Report
Teaser, summary, work performed and final results
Periodic Reporting for period 1 - P4SB (P4SB – From Plastic waste to Plastic value using Pseudomonas putida Synthetic Biology)
Teaser
Two hundred seventy five million tons of plastic were produced in 2010 alone, with Europe accounting for ~55 million tons/year. The environmental impact of these primarily oil-based plastics, specifically PET and PU, has been broadly discussed. The use of PET for packaging...
Summary
Two hundred seventy five million tons of plastic were produced in 2010 alone, with Europe accounting for ~55 million tons/year. The environmental impact of these primarily oil-based plastics, specifically PET and PU, has been broadly discussed. The use of PET for packaging, especially in the beverage industry, has contributed significantly to reducing energy expenditure during transport. However, recycled PET is of lower quality and current recycling techniques are barely competitive, leading to an overall European PET recycling rate of less than 30%. PU, on the other hand, is used extensively in a wide range of applications including construction, transportation, furniture and medicine. Since many PU types have a thermoset nature with covalent bonds, one of the main concerns for this product is the notable lack of end-of-life recycling, with recycling rates below 5%. This ultimately leads to an increased plastic pollution of natural habitats. For instance, significant amounts of plastic waste contribute to the large-scale pollution of the oceans, also referred to as “the Great Pacific Garbage Patchâ€.
In order to counteract these problems, the revised EU Waste Framework Directive has set a minimum plastic recycling target of 50% for household waste and 70% for building and construction waste, which must be reached by all EU Member States by 2020. The European Union emphasizes this efficient use of waste in the Focus Area “Waste: a resource to recycle, reuse and recover raw materials.†However, without a clear technology roadmap – let alone an appealing market strategy, this increase in recycling rates will not be achievable. On this background, P4SB proposes the engineering of a new-to-nature biological route for the conversion of PET and PU waste to added value bio-products, which will empower the recycling industry to a qualitatively new dimension. For PET, we specifically target the lowest quality post-consumer products that are not amenable to traditional recycling methods. When successful, PET and PU waste can be established as novel second generation carbon sources for bio-products. Thus, through Synthetic Biology, P4SB will enable new value chains across sectors including materials, chemicals, and environmental technologies within the framework of a sustainable knowledge-based bio-economy that will ultimately be to the benefit of the economy, environment and society.
Work performed
We aim to achieve the sustainable and environmentally friendly bioconversion of oil-based plastic waste into fully biodegradable bioplastics. This concept of plastic up-cycling will be proven through four major parallel research lines (see figure).
1. Plastic depolymerisation
Although plastics are generally considered to be very recalcitrant in nature, there are microbes and enzymes that can degrade them. We have identified PET and PU degrading enzymes and characterized their activity. We have started to engineer the enzymes themselves towards a greater activity, stability and efficiency, and we have also optimized the process in which these enzymes are applied to degrade plastic waste.
2. Monomer metabolism
The enzymatic depolymerization of plastic leads to plastic monomers such as terephthalate and ethylene glycol. We have engineered our bacterial P4SB workhorse Pseudomonas putida, convincing it to eat some of these monomers and use them for growth.
3. PHA production
Poly-hydroxyalkanoates (PHA) are carbon storage polymers of Pseudomonas. In other words, they are the equivalent of our fatty tissue. PHA is a biodegradable bioplastic that is excellently suited for applications in e.g., adhesives and films. We have identified conditions in which Pseudomonas ‘gets fat’ from plastic monomers, and have also convinced the bacteria to produce new types of PHA and PHA-derived chemicals.
4. PHA secretion
An efficient PHA production process substantially relies on an efficient way to get the product out of the bacterial cells. We have developed several concepts to make this process more efficient, and have started to test these concepts on our bacteria.
These parallel activities must be brought together into a complete process. In order to do this efficiently, we are developing new synthetic biology tools to more effectively engineer our bacteria, and we are making and using computer-based models of our enzymes, bacteria, and processes, in order to understand and predict our results. We are also actively communicating with the scientific community, but also with a broader audience in magazines, on the radio and even on TV. The P4SB project is being coordinated by the RWTH Aachen University.
Final results
P4SB is progressing towards the realization of the novel value chain from low-grade plastic waste to high value bioplastic. We named three visible social impacts that will emerge in the long run if P4SB is successful. The main driver for increasing recycling rates of PET and PU is an economic incentive that we see in the production of bioplastic and therefrom derived products. With such an incentive in place, the collection rate will improve, but even more importantly the recycling rate will increase.
After 18 months, the P4SB consortium achieved progress beyond the state of the art in single technologies. Examples are the up-scaled depolymerization of PET at increased temperatures and the production of PHA from single PET monomers. While these technology developments have their own merit, the consolidation of technologies is ultimately expected to achieve truly novel options for the recycling industry. So far the main socio-economic impact is on the consortium partners who develop new knowledge, experience and technology.
The academic partners supervised more than 10 bachelor and master theses that were dealing with aspects of P4SB. Besides the technical training, the students involved achieved a solid understanding of the plastic recycling challenges the EU, and countries worldwide, face. Educating the next generation of biotechnologist, synthetic biologist, and bioprocess engineers will help to implement novel value chains as envisaged in P4SB, but also in the upcoming bioeconomy. The outlook for education is the contribution to a MOOC that is covering many aspects of bioplastics.
The outreach, especially via the web, but also via traditional media formats like TV, helps to inform the public about the challenges around plastic waste and the novel approach we are developing. Early feedback from a wide variety of stakeholders is generally positive. Further impact is created by presenting P4SB mostly in scientific settings. A scientific highlight was the biannual Symposium on Biopolymers in Madrid with seven seminars from P4SB partners, including an industry session, with a keynote lecture from Prof. Averous.
In summary, the continuous progress of P4SB is attracting attention (public, but also industry) that until now already generated significant impact. The operation of the workflow will be presented in a P4SB publication and will be a test case how an academic publication will generate attention and subsequently impact. Especially further planned progress on the plastic degrading enzymes and the whole-cell catalyst promises exciting new insights into the envisioned P4SB process.
Website & more info
More info: http://www.p4sb.eu.