The sustainability of plastic materials implies attaining a renewable origin and recyclable nature. Unfortunately, both conditions are far from being fulfilled by the current industry. In the polyester sector, PET [poly(ethylene-terephthalate)], one of the most common plastics, has a petrochemical origin. Happily, PEF [poly(ethylene-furandicarboxylate)] is emerging as a biobased alternative to PET. Moreover, enzymatic biocatalysis can contribute to the industrial and environmental feasibility of bioplastics with next generation technologies for the synthesis and recycling of both building blocks and polymers. For PEF and other polymers, esterase-type enzymes can be tailored for ad hoc depolymerization reactions. Moreover, oxidase-type enzymes are called to provide selective and environmentally-friendly alternatives to convert HMF (5-hydroxymethylfurfural) from biomass sugars into the PEF building-block FDCA (2,5-furandicarboxylic acid).
Despite this potential, some of the most relevant enzymes —such as HMF oxidases and aromatic polyesterases— are not optimally suited to oxidize or hydrolyze plastic compounds (since they naturally evolved to act on their natural counterparts). Therefore, protein engineering is mandatory to optimize them in terms of substrate specificity and operational conditions. In this process, rational engineering will be possible when supported by extensive computational simulations of the access, accommodation and reaction of target substrates at the active site of the selected enzymes. For these studies, advanced software simulating substrate binding by the enzymes and their engineered variants needs to be used. This will be combined with datasets of relevant enzymes and predictive models by regression simulation and machine learning.
Some commercial enzymes, such as catalases and lipases, can be directly used by the polymer industry, taking advantage of the wide repertoire available. However, production of new enzymes or engineered variants of key enzymes (HMF oxidases and esterases) is still to be optimized, using heterologous expression hosts, adequate fermentation technologies and process intensification. Finally, the biotechnological processes for the production of both plastic polymers (from FDCA) and building blocks (from HMF) are also to be optimized in terms of reaction conditions and downstream processing. Then, improvements (related to higher specificity and milder reactions) in the industrial and environmental feasibility of production and/or recycling of furanic polymers (PEF included) are expected, by the use of enzymes and processes specifically tailored for the optimized biosynthesis and/or depolymerization of these bioplastics.
FURENPOL combines the relevant actors to fulfill the main studies mentioned above in an interdisciplinary consortium including Research and Industrial representatives for both the Biotechnology and Plastic (synthesis and recycling) sectors. The former includes the CSIC coordinator (groups of Biotechnology for Lignocellulosic Biomass and Microbial Systems and Protein Engineering at CIB) with large background in industrial enzymes, the Barcelona Supercomputing Center (group of Electronic and Atomic Protein Modeling) providing its supercomputational facilities, and the UAB (department of Chemical, Biological & Environmental Engineering, and Pilot-Plant) optimizing enzyme production and target reactions, together with the company Nostrum Biodiscovery (NBD) that will provide its experience in protein tailoring, required for successful application in the plastic sector and biotechnology valorization. Then, evaluation of the above applications for the enzymatic synthesis and recycling of plastic building blocks and polymers will be performed by the Technological Institute of Plastics AIMPLAS (Chemical Technology and other departments) acting as a link with the companies UNEMSA (interested in furanic plastic adhesives), ACTECO (a plastic-recycling company) and the above mentioned NBD.
Project PLEC2021-007690 funded by MCIN/AEI/10.13039/501100011033 and by the European Union NextGenerationEU/PRTR.