Off-campus Michigan Tech users: To download campus access theses or dissertations, please use the following button to log in with your Michigan Tech ID and password: log in to proxy server
Non-Michigan Tech users: Please talk to your librarian about requesting this thesis or dissertation through interlibrary loan.
ENRICHED MICROBIAL CONSORTIA FROM NATURAL ENVIRONMENTS PROVIDE NOVEL METHOD FOR UPCYCLING PLASTIC WASTE
Date of Award
Campus Access Dissertation
Doctor of Philosophy in Biological Sciences (PhD)
Administrative Home Department
Department of Biological Sciences
Committee Member 1
Committee Member 2
Committee Member 3
Presently, polyethylene terephthalate (PET) plastic waste pollutes the environment, and global food production is inadequate to support the growing population. A system that upcycles plastic into edible microbial protein powder may solve both problems. Many microorganisms can utilize plastic to produce microbial biomass containing fats, nutrients, and proteins. Microbial plastic biodegradation is very slow; however, coupling biodegradation with chemical pre-processing may substantially increase degradation rates. Previous work has used bioengineered microbial isolates to upcycle plastic. In contrast, this work will use microbial communities to process pre-processed plastics. First, we enrich microorganisms from natural environments to obtain communities which grow on terephthalate and terephthalamide (products of PET pre-processing). We demonstrate that terephthalamide (thought to be antimicrobial) is biodegradable, and that microorganisms able to grow using terephthalamide and terephthalate are widespread. This finding shows that there is great potential for microbial degradation of pre-processed PET. Second, we demonstrate that the enriched microbial communities can degrade chemically pre-processed PET without added growth medium. Growth tests on additional depolymerized polymers (polyethylene, spandex, nylon, mylar, and polyurethane) showcase the versatility of communities. Thirdly, we explore the mechanism of versatility by investigating the roles of generalist and specialist species in the microbial communities. Results showed that the coexistence of specialists and generalists may be essential to the microbial community’s ability to flexibly biodegrade mixed plastic waste streams. This work shows that using microbial communities, instead of isolates, to process plastic waste results in increased flexibility to process multiple plastic wastes.
Schaerer, Laura G., "ENRICHED MICROBIAL CONSORTIA FROM NATURAL ENVIRONMENTS PROVIDE NOVEL METHOD FOR UPCYCLING PLASTIC WASTE", Campus Access Dissertation, Michigan Technological University, 2023.