Microbial integration of plastics in the circular economy

Lead Research Organisation: University of Surrey
Department Name: Microbial & Cellular Sciences

Abstract

In this proposal we will develop the technology required to use two recalcitrant plastic polymers, polyethylene terephthalate (PET) and polyurethane (PU) as feedstock for microbial transformations required for a circular economy. In particular, we will focus on the transformation of PET and PU waste into the industrially relevant and more sustainable moieties for Bio-PU polymers. With this approach we will also enable the recycling of the Bio-PU product, completing this way a fully circular strategy for the sustainable production of an important material.
The success of PET as a packaging material is only comparable to its resilience to degradation in the environment. Likewise, production rates of PU are also increasing, with the caveat that the recycling procedures for PU are virtually non-existing. PET can be degraded to constituent monomers using physicochemical processes such as pyrolysis and, more recently, by enzymatic hydrolysis. PU, on the other hand, is not so well characterised in terms of enzymatic hydrolysis, but microbial activities against the polymer have been recently described.
The synthesis of the monomers required for Bio-PU has been achieved using standard carbon sources (e.g. glucose) in different organisms. In MIPLACE we will synthesise them in biotransformations using the products of hydrolysis of PET as the sole energy and carbon source. Preliminary results from members in the consortium show that this can be achieved although with low yields.
Despite their limited scope, these previous observations support that PET and PU are feasible substrates for bacterial growth. In this proposal we will expand on those works and establish PET and PU as general substrates for biotechnological applications including the development of bacterial communities that can directly feed on PET and PU as the sole carbon source without the need of a prior lytic step.
In MIPLACE we have devised a multidisciplinary strategy based on the use of microbial communities for the effective transformation of PET and PU into Bio-PU. Our workflow is based on the traditional design-build-test cycle of engineering disciplines. We will use a combination of environmental screening of microorganisms, rational design of strains and lab directed evolution to achieve this goal. We build on the complementary strengths of the partners involved, which include enzymology, synthetic biology, metabolic engineering, mathematical modelling, chemical engineering and biodegradation. At the same time, we will address the societal concerns associated to this research that are related to the public perception of the approach taken and the possibility of influencing changes in consumer behaviour.
Overall, MIPLACE will deliver the technological development required for incorporating plastic polymers in the circular economy, paving the way for new biotechnological approaches based on a material that would otherwise be condemned to end up as waste otherwise. By developing efficient microbial PET transformation processes, we aim to use these waste streams in a completely new approach as fossil-based carbon sources for the production of value-added materials, providing the economic incentive to increase end-of-life plastic collection in favour of a sustainable bio-based economy.

Technical Summary

The main goal of MIPLACE is to develop an efficient bio-based process that uses plastic waste as a feedstock to produce molecules of industrial interest. A fully circular approach will be applied to turn two types of plastic polymers, polyethylene terephthalate (PET) and polyurethane (PU), into the more environmentally friendly Bio-PU used as a construction and insulation material. For this, we will harness the potential of microbial communities to achieve the main goals of the proposal, namely: i) develop strategies for the effective hydrolysis of PET and PU monomers by taking advantage of natural or modified bacterial species expressing polyester hydrolases; ii) use engineered microbial communities to transform the hydrolysis products into products of interest; iii) use monomers resulting from PET and PU hydrolysis potentially in addition to other building blocks obtained from renewable sources (such as glycerol and acetate) to synthesise Bio-PU. As a result of this proposal we will contribute to the incorporation in the circular economy of two materials with limited recycling rates that are eventually discarded as waste. We will thereby create a novel path for their use as carbon source for microbial transformations that will expand beyond the focused applications described in this proposal.
We chose PET and PU as substrates because they are the only two types of plastic polymers derived from oil that can be readily degraded enzymatically to some extent. Both are polyesters, and a number of polyester hydrolase enzymes have been isolated capable of using PET and PU as substrates. In fact, members of this consortium have achieved the complete enzymatic hydrolysis of urban PET waste materials in vitro and used the resulting lysates to feed strains of the soil bacterium Pseudomas putida for the production of hydroxyalkanoyloxy-alkanoic acids (HAAs) and bioplastic polyhydroxyalkanoate (PHA) demonstrating the feasibility of the approach.

