The Importance: Plastic waste is one of the most pressing environmental issues of our time, with predictions that world plastic accumulation will exceed 34 billion tons by 2050 (Samak et. al 2020). This is especially concerning considering the negative effects microplastics can have on the natural environment and human health. Polyethylene terephthalate (PET) is used in the production of plastic water and soda bottles, making it one of the most widely used plastics in the world. While PET is one of the most widely recycled plastics, recycling is energy and resource intensive and often not economical. In recent years, the discovery of hydrolytic enzymes from microorganisms that break down PET has created a more environmentally-friendly route to recycling PET waste. Unfortunately, enzymatic recycling of plastic has not yet been commercialized due to poor reaction kinetics and low conversions of PET under industrially relevant conditions. This study investigates approaches to improve reaction conditions for PET degradation using enzymes.
Our Project: The well researched method of PETase is a catalyst for a hydrolysis reaction in water. The focus of our project is to investigate methods to perform transesterification on the PET plastic. Transesterification breaks down the PET into products that can be directly repolymerized into PET.
Results:
Surfactant Addition
When the pH is less than the pI of the enzyme, negatively-charged surfactants can bind to positively-charged amino acids
Crude Humicola Insolens Cutinase was used at first to determine reaction viability, then methods were tested with purified Fast PETase
varying concentrations of the anionic surfactant AOT were added to 1.1 mg/ml of Humicola Insolens Cutinase and Fast PETase in Bis-Tris propane buffer (pH 7.5) containing 50 mM CaCl2
The research has found some starting success on ion pairing HiC and PETase into isooctane, but with unconfirmed results on the activity levels within the organic solvent at this time. The research results have not yet been published so details will not be provided online.