Public defence in Bioproduct Technology, M.Sc. (Tech.) Ville Rissanen
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Title of the thesis: Development of Leaf-Inspired Functional Structures from Cellulose Nanofibers - Matrix Scaffolds for Solid-State Photosynthetic Cell Factories
Doctoral student: M.Sc. (Tech.) Ville Rissanen
Opponent: Professor Lars Berglund, KTH Royal Institute of Technology, Sweden
Custos: Professor Eero Kontturi, Aalto-yliopiston School of Chemical Engineering, Department of Bioproducts and Biosystems
Development of Leaf-Inspired Functional Structures from Cellulose Nanofibers - Matrix Scaffolds for Solid-State Photosynthetic Cell Factories
The aim of this thesis was to prepare and investigate leaf-inspired hydrogel structures from cellulose nanofibers (CNF) that act as a matrix for immobilizing photosynthetic microbes. The overall objective was to create life-sustaining matrix structures with high mechanical stability, porosity and biological compatibility, and to assess how these properties can be reliably measured and linked to the viability and biological performance of the photosynthetic cells. Ultimately, the target was to create photosynthetic cell factory platforms, where the immobilized cells can produce volatile chemicals. From a broader perspective, the work attempts to create a toolbox using biomaterials technology and combine it with synthetic biology and algae biotechnology to gain a more holistic understanding on how to optimize the efficiency of such unique production systems. The thesis adapted methods based on rheology, surface-sensitive analytics and thermoporosimetry to identify and investigate the most relevant properties of the CNF -based matrices. It was found that TEMPO-oxidized cellulose nanofibers provided strong and highly biocompatible matrix structures when cross-linked with polyvinyl alcohol and Ca2+-ions. In comparison to the conventional cell immobilization material, alginate, the CNF-based matrices were found more resistant to yielding under stress. They also possessed higher porosity but a more heterogeneous pore structure. In biological assessments both matrix types were observed to provide long-term cell viability to immobilized cells over 9 weeks, but CNF -based matrices were shown to be more stable and enable higher hydrogen and ethylene production in submerged conditions. Interestingly, gas exchange results indicated that both the cells and the matrices undergo dynamic changes over time that are affected by the rheology and porosity of the matrix structures. To gain improved control over these properties, a method to prepare CNF hydrogels with accurate porosity and density was developed using osmotic dehydration. Overall, these findings highlight the prowess of TCNF-based hydrogels as versatile immobilization scaffolds and showcase how the development of efficient cell factory platforms can be assisted via interdisciplinary efforts.
Thesis available for public display 10 days prior to the defence
Contact information:
M.Sc. (Tech.) Ville Rissanen
ville.rissanen@vtt.fi
Doctoral theses in the School of Chemical Engineering