Description du projet :
Polyhydroxyalkanoates (PHA) are polyesters naturally accumulated by prokaryotes as
carbon and energy storage in the form of intracellular granules. Apart from their
crucial biological roles, they represent promising, sustainable and biodegradable
alternatives to petrochemical polymers. To study their biosynthesis, we focus on the
bacterium Rhodospirillum rubrum for its extraordinary metabolic flexibility, which
designates it as a perfect model organism, representative of many PHA-producing
bacteria with diverse biosynthetic strategies. At the very basis of bacterial PHA
biosynthesis and mobilization lies the so-called PHA cycle, based on pivotal enzymes:
PHA synthase and PHA depolymerase. It is our main objective to unravel the complex
modulation pathways of the activity of these enzymes as a means to rationalize the link
between cultivation conditions, cell PHA content, and also production rate. We will
eventually propose a model for PHA cycle dynamics based on the data accumulated in
order to predict PHA accumulation as a function of the environmental conditions.
In the course of this study, the role of PHA in the bacterial energy household will be
characterized and quantified for various metabolic pathways in fermentations and the
effects of cell memory from cultivation history will be examined in a way to identify
supplementary factors affecting bacterial responses in terms of PHA production. After
their purification, we will measure the activity of the enzymes in vitro, determine the
effects of various factors affecting their activity (e.g. pH, nature of substrate, phasins)
and unfold their interplay within the PHA cycle. Furthermore, the study will be
extended to the assessment of the different biological roles of PHA granules in the
bacterium, especially in terms of resistance against environmentally and
biotechnologically relevant stress factors.
Besides building on advanced cultivation cultures, such as two stage continuous
cultures, gas fermentation, photo-bioprocesses, we will harness tools from
bioinformatics and metabolomics for characterizing the dynamics of the PHA cycle. In
particular, the transcriptomic analyses under various cultivation conditions will be on
focus. This will be complemented with a multitude of biophysical characterization
techniques for bacterial state, granule number, shape and properties, as well as
polymer composition and molecular weight characterization. As an ultimate level of
analysis and understanding, modeling and simulation will be deployed, on the basis of
the data collected, and coupled with experimental validation.
This battery of complementary techniques is expected to provide the multi-dimensional
perspective necessary to unravel the complex PHA dynamics and its regulation
mechanisms and. The gained knowledge can be extended to the control of PHA
accumulation rates and its composition.
This project represents an outstanding opportunity for both partners of the consortium
to express together their strong expertise in the subject of PHA biosynthesis. Their
shared knowledge, competences, and know-how will bring the understanding of PHA
biosynthesis metabolism to a higher level. This will ultimately enable to further design
and optimize suitable systems for PHA production, contributing to the deployment of
some of the most promising future bioplastic materials, and therefore to a significantly
decreased environmental impact of human activities.
Research team within HES-SO:
Zinn Manfred
, Amstutz Véronique
, Ochsner Andrea Maria
, Fleuriot-Blitman Hugo
Partenaires académiques: Prof. Stanislav Obruca, Brno University of Technology, Brno, Czech Republic
Durée du projet:
01.01.2021 - 31.12.2023
Statut: Ongoing
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