Project Details
Projekt
Enzymatic cross-linking of casein nanoparticles across the scales: Fundamental mechanisms and technological potentials
Subject Area
Biological Process Engineering
Term
since 2015
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 281461845
Transglutaminase is an enzyme that catalyses the formation of isopeptide bonds between protein bound glutamine and lysine residues and therefore the polymerisation of single protein molecules. In the food sector, transglutaminase of microbial origin (mTGase) is used in the meat and fish industry, for instance for ham and surimi production. Other reported applications refer to milk proteins, as casein represents an excellent substrate for the enzyme. In a recently completed joint project the applicants demonstrated that the action of mTGase on casein molecules, which are non-covalently associated to nanoparticles, results in the formation of intra-particle cross-links. This leads to a fixation of the molecules and significant changes in the shape and density of the particles. Cross-linking intensity itself depends on environmental factors, including for example ionic strength of the substrate. With the proposed project we aim for a broadening of the range of particle sizes that can be obtained from cross-linking with mTGase by varying additional factors. We will analyse the molecular and colloidal properties of the differently sized nanoparticles, and demonstrate their application potential by using two prominent examples.On the basis of our latest results we build the hypothesis that the self-association of non-micellar casein to hydrated nanoparticles, driven by concentration, ionic strength and by temperature, enables us to fixate and modify their conformation and to create differently sized nanoparticles with a great potential for selected applications. In the first of four workpackages, we will systematically vary the casein concentration and dissolution parameters to identify conditions at which the casein monomers are available for intramolecular cross-linking to single-chain casein nanoparticles and, on the other hand, conditions where casein particles are so closely packed that interparticle cross-linking is facilitated. After finishing WP 1, the incubation conditions for controlled preparation of casein nanoparticles at different scales are identified, and samples for the following research steps are prepared. Two subsequent workpackages are dedicated to the in-depth analysis of the molecular and the colloidal properties of the resulting nanoparticles using techniques already established during our previous cooperation (e.g., AF4-MALS, suspension rheology), but also by developing new approaches (e.g., surface plasmon resonance spectroscopy, interfacial rheology). These analyses will help to understand structure-function relationships and are, in a concluding workpackage, complemented by the evaluation of potential applications of cross-linked caseins, e.g., as nanocarriers or as stabilisers in Pickering emulsions.
DFG Programme
Research Grants
Co-Investigators
Dr. Susanne Boye; Dr.-Ing. Doris Jaros
