Cyanobacteria as 'green' catalysts in biotechnology

Date:
October 5, 2020
Source:
Graz University of Technology
Summary:
Researchers show how the catalytic activity of cyanobacteria, also
known as blue-green algae, can be significantly increased. This
brings biotechnological and thus eco-friendly application a big
step closer.



FULL STORY ========================================================================== Cyanobacteria, despite staining water green through their special
pigments, are colloquially known as "blue-green algae," and convert
light energy into chemical energy particularly effectively thanks to
their highly active photosynthetic cells. This makes them attractive for biotechnological application, where they could be used as environmentally friendly and readily available biocatalysts for the production of new
chemicals using specifically introduced enzymes.


========================================================================== Limited light availability What sounds good in theory, is still facing obstacles in the practical large- scale technological implementation. A decisive limiting factor is currently the availability of light, as Robert Kourist from the Institute of Molecular Biotechnology at Graz University
of Technology explains: "When cyanobacteria are densely grown, i.e. in
high concentrations, only the cells located on the outside receive enough light. Inside it's pretty dark. This means that the amount of catalyst
cannot be increased at will. After a cell density of a few grams per
litre, the photosynthetic activity and thus the productivity of the
cells decreases sharply. This is of course a considerable disadvantage
for large-scale biotechnological production." By comparison, previously established biocatalysts such as yeasts can be used with cell densities
of 50 grams per litre and more. The established production organisms
have the major disadvantage that they depend on agricultural products
as a basis for growth and thus consume many resources. "Algae-based
catalysts can be grown from water and CO2, so they are 'green' in a
two-fold sense. For this reason, intensive efforts are under way to
increase the catalytic performance of cyanobacteria," said Kourist.

Making better use of available light Together with Ruhr University Bochum
and the Finnish University of Turku, the algae working group at TU Graz
has now succeeded in increasing precisely this catalytic performance by specifically redirecting the photosynthetic electron flow to the desired catalytic function. "For the first time, we were able to measure the
supply of photosynthetic energy directly in the cells in a time- resolved manner so that we were able to identify bottlenecks in the metabolism," explains Marc Nowaczyk from the Chair of Plant Biochemistry at the Ruhr University Bochum.

"We have switched off a system in the genome of the cyanobacterium that
is supposed to protect the cell from fluctuating light. This system is
not necessary under controlled cultivation conditions, but consumes photosynthetic energy. Energy that we prefer to put into the target
reaction," explains Hanna Bu"chsenschu"tz, doctoral student at TU Graz and first author of the study. In this way, the problem of low productivity
of cyanobacteria due to high cell densities can be solved. "To put
it another way, we can only use a certain amount of cells. That's why
we have to make the cells go faster. We have developed a method using
so-called metabolic engineering that makes cyanobacteria a great deal
more mature for biotechnological application," said Kourist.

In addition to increasing the productivity of the cell itself through
targeted interventions at the gene level, the Graz researchers are also
working on new concepts for the algae cultivation process. One approach is
to introduce light sources directly into the cell suspension, for example
via mini LEDs. New geometries are also being experimented with. Thus, cyanobacteria in the form of encapsulated small spheres, so-called
"beads," can absorb more light overall.

Robert Kourist comments: "It is very important to develop all measures on
the way to large-scale industrial application of algae-based biocatalysts
in an integrated way. This is only possible with interdisciplinary
research that looks at the function of an enzyme in the same way as we
look at engineering in the photosynthetic cell."

========================================================================== Story Source: Materials provided by
Graz_University_of_Technology. Original written by Susanne Eigner. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Leen Assil-Companioni, Hanna C. Bu"chsenschu"tz, Da'niel Solymosi,
Nina
G. Dyczmons-Nowaczyk, Kristin K. F. Bauer, Silvia Wallner, Peter
Macheroux, Yagut Allahverdiyeva, Marc M. Nowaczyk, Robert Kourist.

Engineering of NADPH Supply Boosts Photosynthesis-Driven
Biotransformations. ACS Catalysis, 2020; 11864 DOI: 10.1021/
acscatal.0c02601 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/10/201005101532.htm

--- up 6 weeks, 6 hours, 50 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1337:3/111)