David Rivera-Kohr, an IPiB graduate student, will be defending his Ph.D. research on November 25, 2025. His research in the Fox Lab explored biochemical mechanisms used to degrade waste products and convert municipal waste into biofuel.
Rivera-Kohr focused on Paenarthrobacter, a bacterium he helped isolate from the Dane County Landfill with collaborators from Erica Majumder’s lab in the Department of Bacteriology. This bacterium consumes caprolactam, a small molecule byproduct of nylon manufacture that can degrade air and water quality. Rivera-Kohr used techniques including mass spectrometry and enzyme assays to determine the metabolic pathways and enzymes that Paenarthrobacter uses to digest caprolactam. His research identified an enzyme that hydrolyzes caprolactam and new substrates that interact with the enzyme.
“The pathway that we identified is very similar to a pathway that was found in a distantly related bacterium also known to digest caprolactam,” says Rivera-Kohr. “Hopefully this work on the enzymes used to digest caprolactam reveals insights into metabolic mechanisms that bring us a step closer to using [Paenarthrobacter] as a bioindustrial tool.”
His research has been published in Microbiology Resource Announcements.
Interested in furthering his understanding of how biochemical processes can be harnessed to process and recycle waste products, Rivera-Kohr also worked on a multi-disciplinary project in collaboration with engineers and researchers at the Department of Chemical and Biological Engineering, Wisconsin Energy Institute, Idaho National Laboratory, and Michigan Technological University. The researchers explored organic solvents that can be used to extract plastics from municipal waste for recycling. Rivera-Kohr focused on using enzymes to break down carbohydrates in the extracted municipal waste, which can then be repurposed as biofuel.
Rivera-Kohr joined IPiB with an interest in studying plastic biodegradation. He was drawn to the program thanks to the Fox Lab’s focus on using synthetic biology techniques to break down molecules for use in biofuels, as well as UW-Madison’s broad-reaching development of sustainability-focused research. “Climate change and environmental decay are defining issues of our time,” he says. “I’m excited to be one of the people working to address this problem for our planet.”
To learn more about Rivera-Kohr’s research, attend his Ph.D. defense, “Turning trash to treasure: biological solutions for caprolactam degradation and municipal solid waste valorization” on Tuesday, November 25 at 1:00 p.m. CT in Room 1211 of Hector F. DeLuca Biochemical Sciences Building.
Written by Renata Solan.