Thèse Procédés d'Extrusion Réactive pour le Fractionnement et la Valorisation de la Biomasse des Protéines aux Matériaux Biosourcés H/F - Doctorat.Gouv.Fr

Établissement : Université Paris-Saclay GS Sciences de l'ingénierie et des systèmes École doctorale : Interfaces : matériaux, systèmes, usages Laboratoire de recherche : LGPM - Laboratoire de Génie des Procédés et Matériaux Direction de la thèse : Pedro AUGUSTO ORCID 000000017435343X Début de la thèse : 2026-10-01 Date limite de candidature : 2026-05-22T23:59:59 Ce projet de doctorat mettra en oeuvre des procédés d'extrusion réactive pour modifier, fractionner et valoriser des sous-produits agro-industriels, abordant ainsi deux défis majeurs pour l'humanité : l'alimentation et l'environnement. La demande en sources alternatives de protéines ne cesse de croître. Certains sous-produits agro-industriels sont riches en protéines pouvant être utilisées dans l'alimentation, mais il reste à développer un procédé permettant de les extraire efficacement. De plus, le sous-produit restant de cette première extraction, une fraction riche en lignocellulose, doit également être revalorisé pour permettre la valorisation intégrale de cette ressource renouvelable. Bien que les plastiques biosourcés puissent être obtenus à partir de biomolécules raffinées, une approche plus intéressante, mais plus ambitieuse, consiste à les produire à partir de sous-produits agricoles. Ces matériaux ont le potentiel de remplacer les plastiques pétrosourcés, en tant qu'emballages à moindre impact environnemental. Par conséquent, ce projet visera à la fois (1) à développer des procédés d'extrusion réactive pour obtenir des fractions riches en protéines à partir de la biomasse, et (2) à développer des matériaux biosourcés à partir des fractions riches en lignocellulose. Ce projet contribuera ainsi à approfondir les connaissances en ingénierie des procédés appliquées au développement durable. There is a rising demand for alternative sources of proteins, both for food and feed applications, and specifically from plant-based sources. Selected agro-industrial by-products are rich in proteins, such as plant seeds and cakes, or even those obtained after industrial processing, such as brewer's spent grains (BSG). Although the protein content of those materials can reach high values (20-30%d.b.), that biopolymer is entrapped into a lignocellulosic matrix, frequently complexed with other molecules. Its extraction is, therefore, complex, and more efficient, sustainable and cost-effective processes need to be developed to obtain proteins-rich fractions using lesssolvent and energy. Moreover, downstream processing is sometimes required to improve proteins quality for food application, and must also be improved.
After protein extraction, the remaining, secondary by-product, is a lignocellulosic-rich fraction, which needs upcycling for the integral valorisation of the renewable resource. Although bio-based plastics can be obtained from refined biomolecules (such as pure starch or proteins), a more interesting, but challenging approach, is to produce them from agricultural by-products. These materials have the potential to substitute petroleum-based plastics, as packages with lower environmental impact.
Therefore, this PhD Thesis will develop reactive extrusion processes to modify and fractionate agro-industrial by-products, yielding both protein-rich fractions and bio-based materials. The obtained results, processes and products will contribute to the sustainable development by valorising by-products, obtaining new sources of proteins and proposing new sustainable materials.
(1) To develop reactive extrusion processes to fractionate agro-industrial by-products;
(2) To obtain, evaluate and characterize protein-rich fractions, also applying downstream processing strategies to improve their quality for food applications;
(3) To develop, evaluate and characterize bio-based materials from the secondary by-product (lignocellulosic fraction). This PhD Thesis is divided into three parts: (1) prospection of agro-industrial by-products; (2) developing reactive extrusion processes for biomass modification and fractioning, towards the obtention of protein-rich fractions; (3) production and characterization of bio-based materials from the secondary by-product.

