Light-powered microbes are super-producing chemical factories
Date:
April 11, 2022
Source:
Osaka University
Summary:
Researchers have found that engineering the light-dependent proton
pump rhodopsin into Escherichia coli redirects carbon flow from
cellular metabolism to biosynthetic product generation. This
approach of using light as an energy source can help improve the
efficiency of target compound production and reduce CO2 emissions.
FULL STORY ========================================================================== Sharing is key to living in society, whether it's toddlers sharing toys
or nations sharing natural resources; but there's no avoiding the fact
that one side getting more means that the other side gets less. Now, researchers from Osaka University, in collaboration with the University
of Shizuoka and Kobe University, have found a way to get around the need
for sharing energy in biomanufacturing, so that the cellular pathways
dedicated to generating the product always get more.
==========================================================================
In a study published recently in Metabolic Engineering, the researchers
have revealed that microorganisms can be engineered to use light for
energy, freeing up cellular resources to produce biomanufactured products.
Metabolically engineered microorganisms are used to produce various
useful chemicals throughout the world, but there's a catch: both microbial growth and chemical synthesis require a molecule called ATP as an energy source. Because of this, keeping the cellular "factories" healthy limits chemical production.
"Microorganisms that produce useful substances are usually developed
by modifying metabolism to convert energy that would normally be used
for growth into a resource for synthesizing these target substances,"
explains Yoshihiro Toya, first author on the study. "We reasoned that
instead we could use light, an external energy source, to improve
production of useful substances without disrupting the microorganisms'
natural metabolism." To test this, the researchers introduced a
heterologous membrane protein called rhodopsin into Escherichia coli,
a common microorganism used in biomanufacturing. Rhodopsin is a pump
that is activated by light, and the action of the pump leads to the
generation of ATP without using the cell's natural machinery (known as
the TCA cycle and respiratory chain) to produce it.
This approach has the added benefit of reducing the emission of carbon
dioxide, a byproduct of the TCA cycle.
"The results clearly showed the success of our strategy," states
Kiyotaka Y.
Hara, project leader. "The cells expressing rhodopsin generated
significantly more chemical products when exposed to light, and the
carbon flow in these cells was directed away from energy generation
and toward chemical synthesis." Once they had proved that this concept
worked for various compounds such as 3- hydroxypropionate, mevalonate,
and glutathione, the researchers went on to create three new strains
of E. coli. One of these strains expressed super- rhodopsins with even
better pump activities than the original rhodopsin that was tested;
this strain was developed by Dr Toya's group at Osaka University.
The other two strains incorporated synthetic biological systems that
provided an intrinsic supply of retinal, the activator of rhodopsin,
and optimized the balanced expression of multiple genes in the relevant metabolic pathway; these strains were established by Dr Jun Ishii's
group at Kobe University. Finally, Dr Hara's group at the University
of Shizuoka integrated all of these systems into a single E. colistrain
that produces a chemical in a light-dependent manner.
"Our findings suggest that biomanufactured microorganisms designed to
use light for energy source can be used to efficiently biosynthesize
useful target compounds," states Hara.
This new approach is expected to increase the efficiency of producing
useful materials through fermentation and other bioprocesses while simultaneously reducing carbon emissions.
========================================================================== Story Source: Materials provided by Osaka_University. Note: Content may
be edited for style and length.
========================================================================== Journal Reference:
1. Yoshihiro Toya, Yoko Hirono-Hara, Hidenobu Hirayama, Kentaro
Kamata, Ryo
Tanaka, Mikoto Sano, Sayaka Kitamura, Kensuke Otsuka, Rei
Abe-Yoshizumi, Satoshi P. Tsunoda, Hiroshi Kikukawa, Hideki
Kandori, Hiroshi Shimizu, Fumio Matsuda, Jun Ishii, Kiyotaka
Y. Hara. Optogenetic reprogramming of carbon metabolism using
light-powering microbial proton pump systems.
Metabolic Engineering, 2022; 72: 227 DOI:
10.1016/j.ymben.2022.03.012 ==========================================================================
Link to news story:
https://www.sciencedaily.com/releases/2022/04/220411101331.htm
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