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Team:TU Darmstadt/Project
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Overview
Since the discovery of Polyethylene terephthalate (PET) in the 1940s, it has become the most widely manufactured synthetic. In 2012, global annual production exceeded 100 million tons. Its popularity also creates the issue of PET waste. In Western countries today, less than 70% of PET produced are recovered by common means of recycling. Biological processes currently play no role, as its chemical properties make PET inert to biological degradation.
Recently it was discovered that the erosion of PET in a maritime environment ultimately creates nanoparticles with undesired characteristics, as these particles tend to accumulate toxic substances on their surface. This poses a growing threat to the environment and a serious health risk. Therefore, developing new methods for PET degradation became an urgent issue. We suggest the development of a bacterial recycling system, transforming PET waste into harmless, environmentally benign compounds which can be used in a wide range of applications. Thus converting PET waste into a new ressource preventing pollution by making it too useful to toss away.
How would such a bacterial recycling system look like and what features are required?
First of all our genetical modified organism (GMO) would need to be able to digest the PET decomposing it into its terephtalic acid (TPA) subunits. Due to its chemical properties TPA uptake by diffusion isn't possible at pH higher than 3.0, a condition in which Escherichia coli (E. coli) the most common microogranism in genetics, can't be cultivated. This fact makes it necessary to implement a specialised TPA uptake system in order to enable E. coli for an uptake at pH 7.0. There are multiple reasons for which we decided to use E. coli as our host bacteria. It is easy to cultivate, secure to handle and tons of different strains and materials are available. Most important is the circumstance that the genome of E. coli is well known and understood. This enables us to modify and insert proteins as we please. Furthermore even if E. coli is able to absorb TPA, it can't use it in its metabolism. Therefore we are required to insert additional enzymes to 'adjust' the metabolic pathway enabling E. coli of using the TPA as an engergy source. Briefly we need to insert enzymes for degradation, transport (uptake) and metabolism. This may sound easy, but it isn't. First of all E. coli is a living system. It mutates, modifies, dies and
