Enzyme Immobilization in Biobased Polymeric Fibrous Matrices for Biocatalytic Textiles: Material Innovation, Mechanistic Studies and Applications

Abstract

This dissertation summarizes our innovation and exploration of a new category of functional material called biocatalytic textiles. The catalytic efficiency of entrapped diffusion limited enzymes in a reaction containing solid, liquid and gas phases is facilitated when dissolved enzyme substrate is transported by liquid flowing through the textile structure. This research is motivated by the challenges existing in global management of CO₂ emissions and recent research on applying biocatalyst (carbonic anhydrase, CA), a class of enzymes that catalyze CO₂ hydration in an ultrafast manner, as an alternative to high energy and high cost traditional liquid solvents in CO₂ scrubbing processes. Therefore, the ultimate goal of this dissertation research is to develop a biocatalytic column packing material with improved enzyme longevity by restraining the enzyme and protecting it from exposure to harsh conditions, through enzyme immobilization and assay development.

Enzyme entrapment is one of the promising methods in enzyme immobilization due to its versatility, high enzyme loading, and mild interactions between the physical supports and enzymes. However, the mass transfer barrier introduced by the entrapment may hinder the overall catalytic efficiency after immobilization, especially when diffusion limited enzymes are entrapped. In order to develop an efficient column packing system with CA enzymes, another diffusion limited enzyme, catalase (CAT) was used as the model enzyme to screen the polymers, fiber formation methods and immobilization approaches in our material innovation. To address the above limitation in enzyme entrapment, with CAT, a robust biocatalytic textile with controllable liquid transport properties is created by coating thin layers of chitosan containing catalase onto a cellulosic yarn. The resulting material integrates enzyme catalytic functionality with protective coating properties of chitosan and structural functionality of the textile, providing a novel and versatile enzyme immobilization strategy. When the material is tested with a flowthrough configuration, it decomposes at least two times more peroxide in a twenty-times smaller reaction zone volume compared to a stirred tank configuration. A constrained wicking mechanism that benefits biocatalytic yarn performance was elucidated by in-situ neutron radiography and neutron computed tomography (CT), from which the liquid transport through the textile structure and liquid spatial distribution within the textile structure were characterized. This CAT immobilized material was then applied to water recycling studies for cotton textile bleaching and dyeing processes, where the immobilized CAT significantly improved the water reusability and decreased the enzyme consumption requirement. Then, the immobilization method was applied to fabricate a lab-scale CO₂ scrubbing packing material with CAs. Without any optimization, the biocatalytic textile has more than twelve times CO₂ absorption compared to a typical Raschig ring packing with lower total weight. To prepare for further characterization of entrapped enzymes in the chitosan layer, this dissertation research also includes a novel biosynthesis of deuterium-labeled chitosan from microorganisms using deuterated glucose in H₂O medium, without the need for conventional chemical deacetylation. After extraction and purification, the chemical composition and structure were determined by Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), and small angle neutron scattering (SANS), providing information about the position of the deuterons in the glucose backbone and changes in the molecular assembly after the deuterium substitution.