Missions

One of the initial challenges was maintaining the survival and sulfate-oxidizing function of a pure strain of purple bacteria (Allochromatium vinosum). This challenge was overcome by working under precise physicochemical conditions, in sterile and anoxic environments. The candidate will address the next challenge, which is to precipitate calcium or magnesium carbonates while maintaining the functions of the bacterial strain. They will work on potential changes to the culture medium to optimize the chemical processes involved in carbonate precipitation.

The candidate will be expected to monitor batch or continuous bioreactors to optimize carbonate precipitation while preserving the sulfur-oxidizing activity of the bacteria. These bacteria will be either in pure culture (Allochromatium vinosum) or mixed cultures (with bacteria sampled from wastewater treatment plant waters).

Activités

Preparation of experiments in controlled environments (anoxic and sometimes sterile bottles)
Maintaining the health of bacteria for inoculation
Varying the chemical composition of the bioreactor medium to optimize precipitation (control of the culture medium and gas atmosphere in the reactors)
Monitoring the reactor (sampling and chemical analysis of liquid and solid samples)
Modeling by combining the existing biological model (Aquasim) with precipitation mechanisms (PhreeqC)
Interpreting and presenting results and discussing them in the form of a scientific articles

Compétences

Required Degree: PhD in Environmental Sciences, Biogeochemistry, or Environmental Chemistry
Scientific Skills
Understanding of the carbon cycle and reactions at the water-solid interface

Setup and monitoring of semi-batch bioreactors
Work in anoxic (and sometimes sterile) environments
Assessment of changes in the chemical environment: Ion chromatography, Total Organic Carbon (TOC), Inorganic Carbon (IC), Chemical Oxygen Demand (COD), Atomic Absorption Spectroscopy (AAS)
Characterization of precipitates: TEM, SEM, XRD
Transversal Skills
Autonomy, enthusiasm, curiosity, team spirit, and fluency in English (spoken and written

Contexte de travail

In order to comply with the National Low-Carbon Strategy (SNBC) and the decarbonization targets for energy by 2050, it is necessary to develop energy transformations and production methods that rely on renewable sources of CO₂. These sources may be industrial—through the treatment of flue gases—or biogenic, i.e., derived from biogas. In this context, the CABIOCA project (Biologically Induced Carbonate Precipitation for CO₂ Capture) aims to valorize CO₂ by converting it into mineral forms such as calcium or magnesium carbonates. This transformation of CO₂ into stable (i.e., mineral) carbon can occur naturally through the activity of a range or consortium of bacteria using various metabolic pathways. This process involves increasing the pH of a CO₂-rich (or saturated) environment to induce the precipitation of mineral particles.

Building on existing research and models describing this process in cyanobacteria, the current project proposes to explore the same CO₂ sequestration function using anaerobic phototrophic sulfur bacteria (known as APSB). These bacteria were selected because, in addition to precipitating carbonates using CO₂, they also oxidize reduced sulfur. This dual-function approach offers the advantage of both (a) reducing CO₂ by transforming it into a useful, durable, and stable material, and (b) treating organic carbon and sulfur compound pollution.

Contraintes et risques

There are no physical risks associated with the work. As for so-called “scientific” risks, the following can be mentioned:

The precipitation or its yield may be too low for proper characterization.

Precipitation may be negatively affected by mixed cultures.
To address these issues, work will be conducted to understand the precipitation mechanisms, including identifying limiting factors in order to adapt the culture medium accordingly.

Informations complémentaires

None