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Physicochemical understanding of enzymatically cross-linked casein nanoparticles across the scale
Thesis (PhD)--Stellenbosch University, 2025.
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Stellenbosch : Stellenbosch University
2025
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| _version_ | 1867614083430219776 |
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| access_status_str | Open Access |
| author | Johani, Joshua Tinashe |
| author2 | Lederer, Albena |
| author_browse | Johani, Joshua Tinashe Lederer, Albena |
| author_facet | Lederer, Albena Johani, Joshua Tinashe |
| author_sort | Johani, Joshua Tinashe |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (PhD)--Stellenbosch University, 2025. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/132539 |
| institution | Stellenbosch University (South Africa) |
| last_indexed | 2026-06-10T12:46:23.902Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/132539 Physicochemical understanding of enzymatically cross-linked casein nanoparticles across the scale Johani, Joshua Tinashe Lederer, Albena Stellenbosch University. Faculty of Science. Dept. of Chemistry and Polymer Science. Casein Proteins -- Crosslinking Enzymes Nanoparticles -- Bonding Transglutaminases UCTD Thesis (PhD)--Stellenbosch University, 2025. Johani, J. T. 2025. Physicochemical understanding of enzymatically cross-linked casein nanoparticles across the scale. Unpublished doctoral dissertation. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/d51a93c2-fe55-49a9-a2da-5ebc5ad4dece ENGLISH ABSTRACT: Enzymatic cross-linking for the development of casein-based materials with discrete properties for targeted novel applications as food ingredients, nanocarriers, etc. is attracting interest. Casein is the major protein fraction in milk, consisting of four proteins - αs1-, αs2-, β- and κ-Cn. Casein has an open flexible structure, with some secondary structure elements but lacking of any tertiary structure. It has attracted much attention from scientists because of its propensity to self-associate into nanostructures that are attractive for various applications including the delivery of compounds with therapeutic effects. However, the limitations in application are due to the labile nature of the self-association or dissociation which is influenced by temperature, pH and ionic strength. So far casein has been used as shell material and not discrete particles. Microbial transglutaminase (mTGase) catalyses the formation of lysine-glutamine (K-Q) isopeptide bonds, and has a known preference to cross-link casein molecules that are within distinct particles. It is interesting for controlled cross-linking of casein to generate a variety of sizes and structures of casein nanoparticles with advanced application potential. We established that in salt depleted solution, at approximately neutral pH, casein existed as monomers. In the first part of the study, we applied mTGase to internally cross-link casein so that individual molecules collapsed upon themselves into single chain casein nanoparticles (SCCNP). This is an interesting alternative approach in the field of single chain nanoparticles which has been exclusively based on synthetic polymers to mimic proteins. We employed SDS-PAGE and SEC-D5 for the comprehensive characterisation of the molecular and scaling properties of SCCNPs. Cross-linking mass spectrometry-based proteomics and spectroscopic techniques were applied to localise the isopeptide cross-links, and molecular dynamics simulations were used to correlate findings from the different experimental approaches. In the second part we scaled up the size ranges of casein nanoparticles by incubating varying concentrations of β-NaCn in salt-depleted solution with mTGase. Evolving from single-to-multichain β-NaCn nanoparticles (β-CNP), the molar mass increased with increasing β-NaCn concentration during cross-linking from 25 kg/mol to ~ 500 kg/mol. The dispersity of the β-CNP was lower with increasing enzyme dosage (15-30 U/g), and also with increasing β-NaCn concentration. The β-CNP had spherical conformation with a very dense core. AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar. Doctoral 2025-06-10T14:14:24Z 2025-06-10T14:14:24Z 2025-03 Thesis https://scholar.sun.ac.za/handle/10019.1/132539 Stellenbosch University xiii, 139 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Casein Proteins -- Crosslinking Enzymes Nanoparticles -- Bonding Transglutaminases UCTD Johani, Joshua Tinashe Physicochemical understanding of enzymatically cross-linked casein nanoparticles across the scale |
| title | Physicochemical understanding of enzymatically cross-linked casein nanoparticles across the scale |
| title_full | Physicochemical understanding of enzymatically cross-linked casein nanoparticles across the scale |
| title_fullStr | Physicochemical understanding of enzymatically cross-linked casein nanoparticles across the scale |
| title_full_unstemmed | Physicochemical understanding of enzymatically cross-linked casein nanoparticles across the scale |
| title_short | Physicochemical understanding of enzymatically cross-linked casein nanoparticles across the scale |
| title_sort | physicochemical understanding of enzymatically cross linked casein nanoparticles across the scale |
| topic | Casein Proteins -- Crosslinking Enzymes Nanoparticles -- Bonding Transglutaminases UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/132539 |
| work_keys_str_mv | AT johanijoshuatinashe physicochemicalunderstandingofenzymaticallycrosslinkedcaseinnanoparticlesacrossthescale |