Collaborative Research: Enzyme-Mimicking Catalysts for Cellulose Processing

With the support of the Chemical Catalysis Program in the Division of Chemistry, Yan Zhao of Iowa State University and Sijia Dong of Northeastern University are studying the development of synthetic catalysts by molecular imprinting to mimic natural cellulases. Fossil fuels continue to be the dominant source of energy and chemical feedstocks to humanity but concerns about their sustainability and negative environmental/ecological impact have prompted many to look for alternatives. Lignocellulosic biomass from plants is a viable alternative. It is a renewable, carbon-neutral material produced at a scale of 170–200 billion tons per year. Unfortunately, the depolymerization of cellulose that is a key step in biomass conversion is hampered by the chemical stability of cellulose polymers and the highly crystalline nature of cellulose fibers. Although natural cellulases are powerful catalysts for cellulose depolymerization, they are often expensive to produce and difficult to recycle. In contrast, the synthetic catalysts that the Zhao and Dong research groups are developing are robust polymeric nanoparticles that can tolerate high temperatures, organic solvents, and other adverse reaction conditions. They are expected to greatly expand the operation window of the depolymerization process, making it more industrially viable. The multidisciplinary nature of this research will provide valuable training to students by exposing them to catalysis, polymer chemistry, computational chemistry, enzymology, and physical organic chemistry. The education and outreach activities of the Zhao and Dong teams involve both on- and off-campus programs that aim to engage undergraduates in research and increase the exposure of K–12 students to STEM (science, technology, engineering and mathematics). The depolymerization of cellulose is a key step in biomass conversion that is hampered by the stability of the glycosidic bonds and high crystallinity of cellulose fibers. The proposed research is a combined experimental and theoretical investigation on nanoparticle catalysts to mimic endocellulase, exocellulase, and β-glucosidase, respectively, through the development of molecularly imprinted nanoparticles. The experimental work at Iowa State University focuses on the optimization of the binding and catalytic domains of the synthetic catalysts inspired by the natural enzymes. The theoretical work at Northeastern University centers on computational simulation of the active sites for a better understanding of catalysis and is being used to guide and design active sites. If successful, the research will yield synthetic catalysts for cellulose hydrolysis than can compete with natural cellulases in activity but that are much easier to prepare and recycle. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.