PhD in Agricultural Sciences at Laboratoire d’Ingénierie des Biomolécules (LIBio) (France)

Key details

• Host institution: Laboratoire d'Ingénierie des Biomolécules (LIBio)
• Location: Laboratoire d'Ingénierie des Biomolécules (LIBio), NANCY, France
• Application deadline: June 14, 2026

Funding

Not funded by a EU programme

Funding level (from listing): partial or not via EU framework — confirm on the official call.

How to apply

• Application portal / instructions: Official application link.
• Context on Euraxess: Original listing.

About the position

Job Offer: PhD Position at Laboratoire d’Ingénierie des Biomolécules (LIBio)

Project Context and Originality

The development of new systems capable of vectorizing active molecules to a defined target is a major research focus of the Laboratory of Biomolecule Engineering (LIBio). The originality of LIBio lies in the formulation of innovative vectors whose constituents are derived from renewable agro-resources. In this thesis, an original approach based on self-assembly via electrostatic interactions between polyelectrolytes and small ionized biomolecules will be explored.

Interactions between two polyelectrolytes can lead to the formation of various and complex colloidal structures (aggregates, coacervates, soluble complexes, gels, etc.) depending on numerous parameters such as the chemical nature, molecular weight of the species involved, their relative proportions, pH, ionic strength, etc. Many agro-sourced polyelectrolytes, such as polysaccharides and proteins, have proven to be good candidates for forming such structures through liquid-liquid phase separation mechanisms, among others. The interest in these supramolecular assemblies lies in their sensitivity to environmental conditions, allowing control over the formed structures based on the physicochemical properties of the system. It is thus possible to develop assemblies responsive to external parameters such as pH, ionic strength, concentration, temperature, or physical actions like shear stress, opening prospects for controlled release of encapsulated actives.

While the scientific literature is rich in examples of systems composed of two polyelectrolytes (mainly polysaccharides/proteins), it is much less so for systems composed of a polyelectrolyte and smaller charged molecules. This thesis focuses on the study of self-assemblies between polysaccharides and peptides via electrostatic interactions. This work should open a new research avenue in the development of agro-sourced colloidal systems reactive to external stimuli and potential vectors for active molecules. The polysaccharides considered are chitosan and gum arabic, well-known substrates at LIBio, acting as a polycation and polyanion, respectively. The peptides will either be commercial or derived from parallel projects within partner laboratories of the Biomolecules 4 Bioeconomy (B4B) project, of which LIBio is an integral part.

Scientific Questions

• What colloidal structures spontaneously form through electrostatic interactions between macromolecules and peptides?
• Is it possible to modulate these structures based on the physicochemical parameters of the medium (pH, ionic strength, temperature)?
• Can the formed structures be used for the encapsulation and controlled release of active biomolecules regardless of their properties?

This thesis will begin with a bibliographic review of systems formed by electrostatic interactions between charged molecules derived from agro-resources, particularly polysaccharides. The choice of polysaccharides is fixed (chitosan and gum arabic), but the peptides will be selected based on the literature and intra- or inter-laboratory collaborations. Initial experiments will involve the simple mixing of aqueous solutions of a polysaccharide and a peptide (or a mixture of peptides). If turbidity is observed, characterization of the formed objects will be carried out using optical and/or electron microscopy, depending on their size, and light scattering (dynamic or static). Isothermal titration calorimetry experiments will be conducted to define the associated thermodynamic parameters. The stability of the formed colloidal structures will also be monitored using static multiple light scattering. Finally, modifications of the physicochemical conditions will highlight the system’s response to external stimuli.

It will also be possible to test ternary systems using the same methods to address the question: What is the impact of adding a charged molecule (polymer or peptide) to preexisting electrostatic assemblies? For example, adding a peptide to a chitosan/gum arabic assembly (coacervate or soluble complex, mastered at LIBio) may lead to structural changes at the colloidal scale. Depending on the progress of the thesis, numerous systems can be explored to rationalize the formed structures based on the associated chemical and physicochemical parameters.

Experimental Approaches

The experimental methods will focus on:

• Titration techniques (turbidimetry, isothermal titration calorimetry);
• Colloidal stability studies (static multiple light scattering, turbidimetry);
• Particle size and charge measurements (dynamic light scattering, laser granulometry);
• Nanoscale structural characterization (small-angle X-ray scattering [SAXS], access to the SOLEIL synchrotron [SWING beamline]).

Modification of polysaccharides via enzymatic or chemical routes (mastered at LIBio) is also possible to alter their chemical groups, enabling modulation of interactions with other biomolecules.

Future Perspectives

Encapsulation or purification applications will be tested at the end of the thesis, depending on results.

Candidate Profile

The candidate must hold a Master’s degree (BAC+5) in physical chemistry or biochemistry with experience in:

• Peptides (extraction, purification, characterization),
• Polyelectrolytes,
• Colloidal systems.

They should have a strong affinity for laboratory work and be able to integrate well into a research team.

Keywords

Colloids, polysaccharides, peptides, interactions, coacervation

Required/Developed Skills During the PhD

• Peptide characterization (chromatographic methods, LC-MS/MS);
• Biopolymer characterization (Fourier-transform infrared spectroscopy, size-exclusion chromatography, nuclear magnetic resonance);
• Characterization of nano- and micro-objects (size, structure, charge);
• Thermodynamic parameters of interactions;
• Small angle scattering (SAXS).

Additional Information

Website of the laboratory: http://libio.univ-lorraine.fr/

Website of the Université de Lorraine: https://www.univ-lorraine.fr/

Laboratory located in Nancy, Grand EST region (1h30 of Paris by train), France: https://www.nancy.fr/

Funding category: Contrat doctoral

PHD title: Doctorat en Génie biotechnologique et alimentaire

PHD Country: France