(225i) Bioconversion of Plastic Wastes into Value-Added Products Using Thermal Oxo-Degradation

Over 8 billion tons of plastics have been produced, and over half of it has ended or will end in landfills or the environment. Plastic accumulates in the environment because evolution has not had enough time to develop a mechanism to break down plastics into molecules that can be recycled by nature. Instead, it can take a thousand years for plastics to break down via abiotic action, making it the rate-limiting step in plastic biodegradation. Thermal oxo-degradation (TOD) can accelerate this rate-limiting step by rapidly deconstructing the polymer backbone and inserting oxygen functionalities to produce lipids and hydrocarbons. At this point, engineered microbes can be employed to convert the carbon that originated from plastic wastes into higher-value products to promote a circular economy and prevent plastic pollution. In this work, non-conventional yeasts were selected against model compounds representative of the composition of thermally oxo-degraded High-Density Polyethylene (HDPE), the most common type of plastic. The best-performing microorganism was able to use TOD products from plastics as the sole carbon source without emulsification, overcoming the mass transfer limitations presented by a hydrophobic and solid substrate. The already remarkable growth profile of the microorganism was improved via adaptative laboratory evolution, increasing the growth rate by >200%. This work represents the proof-of-concept for a promising plastic waste upcycling approach and presents a non-conventional yeast with the potential to become a microbial cell factory capable of using heterogeneous and hydrophobic carbon sources as raw material.