct
of metabolizing sulfur, which they need to survive.



FULL STORY ========================================================================== Scientists have discovered a previously unknown way that some bacteria
produce the chemical ethylene -- a finding that could lead to new ways
to produce plastics without using fossil fuels.


==========================================================================
The study, published today (Aug. 27, 2020) in the journal Science, showed
that the bacteria created ethylene gas as a byproduct of metabolizing
sulfur, which they need to survive.

But the process that the bacteria use to do that could make it very
valuable in manufacturing, said Justin North, lead author of the study
and a research scientist in microbiology at The Ohio State University.

"We may have cracked a major technological barrier to producing a large
amount of ethylene gas that could replace fossil fuel sources in making plastics," North said.

"There's still a lot of work to do to develop these strains of bacteria
to produce industrially significant quantities of ethylene gas. But this
opens the door." Researchers from Ohio State worked on the study with colleagues from Colorado State University, Oak Ridge National Laboratory
and the Pacific Northwest National Laboratory.



========================================================================== Ethylene is widely used in the chemical industry to make nearly all
plastics, North said. It is used more than any other organic compound
in manufacturing.

Currently, oil or natural gas are used to create ethylene. Other
researchers have discovered bacteria that can also create the chemical,
but there had been a technological barrier to using it -- the need for
oxygen as part of the process, said Robert Tabita, senior author of the
study and professor of microbiology at Ohio State.

"Oxygen plus ethylene is explosive, and that is a major hurdle for using
it in manufacturing," said Tabita, who is an Ohio Eminent Scholar.

"But the bacterial system we discovered to produce ethylene works
without oxygen and that gives us a significant technological advantage."
The discovery was made in Tabita's lab at Ohio State when researchers were studying Rhodospirillum rubrum bacteria. They noticed that the bacteria
were acquiring the sulfur they needed to grow from methylthio ethanol.



==========================================================================
"We were trying to understand how the bacteria were doing this, because
there were no known chemical reactions for how this was occurring,"
North said.

That was when he decided to see what gases the bacteria were producing --
and discovered ethylene gas was among them.

Working with colleagues from Colorado State and the two national labs,
North, Tabita and other Ohio State colleagues were able to identify the previously unknown process that liberated the sulfur the bacteria needed,
along with what North called the "happy byproduct" of ethylene.

That wasn't all: The researchers also discovered the bacteria were using dimethyl sulfide to create methane, a potent greenhouse gas.

All the research was done in the lab, so it remains to be seen exactly
how common this process is in the environment, North said.

But the researchers have identified one situation where this newly
discovered process of ethylene production may have real-life consequences.

Ethylene is an important natural plant hormone that, in the right amounts,
is key to the growth and health of plants. But it is also harmful to
plant growth in high quantities, said study co-author Kelly Wrighton,
associate professor of soil and crop science at Colorado State University.

"This newly discovered pathway may shed light on many previously
unexplained environmental phenomena, including the large amounts of
ethylene that accumulates to inhibitory levels in waterlogged soils,
causing extensive crop damage," Wrighton said.

Added North: "Now that we know how it happens, we may be able to
circumvent or treat these problems so that ethylene doesn't accumulate
in soils when flooding occurs." Tabita said this research is the result
of a happy accident.

"This study, involving the collaborative research and expertise of two universities and two national laboratories, is a perfect example of how serendipitous findings often lead to important advances," Tabita said.

"Initially, our studies involved a totally unrelated research problem
that had seemingly no relationship to the findings reported here."
While studying the role of one particular protein in bacteria sulfur metabolism, the researchers noted an entirely different group of proteins
were unexpectedly involved as well. This led to the discovery of novel metabolic reactions and the unexpected production of large quantities
of ethylene.

"It was a result we could not predict in a million years," Tabita said.

"Recognizing the industrial and environmental significance of ethylene,
we embarked on these cooperative studies, and subsequently discovered a completely novel complex enzyme system. Who would have believed it?" The research was supported by the Department of Energy's Office of Science,
the National Cancer Institute and the National Science Foundation.


========================================================================== Story Source: Materials provided by Ohio_State_University. Original
written by Jeff Grabmeier. Note: Content may be edited for style and
length.


========================================================================== Journal Reference:
1. Justin A. North, Adrienne B. Narrowe, Weili Xiong, Kathryn
M. Byerly,
Guanqi Zhao, Sarah J. Young, Srividya Murali, John A. Wildenthal,
William R. Cannon, Kelly C. Wrighton, Robert L. Hettich,
F. Robert Tabita. A nitrogenase-like enzyme system catalyzes
methionine, ethylene, and methane biogenesis. Science, 2020 DOI:
10.1126/science.abb6310 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200827141303.htm

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