Converting Plastic Waste into Macro-Nutrients

Amy Rees, Chloe Forenzo, Dr. Mark Blenner
Department of Chemical and Biomolecular Engineering, College of Engineering, Computing and Applied Sciences Clemson University

Abstract

Most plastics are discarded in landfills and are not easily recyclable. One solution to mitigate the large quantities of plastic waste is to utilize thermochemical processes to break it down into various hydrocarbon molecules that can be used as a substrate to grow engineered yeasts. Yeast can grow on media made up of these assorted hydrocarbons and metabolize it into yeast biomass which could function as a food source. The oleaginous yeast Yarrowia lipolytica has the ability to efficiently metabolize various hydrophobic substrates. Specifically, we have researched the various pathways of lipid metabolism for Y. lipolytica; focusing on branched and straight alcohols, various chain-length branched and straight alkanes, carboxylic and dicarboxylic acids, esters, and saturated and unsaturated fatty acids. By identifying these pathways, the natural metabolic capabilities of Y. lipolytica can be better understood and enhanced, and the figures can be utilized to identify gaps in its metabolic capabilities. Understanding these gaps can then aid in designing experiments in which the yeast can be engineered in order to improve its ability to metabolize plastic waste components.

Introduction

Due to their high reproducibility and low cost, devices and materials made of synthetic polymers are increasingly being utilized in society, thus contributing to high rates of their disposal in the environment. The ideal synthetic polymers to be used are plastics with structures that are susceptible to biological degradation. In order to minimize accumulation of this waste, it is necessary to understand not only the enzymes which aptly degrade biodegradable plastics, but also the microorganisms that produce these enzymes. By identifying and investigating the microorganisms that can efficiently produce these enzymes, reliable high rates of biodegradable plastic degradation can be achieved.

Materials and Methods

Literature searches were conducted to gather information and identify gaps in the knowledge on hydrocarbon metabolism in Y. lipolytica. These searches aimed to  identify key pathways, enzymes, and genes involved in the breakdown of branched and long-chain alkanes, fatty acids, and alcohols. Existing figures depicting hydrocarbon metabolism in various organisms were synthesized to construct detailed figures for these pathways in Y. lipolytica. Using these figures, unknown enzymes and genes in the pathways were identified. UniProt and NCBI BLAST tools were then utilized to identify potential genes in Y. lipolytica necessary for hydrocarbon metabolism.