Semester

Summer

Date of Graduation

2022

Document Type

Dissertation

Degree Type

PhD

College

Statler College of Engineering and Mineral Resources

Department

Chemical and Biomedical Engineering

Committee Chair

Cerasela Zoica Dinu

Committee Co-Chair

Nagasree Garapati

Committee Member

Nagasree Garapati

Committee Member

Jianli Hu

Committee Member

Charter Stinespring

Committee Member

Yuhua Duan

Committee Member

John Twist

Abstract

The specificity and efficiency with which enzymes catalyze selective chemical reactions far exceeds the performance of traditional heterogeneous catalysts that are predominant in industrial applications such as conversion of commodity chemicals to value-added products, fuel cells, and petroleum refinement. Moreover, biocatalysts exhibit exceptionally high product turnover at ambient conditions with little health and environmental burden. These advantageous qualities have led to the prolific use of enzyme catalysis in pharmaceutical, detergents, and food preservation industries wherein their use has greatly reduced waste generation, Unfortunately, the full slate of benefits that enzymes can impart to a broader range of chemical processes is severely hindered by lack of enzyme reusability and/or denaturation of native enzyme structure in industrially relevant conditions, i.e., high temperatures, turbulent flow regimes, non-aqueous solvents.

Enzyme immobilization—the interfacing of biocatalysts with materials possessing properties of interest—is a well-studied strategy to address the shortcomings of free enzyme catalysis. Notably, immobilized enzymes demonstrate improved operability in non-physiological reaction conditions, lengthened shelf lives, and can be separated from reaction mixtures for subsequent reuse. Enzyme immobilization itself is however not a universal solution to the shortcomings that characteristic of free enzyme catalysis. This is because the immobilization of target enzymes often incurs mass transfer limitations, additional costs of materials, and loss of biocatalyst activity that can be prohibitive in the viable implementation. Thus, facile enzyme immobilization techniques require intensive investigation into the interactions between enzymes and carrier/scaffold materials that are not only determinant in the feasibility of immobilized enzymes applications but are also enlightening to the ongoing efforts to establish meaningful relationships between enzyme structure and function that will preserve extended biofunctionality in a variety of synthetic environments.

Herein, we hypothesize that a strategy encompassing both laboratory-scale and computational work should be used to more fully understand the chemical and physical interactions that occur between an immobilized enzyme and different immobilization supports and thereby critically assess the interface between the two can be controlled to develop improved, user-controlled strategies for robust, efficient immobilized biocatalysis.

To demonstrate our hypothesis, we have implemented our strategy on two material systems that are promising in future enzyme immobilization applications. The first material is a hyaluronic acid (HYA)-based polymer network that we have chemically modified to tailor its physicochemical properties for use as an enzyme immobilization platform for biomedical applications. HYA-based hydrogels were synthesized and characterized via techniques like Fourier transform infrared (FTIR) spectroscopy, thermogravimetric (TG) analysis, nuclear magnetic resonance (NMR) spectroscopy, among others; laboratory findings were corroborated with atomistic simulation of our confirmed hydrogel products to understand self-assembly of such polymer networks and how differences in our synthesis protocols impacted polymer properties that are critical in the design of an immobilized enzyme system. The second category of materials that we have investigated is metal-organic framework (MOF)-based composites zeolitic imidazolate framework-8 (ZIF-8) and aluminum (Al)-based MIL-160. The two model MOFs were considered due to their modular, tunable nature which presents a strong opportunity to engineer the interfacial surface at which enzymes interact with such materials and, subsequently, rationally implement optimization strategies that preserve the native structure and function of immobilized enzymes for biocatalytic implementations. Specifically, we have investigated how user-controllable MOF properties—i.e., internal cage structure, hydrophobicity, porosity—impact MOF performance in gas separations and how such properties can be integrated efficiently with active biocatalysts.

Our complex and synergistic findings demonstrate not only the feasibility but rather the necessity of well-designed, user-tailored material interfaces in improving the performance of immobilized enzymes for robust industrial-scale catalysis applications. We expect that the realization of such high-performance technical enzymes will allow for further improvements in the sustainability and economic viability of chemical processes spanning a range of technical sectors.

Embargo Reason

Publication Pending

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