Page 34 - Plastics News February 2023

FEATURE

New info on how waste-eating bacteria digest complex carbons could lead to
recycling plastic, plant waste

Most projects to engineer bacteria
involve Escherichia Coli because it is
the most well-studied bacterial model
organism. But E. Coli, in its natural
state, readily consumes various forms
of sugar. As long as sugar is available,
E. Coli will consume that—and leave
the plastic chemicals behind.
“Engineering bacteria for different
purposes is a laborious process,” Aris-
tilde said. “It is important to note that
C. testosteroni cannot use sugars, pe-
riod. It has natural genetic limitations
that prevent competition with sugars,
common environmental bacte- Although other researchers have making this bacterium an attractive
A rium, Comamonas testosteroni, worked to engineer bacteria that can platform.”
could someday become nature’s plas- breakdown plastic waste, Northwest-
tic recycling center. While most bac- ern’s Ludmilla Aristilde believes bac- What C. testosteroni really wants,
teria prefer to eat sugars, C. testos- teria with natural abilities to digest though, is a different source of carbon.
teroni, instead, has a natural appetite plastics hold more promise for large- And materials such as plastic and lignin
for complex waste from plants and scale recycling applications. contain compounds with a ring of
plastics. tasty carbon atoms. While research-
“Soil bacteria provide an untapped, ers have known that C. testosteroni
In a new Northwestern University- underexplored, naturally occurring can digest these compounds, Aristilde
led study, researchers have, for the resource of biochemical reactions and her team wanted to know how.
first time, deciphered the metabolic that could be exploited to help us
mechanisms that enable C. testoster- deal with the accumulating waste on “These are carbon compounds with
oni to digest the seemingly undigest- our planet,” said Aristilde. “We found complex bond chemistry,” Aristilde
ible. This new information could po- that the metabolism of C. testoster- said. “Many bacteria have great diffi-
tentially lead to novel biotechnology oni is regulated on different levels, culty breaking them apart.”
platforms that harness the bacteria to and those levels are integrated. The Combining different ‘omics’
help recycle plastic waste. power of microbiology is amazing and
could play an important role in estab- To study how C. testosteroni de-
The research is published on Feb. grades these complex forms of car-
6 in the journal Nature Chemical lishing a circular economy.” bon, Aristilde and her team com-
Biology. The study was led by Aristilde, an as- bined multiple forms of omics-based
sociate professor of civil and environ- analyses: transcriptomics (study of
Comamonas species are found nearly
everywhere—including in soils and mental engineering at Northwestern’s RNA molecules); proteomics (study
sewage sludge. C. testosteroni first McCormick School of Engineering, of proteins); metabolomics (study of
caught researchers’ attention with and Ph.D. student Rebecca Wilkes, metabolites); and fluxomics (study of
its natural ability to digest synthetic who is the paper’s first author. The metabolic reactions). Comprehen-
laundry detergents. After further study included collaborators from sive multi-omics studies are massive
analysis, scientists discovered that this University of Chicago, Oak Ridge Na- undertakings that require a variety of
natural bacterium also breaks down tional Laboratory and Technical Uni- different techniques. Aristilde leads
compounds from plastic and lignin (fi- versity of Denmark. one of few labs that carries out such
brous, woody waste from plants). Kicking sugar comprehensive studies.

36 PLASTICS NEWS February 2023