Abstract

The objective of this thesis is to design and study biomimetic materials of the plant primary wall. The primary wall is mainly composed of cellulose microfibrils, pectins and xyloglucan. Families of enzymes modifying the pectin structure have a role in modulating the mechanical properties of the wall and in regulating its growth. However, the mechanisms involved are difficult to analyze in planta and mimetic materials incorporating the main components of the plant cell wall could provide a better understanding of the mechanisms involved.

The first part of the project focuses on the behavior of these materials obtained by casting and rehydrated in order to understand the interactions between polysaccharides and the architecture of the materials. These materials are analogous to gels whose swelling and mechanical properties can be analyzed. The influence of several physicochemical parameters (pH, ionic strength, osmotic pressure) and of the polysaccharide composition on these properties is evaluated.  Then, pectin remodeling enzymes (PME, PG) were applied on the materials to evaluate the impact of this substrate on their behavior and the consequences on the material properties. Finally, a more in-depth study of the mechanical properties was carried out to interpret more precisely the relationships between the complex structure of this composite and its visco-elasto-plastic properties. The results obtained within the framework of the ANR Wallmime are compared to the observations made in planta at the University of Picardie (J. Pelloux's group) and by AFM measurement (A. Boudaoud's group).

Biosourced and biodegradable composite materials whose properties can be modulated by enzymatic way were thus developed.