(219b) Bioconversion of plastic wastes into value-added products using thermal oxo-degradation

Over 8 billion tons of plastics have been produced, and the available strategies for its disposal have proven insufficient due to economic and environmental sustainability limitations. As a result, most of all plastic ever made has ended or will end in landfills and our ecosystems. Plastics are not biodegradable because the breakdown of the polymers into molecules that microorganisms can utilize is estimated to take thousands of years. However, combining thermal oxo-degradation (TOD) with biocatalytic conversion can drastically reduce the rate-limiting step of plastic degradation and open an avenue for plastic waste upgrading. TOD rapidly deconstructs polymer backbones while adding oxygen functionalities to the fragmented products. The products of this process with plastic feedstocks are mixtures of fatty substrates - including fatty acids and fatty alcohols – and hydrocarbons. In this study, a screening process was carried out to select a suitable microorganism for the bioconversion of thermally oxo-degraded high-density polyethylene (HDPE), the world's most common plastic. The TOD products were hydrophobic and not emulsified before testing carbon utilization, resulting in a solid floating at the surface of the culture. Remarkably, the selected organism overcame mass transfer limitations in the liquid culture and grew with TOD products as its sole carbon source. The growth profile was even comparable to glucose controls. This microorganism could be leveraged as a microbial cell factory, or its biomass could be turned into single cell protein, resulting in waste upcycling. These findings serve as proof-of-concept and showcase the potential of our novel approach.