Prospection of agro-industrial by-products
Firstly, a prospection of agro-industrial by-products will be carried out, focusing on those with high protein content produced in the Grand Est region of France [1]. For instance, due to their composition and production in the region, brewer's spent grains (BSG), hemp seed cake, grape and apple seeds will be certainly evaluated. Composition and structure will be evaluated, with focus on extruder processability. Consequently, steps such as lipid extraction can be applied to enhance processability.

Developing reactive extrusion processes for biomass modification and fractioning, towards the obtention of protein-rich fractions for food applications
The by-products fractionation process will be developed using reactive extrusion, considered an environmentally friendly process with good scale-up (an approach being already applied by our team in a Horizon Europe project [2]). By combining cooking, mixing and shearing, under pressure with sustainable solvents, both biomass modification and protein extraction will be achieved by using much lower solvent-to-biomass ratio (1-2) compared to traditional extraction (10-20) [3] meanwhile less energy. A multi-criteria optimal configuration will be identified balancing higher protein purity and yield, shorter processing times and reduced energy consumption. The extruder's die will be completed by a filtration module, obtaining a protein-rich liquid fraction and a lignocellulosic-rich solid fraction. Different aqueous solvents for biomass modification and protein extraction will be studied, from the simpler and most used NaOH, to the emerging, but more complex H2O2 [4,5]. The main techno-functional properties of the obtained protein-rich fractions will be evaluated with a focus on food applications. Downstream processing approaches, in special involving membrane technologies, will be applied to increase proteins quality (purity, concentration, bioaccessibility, techno-functional properties).

Production and characterization of bio-based materials from the secondary by-product
After extrusion, the lignocellulosic-rich fraction will be modified and structured in bio-based materials with a focus on plastic applications in packaging.
Although the composition of agro-industrial by-products include molecules with potential for producing the bioplastics (mainly cellulose and starch), a main concern in applying lignocellulosic biomass is the difficult in solubilizing them in the first steps of production. Consequently, different treatments are planned to overcome this challenge. The obtained lignocellulosic biomass will be modified by acid hydrothermal treatment [6-8], using trifluoroacetic [9] or hydrochloric [10] acids. Those processes will be conducted using a twin-screw extruder to perform the hydrothermal treatment at high temperatures, pressures, and shear stresses, potentially reducing the acid concentration and/or treatment time and/or increase efficiency.
The bio-based plastics will be produced by both casting and extrusion techniques [11]. Extrusion will be conducted in a twin-screw extruder, which contains 10 zones of independent temperature control, 3 zones of liquid injection, a zone to recover possibly liquid phase by filtration, as well as the control of pressure and product temperature, powder and product mass flow - similar to applied for biocomposites and materials produced using blend of biopolymers [12,13]. Casting will be conducted by drying the filmogenic solution in a convective oven with control of temperature and humidity. Different surfaces will be evaluated [14].
The plastics will be produced using the by-products, isolated or in combination, water or acid solutions as solvent and other compounds to improve the plastic structure and properties. Glycerol and/or monosaccharides [15] can be used as plasticiser - these can be obtained directly from the by-product processed by acid cooking. Native or modified starches and/or starchy by-products can be used to improve structuration [12,13,16]. Different combinations of lignocellulosic by-product, modification treatments and process conditions will be studied, focusing on obtaining bio-based plastics with different structure and properties, thus targeting possible applications.
The materials will be thoroughly characterized for morphology, water solubility and transport, mechanical properties, thermal properties and transparency. The results will enable to propose possible applications, which will be simulated in comparison with traditional plastics.

Nous recherchons des candidats enthousiastes ayant des connaissances en ingénierie des procédés, en matériaux biosourcés et/ou en bioproduits, de bonnes capacités de communication en anglais (tant à l'oral qu'à l'écrit), une expérience scientifique et la volonté d'apprendre et de s'améliorer.

- This is a two-step selection process. Firstly, a selection process within the research laboratory will be conducted (interview, CV, proposal). Then, the selected candidate will participate in an competition withing the Doctoral School / école doctorale (presentation, proposal, interview, CV).