Our Inspiration

In 2016 a bacterium, Ideonella sakaiensis, was found that is able to use polyethylene terephthalate (PET) as a primary carbon and energy source (Yoshida et al., 2016). This bacterium secrets two different hydrolases into the exterior to execute the first two PET degradation steps (Yoshida et al., 2016). The first hydrolase, PETase, mainly breaks down PET to mono(2-hydroxyethyl) terephtalic acid (MHET). The second hydrolase, the MHETase, then digests MHET to terephthalic acid (TPA) and ethylene glycole (EG). The bacterium itself grows optimally within a pH range of 7-7,5 and a temperature of 30-37°C (Tanasupawat, Takehana, Yoshida, Hiraga, & Oda, 2016). It was also demonstrated that it cannot grow anaerobically and has a GC-rich genome (70,4%) (Tanasupawat et al., 2016; Yoshida et al., 2016). Later in 2018, the PETase was characterized and engineered to improve its performance (Austin et al., 2018).

TODO Text

The iGEM projects that inspired us

Degrading microplastic is not a new idea when it comes to iGEM projects. Similarly inspired by the works of Yoshida and his colleagues (Yoshida et al., 2016) a multitude of different teams have worked on comparable topics. We know that we are not after something completely new. But we wanted to do this right. So we chose a different organism and tried to tackle obstacles other teams failed to solve. Our work was inspired by TJUSLS project on PETase 2016 (1), we are intrigued by the effort Harvard BioDesign 2016 put into their project “Plastikback” (2) and the project of ASIJ Tokyo in 2016 struck the same nerve (3). The approaches by the Teams of Tianjin 2016 (4) and ITB 2017 (5) have gravely encouraged our project as well.

Chlamydomonas as a model organism

We propose that by combining a photosynthesis active organism with at least the optimized PETase and the MHETase we can create a new way of recycling PET or even degrade PET completely to CO₂ and H₂O. The organism is then able to use the CO₂ coming from the plastic as carbon source. We immediately thought of Chlamydomonas reinhardtii as an organism as it grows fast under energy-efficient conditions.