Microbes working together multiply biomass conversion possibilities


Date:
August 27, 2020
Source:
Ecole Polytechnique Fe'de'rale de Lausanne
Summary:
Non-edible plants are a promising alternative to crude oil, but
their heterogenous composition can be a challenge to producing high
yields of useful products. Scientists have developed a platform
that combines different microorganisms that can make a dramatic
difference.



FULL STORY ==========================================================================
With the race for renewable energy sources in full swing, plants offer one
of the most promising candidates for replacing crude oil. Lignocellulose
in particular -- biomass from non-edible plants like grass, leaves, and
wood that don't compete with food crops -- is abundant and renewable
and offers a great alternative source to petroleum for a whole range
of chemicals.


==========================================================================
In order to extract useful chemicals from it, lignocellulose is first pretreated to "break it up" and make it easier to further process. Then
it's exposed to enzymes that solubilize cellulose, which is a chain
of linked up sugars (glucose). This step can be done by adding to the pre-treated lignocellulose a microorganism that naturally produces the necessary, cellulose-cleaving enzymes, e.g. a fungus.

The enzymes "crack" the cellulose and turn it into its individual
sugars, which can be further processed to produce a key chemical:
lactic acid. This second step is also accomplished with a microorganism,
a bacterium that "eats" the sugars and produces lactic acid when there's
no oxygen around.

In the final step of this microbial assembly line, the lactic acid can
then be processed to make a whole host of useful chemicals.

A team of scientists from the Bern University of Applied Sciences (BFH),
the University of Cambridge, and EPFL have made this assembly chain
possible in a single setup and demonstrated this conversion can be made
more versatile and modular. By easily swapping out the microorganisms
in the final, lactic-acid processing, step, they can produce a whole
range of useful chemicals.

The breakthrough study is published in Science, and was carried out by
Robert Shahab, an EPFL PhD student in Professor Jeremy Luterbacher's
lab, while working at the lab of Professor Michael Studer at the BFH,
who led the study.



==========================================================================
The researchers present what they refer to as a "lactate platform,"
which is essentially a spatially segregated bioreactor that allows
multiple different microorganisms to co-exist, each performing one of
the three steps of lignocellulose processing.

The platform consists of a tubular membrane that lets a defined amount of oxygen to go through it. On the tube's surface can be grown the fungus
that consumes all oxygen that passes through the membrane, and provides
the enzymes that will break up cellulose into sugars. Further away from
the membrane, and therefore in an atmosphere without oxygen, grow the
bacteria that will "eat" the sugars and turn them into lactic acid.

But the innovation that Shahab made was in the last step. By using
different lactic acid-fermenting microorganisms, he was able to produce different useful chemicals. One example was butyric acid, which can be
used in bioplastics, while Luterbacher's lab recently showed that it
can even be turned into a jet fuel.

The work demonstrates the benefits of mixed microbial cultures in lignocellulose biomass processing: modularity and the ability to convert complex substrates to valuable platform chemicals.

"The results achieved with the lactate platform nicely show the
advantages of artificial microbial consortia to form new products from lignocellulose," says Michael Studer. "The creation of niches in otherwise homogeneous bioreactors is a valuable tool to co-cultivate different microorganisms." "Fermenting lignocellulose to a lot of different
products was a significant amount of work but it was important to show
how versatile the lactate platform is," says Robert Shahab. "To see the formation of lactate and the conversion into target products was a great experience as it showed that the concept of the lactate platform worked
in practice." Jeremy Luterbacher adds: "The ultimate goal is to rebuild
a green manufacturing sector to replace one that produces many products
from crude oil. A method that introduces flexibility and modularity is
an important step in that direction."

========================================================================== Story Source: Materials provided by
Ecole_Polytechnique_Fe'de'rale_de_Lausanne. Original written by Nik Papageorgiou. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Robert L. Shahab, Simone Brethauer, Matthew P. Davey, Alison
G. Smith,
Silvia Vignolini, Jeremy S. Luterbacher, Michael H. Studer. A
heterogeneous microbial consortium producing short-chain fatty
acids from lignocellulose. Science, 2020; 369 (6507): eabb1214 DOI:
10.1126/ science.abb1214 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200827141331.htm

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