Planned Impact

Plastics are extremely successful materials with many properties that make them almost essential in our lives. They are versatile, lightweight, waterproof, easy and affordable to synthesise and difficult to degrade. As a consequence, it is estimated that to date 8.3 billion metric tons (MT) of virgin plastics have been produced directly from oil, out of which 6.3 billion MT ended up as waste. Out of all the plastic waste only 9% was recycled, whereas 12% was incinerated. The remaining 79% of plastic waste is stored in landfills or has been directly released into the environment. This has led to alarming levels of pollution due to environmental accumulation of plastics, especially in marine environments, with devastating effects on the fauna and flora and numerous toxicological effects derived from the intake of microplastics resulting from the degradation of larger polymers.
In MIPLACE we consider plastics, mainly of urban origin, as alternative microbial feedstocks. We propose the biological up-cycling of these recalcitrant polymers, for which we do not only require enzymatic hydrolysis but also the metabolisation of its products to produce the biomass required for the transformations. In addition, MIPLACE will create a similar stream for PU, for which there are currently no suitable collection or recycling technologies. As a result we will deliver a complete pipeline for the transformation of waste into Bio-PU.
As opposed to consolidated bioprocesses using only one strain that are commonplace in industry, in MIPLACE we will rely on microbial communities and their interactions to deliver our research agenda. This is motivated by the complexity of the plastic substrates used as a feedstock as well as by the relatively large numbers of target molecules that can be produced. Furthermore, a community approach will be advantageous for a number of reasons such as: i) the enzymes required for polymer hydrolysis are secreted and are accessible to the whole population, therefore enabling complex dynamics in which the desired outcome may not always be favoured and, for this reason we will devise ways to stabilise microbial cooperation in our setup; ii) the production of target molecules from mixed substrates is likely to benefit from the distribution of tasks within a community that can split the cost of production and boost the reactions involved through metabolic exchanges; iii) the division of tasks will also help to devise strategies for lab directed evolution of individual modules of the pipeline such as enzymes for improved hydrolysis without affecting other components of the pipeline.
We have identified a market pull (the development of sustainable PU-based materials) with a large potential for producing revenue as is evidenced from the PU market size (expected to be $26.24 billion by 2024 in Europe; projection by Grand View Research). Although it is unclear how much of that market would correspond to Bio-PU, its production is likely to increase in the coming years aligning with social awareness and implementation of policies to prevent plastic misuse. SOPREMA is one of the European companies leading this change and MIPLACE will contribute towards this goal by satisfying an increasing demand.
MIPLACE will also act as a technology push. Considering the problems associated to a saturated recycling industry, the enablemenet of alternative paths to standard recycling is of utmost importance for a number of reasons. They allow to recycle PET polymers that are normally discarded such as opaque PET. In addition, they could also contribute to increasing the recycling rates of PU specially of resilient crosslinked PU polymers. In MIPLACE we have opted for a process that is fully compatible with microbial transformations that can go beyond our main goal Bio-PU. We envisage MIPLACE yielding a 'jack of all trades' process for the production of other added-value molecules out plastic waste.

Related Projects

Project Reference Relationship Related To Start End Award Value
BB/T011289/1 12/03/2020 31/08/2020 £442,150
BB/T011289/2 Transfer BB/T011289/1 01/09/2020 11/03/2023 £380,700
 
Description We have isolated several microorganisms from the environment able to grow using the constituent monomers of PET, terephathalate and ethylene glycol as sole carbon source. These organisms are amenable for genetic manipulations and we have successfully used them for the recombinant expression of esterases that are active against PET. Moreover, we have developed a method to monitor the hydrolysis of PET conducted by these enzymes.
Exploitation Route We will make results and methods public via open access publications and materials (e.g. strains and enzymes) available upon request and as soon as possible after intellectual property protection (if required). DNA sequences will be made available through public repositories.
Sectors Agriculture, Food and Drink,Chemicals,Construction,Manufacturing, including Industrial Biotechology,Other

URL http://www.miplacebio.com
 
Title Simultaneous determination of terephthalate, protocatechuate and ethylene glycol by HPLC 
Description HPLC assays to determine hydrolytic activity of enzymes against plastic PET. The method is based on the differential affinity of the reaction products for a hydrophilic column. The concentration of all products is determined after separation using RID and DOD detectors, for respectively ethylene glycol and aromatics. 
Type Of Material Technology assay or reagent 
Year Produced 2021 
Provided To Others? No  
Impact This method can greatly expedite our enzymatic assays that so far were restricted to the use of PET analogs such as polycaprolactone for which not all enzymes used display activity. 
 
Title Repromin 
Description Model that integrates transcriptomic and proteomic data to quantify the theoretical size of the proteome produced by a microorganism. It allows to optimise strains that release proteome size that could be allocated for the recombinant production of proteins of interest. 
Type Of Material Computer model/algorithm 
Year Produced 2020 
Provided To Others? Yes  
Impact The method is described in Lastiri et al., 2020 Natural Chemical Biology (see my portfolio). It has been adopted by other researchers in order to improve bioprocesses such as industrial fermentations. 
URL https://www.nature.com/articles/s41589-020-0593-y
 
Description Accurate metrology of RNA levels 
Organisation LGC Ltd
Country Global 
Sector Private 
PI Contribution We design experiments and produce samples later analysed by LGC.
Collaborator Contribution Jim Huggett's team at LGC has brough expertise and in kind goods (reagents, instruments, etc) to accurate measure changes in RNA levels during couplings in gene expression. Understanding the mechanistic determinants of these couplings at the molecular level is critical for the efficient design of genetic circuits. LGC is currently measuring changes in RNA levels with the highest possible accuracy using qPCR and dPCR.
Impact No outputs yet. Multidisciplinary between molecular metrology and synthetic biology.
Start Year 2016
 
