UC San Diego

Thermoplastic polyurethanes (TPUs) are a widely-used synthetic polymer that are involved in the production of many items. Due to its widespread applications, the ensuing industrial production of TPUs has led to a worldwide increase of TPU waste. However, there is currently no available commercialized recycling process for TPU, resulting in TPU waste either being incinerated or accumulating in landfills. These main methods of dealing with TPUs pose environmental and health issues, necessitating a novel approach to safely remove TPU waste. A promising solution is the biodegradation of TPU via microorganisms, however the mechanisms of TPU biodegradation and TPU-degrading microorganisms are not well-known. The focus of this thesis is the screening and characterization of TPU-degrading microorganisms, in particular the Bacillus species, as they are known to have TPU-degrading capabilities. Growth in compost, capability of TPU degradation, and genetic tractability were assessed from over 140 Bacillus species. In this thesis, it was determined that i). most screening approaches in evaluating characteristics of potential host strain candidates were unable to produce consistent data to verify the strain growth phenotypes in terms of growth rates and final cellular densities, and ii). experiments screening growth on TPUs indicate that strains have preferences in degrading certain TPUs, requiring approaches like adaptive laboratory evolution (ALE) to optimize degradation. In addition, characterization of screened candidates will be utilized as starting platform strains for further TPU degradation research and optimization of the degradation pathway. Ultimately, these evolved strains will be utilized as an environmentally-friendly way of removing TPU waste.