The accumulation of polyethylene terephthalate (PET) plastics in the environment has had lasting negative effects on the natural environment. Recently, Yoshida et al. discovered a novel bacterium, I. sakaiensis, which is able to degrade PET plastic and utilise it as a major carbon and energy source1. Two key enzymes were identified in the bacterium’s PET degradation pathway: PET hydrolase (PETase) and MHET hydrolase (MHETase). PETase hydrolyses the PET polymer to mono-(2-hydroxyethyl) terephthalate (MHET), MHETase then hydrolyses MHET to the plastic precursors, terephthalic acid and ethylene glycol. When isolated these chemicals can be used in the production of ‘virgin’ plastic, a method that provides an attractive route for the biological recycling of PET plastics. Here, we present the preliminary findings from our biophysical characterisation of MHETase. We hope to improve the stability and activity of this enzyme to levels acceptable for industrial applications. To this end, we have employed techniques such as computational protein design and directed evolution, in combination with a unique MHETase activity assay.