Description Bacterial hedging (UNAM-Mexico) 
Organisation National Autonomous University of Mexico
Department Center For Genomics Sciences
Country Mexico 
Sector Academic/University 
PI Contribution Support designing CRISPR interference methods and development of molecular tools and reporter strains.
Collaborator Contribution Computational modelling and analysis of gene expression networks
Impact Grant awarded from the Newton fund (Advanced fellowship) to foster collaborations with Mexico (see further funding for details). Interdisciplinary between systems and synthetic biology. Publications: Lastiri-Pancardo G., Mercado-Hernandez J.S., Kim J., Jimenez J.I. and Utrilla J. A quantitative method for proteome reallocation using minimal regulatory interventions (2019). Under second review in Nature Chem. Biol. Preprint available at https://www.biorxiv.org/content/10.1101/733592v1 Kim J., Darlington A.P., Salvador M., Utrilla J. and Jimenez J.I. Trade-offs between gene expression, growth and phenotypic diversity in microbial populations (2020) Curr. Opin. Biotechnol. 62:29-37
Start Year 2017
 
Description Bioplastics 
Organisation University College Dublin
Department School of Biomolecular and Biomedical Science UCD
Country Ireland 
Sector Academic/University 
PI Contribution In this collaboration we are contributing with materials, mainly engineered strains, that are optimised for biotechnological purposes and tested at UCD for relevant applications.
Collaborator Contribution Our collaborators at UCD Dr Narancic and Prof. O'Connor are experts in bioplastics. They use different culture conditions and analytical methods to determine the polyhydrohyalkanoate and polyhydroxybutyrate production yields of the strains generated in my laboratory.
Impact This collaboration has resulted already in a publication in the journal Microbial Biotechnology (https://sfamjournals.onlinelibrary.wiley.com/doi/full/10.1111/1751-7915.13712).
Start Year 2019
 
Description University of Zurich - microbial communities 
Organisation University of Zurich
Country Switzerland 
Sector Academic/University 
PI Contribution We have developed microbial strains that can be used to steer the dynamics of microbial communities. They do so because they have a modified iron metabolism. These strains can be used for population invasion.
Collaborator Contribution The laboratory of Prof. Kummerli at the University of Zurich specialises in the investigation of microbial communities in a variety of experimental models. In particular for this collaboration he supported a 3-month long internship of one of my team members who received training in single cell in vivo microscopy and the use of larvae of insects as animal models of microbial population dynamics.
Impact The collaboration resulted in a joint publication in the ISME journal (see link above).
Start Year 2019
 
Description ERA CoBiotech Status seminar 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact This was an online series of seminars organised by the ERA-CoBiotech programme of the EU to highlight projects funded through the scheme. The audience was composes of mainly academic and industrial researchers, as well as representatives from the EU administration and it was open to the general public. The seminars were well attended with >200 people connected for the talks. There was discussion after the presentation about the economic implications of the technology discussed.
Year(s) Of Engagement Activity 2020
URL https://subsites.wur.nl/en/show/ERA-CoBioTech-Status-Webinar-Series-2020.htm
 
Description Industry day 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact Presentation for industrial partners collaborating in taught postgraduate programmes at Imperial College. The day involved discussions with industrial researchers to explore future collaborations.
Year(s) Of Engagement Activity 2020
 
Description MIPLACE - Nature Biotechnology 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact The project was highlighted by Nature Biotechnology as a promising technology to tackle plastic waste resulting from a short interview.
Year(s) Of Engagement Activity 2020
URL https://www.nature.com/articles/s41587-020-0541-0
 
Description Miplace twitter feed 
Form Of Engagement Activity Engagement focused website, blog or social media channel
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact The twitter feed of the project MIPLACE (Microbial Integration of Plastics in the Circular Economy) was created in June 2020 as a way of interacting with a broad audience on a day to day basis. As of today (25/02/21) it has 250 followers and the posts have generated thousands of reactions.
Year(s) Of Engagement Activity 2020
URL https://twitter.com/miplacebio
 
Description Miplace web 
Form Of Engagement Activity Engagement focused website, blog or social media channel
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact The webpage for the project MIPLACE (Microbial Integration of Plastics in the Circular Economy) was released in June 2020 and since then it has had thousands of visits. As a result there have been a number of engagements including with journalists and publishers.
Year(s) Of Engagement Activity 2020
URL http://www.miplacebio.com
 
Description Press release - Trojan horse (Zurich) 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Media (as a channel to the public)
Results and Impact Press release by the media office of our collaborators at the University of Zurich resulting from a joint publication.
Year(s) Of Engagement Activity 2020
URL https://www.dqbm.uzh.ch/en/news/population-invasion-through-exploitation.html
 
Description Press release - Trojan horses (Imperial) 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Media (as a channel to the public)
Results and Impact Press release to highlight the publication of an article resulting from activities in the project. The news were picked by several webpages and social media.
Year(s) Of Engagement Activity 2020
URL https://www.imperial.ac.uk/news/210995/trojan-horse-bacteria-could-help-defeat/
 
Description Seminar to Life Sciences Imperial 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Professional Practitioners
Results and Impact Seminar given to the Dpt. of Life Sciences at Imperial College. This was an introduction to my research interests as a result of joining the Dpt. The talk was followed by interesting discussions and opportunities for collaboration.
Year(s) Of Engagement Activity 2020