2024 AIChE Annual Meeting

(4gm) Advancing Biomanufacturing for Defossilization of the Carbon Economy

Author

Lee, S. H. - Presenter, Rice University
Phasing out fossil fuels presents a formidable challenge as the global economy heavily relies on them. While the energy sector is shifting towards carbon-free sources like solar and wind power, sectors such as agriculture, liquid fuels, chemicals, and textiles remain dependent on carbon, essential for their processes. Achieving a "defossilized" carbon economy requires efficient utilization of waste carbon sources alongside sustainable energy solutions with minimal environmental impact. My passion lies in leveraging enzymes, organisms, and biochemical processes to replace fossil fuels across the entire carbon economy spectrum, spanning agriculture, energy, chemicals, and materials. Central to this goal is diversifying biomanufacturing feedstocks to incorporate cheaper, more sustainable alternatives. Furthermore, enhancing current performance metrics—typically assessed by titer, rate, and yield (TRY)—is crucial to meet industry standards for commercialization. Finally, addressing scalability challenges in fermentation processes, which often exhibit inconsistent performance at different scales, is imperative to instill confidence among researchers and funders in biomanufacturing's potential.

Research Interests

Aim 1: Engineering synthetic metabolic pathways into non-model microbes

My expertise centers on optimizing synthetic pathways for diverse product synthesis. I plan to advance these pathways beyond E. coli, leveraging yeasts and non-model bacteria to enhance carbon efficiency and broaden product profiles. Implementing the Formyl-CoA Elongation (FORCE) pathway in Komagataella phaffii shows promise for methanol utilization, overcoming toxicity and low productivity issues seen in E. coli. Adapting the reverse beta-oxidation (rBOX) cycle in acetogens like Eubacterium limosum aims to expand their product range efficiently. C-C coupling enzymes like HACS and thiolase from these pathways are crucial for biopolymer synthesis. Streamlining pathways in organisms like Cupriavidus necator can enhance efficiency in producing polyhydroxyalkanoates (PHAs).

Aim 2: Carbon and energy-efficient product synthesis from mixed carbon substrates

I aim to integrate pathways that co-utilize diverse substrates such as C1 compounds (formate, methanol), C2 compounds (short-chain fatty acids), and dicarboxylic acids to enhance product diversity and efficiency. Leveraging metabolic bow-tie structures, particularly acetyl-CoA pathways, allows selective pressure-based optimization for high-yield product synthesis in oleaginous yeasts and PHA-accumulating bacteria like C. necator.

Aim 3: Decoupling growth and production to enhance bioconversion metrics and scalability

Decoupling biosynthesis from cellular growth promises consistent productivity across scales. Dynamic metabolic control and orthogonal pathway integration will optimize energy transduction and pathway flux for sustained high performance in bioprocesses. Using metabolic compartmentalization and selective gene deletions, I aim to redirect carbon flux exclusively towards product synthesis, enhancing stability and efficiency in biomanufacturing.

Teaching Interests

Engineering is about the real-world application of science. Students in engineering majors expect to learn science that will not only help them score high on tests but also enable them to apply their knowledge and skills to make a tangible impact. Overemphasizing the fundamental math and physics of engineering disciplines can cause lecturers to lose sight of connecting these concepts to real-world applications, often leading to a loss of student motivation. One core objective of my teaching philosophy is to balance the lecture content between fundamentals and anecdotes on how these concepts can be applied in reactors, heaters, and purifiers in plants.

My second core objective is motivation. I strongly believe that motivation is the key to education, and finding ways to motivate students—whether they are undergraduates in a lecture hall or graduate students and postdocs in the lab—is a core challenge in teaching. The motivation instilled by my high school chemistry teacher has brought me to where I am today, and my lifelong goal is to play a similar role in someone’s life. Everyone has different core values, and identifying these is crucial for motivating individuals. As a research supervisor and mentor, I will strive to understand each individual’s core values and instill motivation accordingly. I am eager to learn about every member under my guidance and approach them from different angles tailored to their needs.

The third core objective of my teaching philosophy is embracing diversity. During graduate school, I observed many colleagues struggling with different mentoring styles, whether hands-on or hands-off. Instead of adhering to a one-dimensional mentoring style and forcing students to adapt, I aim to be flexible and adjust my mentoring style to match the needs of each mentee. Not every PhD student needs to be an independent and autonomous researcher; some excel under detailed, step-by-step guidance. Understanding their styles will help guide their next career steps.

I am most knowledgeable and interested in teaching Kinetics, Biochemical Engineering, Biomolecular Engineering, Chemical Engineering Laboratory, and Bioseparation Processes, but I am open to teaching other subjects as well. I am also interested in organizing elective classes in Metabolic Engineering and Biomanufacturing, and Alternative Resources and Technologies for a Circular Carbon Economy. For Metabolic Engineering, I have ample teaching resources from a graduate-level elective class taught by my PhD advisor, and I can add insights from my own research in the field. For Circular Carbon Economy, my experiences in climate tech events and societies, including organizing the MIT Energy Conference, will provide valuable insights for the curriculum.