Plastic pollution, a global challenge: How do we find the best-plastic eating bacteria in nature?

"Petroleum-based plastics are designed to be extremely stable and durable. Currently, about 360-450 million tons of synthetic polymers are produced annually and much of this is only meant for single use. Recycling hardly exists: more than 90% of all synthetic and fossil-derived plastics are incinerated or end up either in landfills or directly in the environment. Most plastic waste is composed of single or mixed materials consisting of the polymers: polyurethane (PUR), polyethylene (PE), polyamide (PA), polyethylene terephthalate (PET), polystyrene (PS), polyvinylchloride (PVC), epoxy-based polymers (EP), polypropylene (PP) and tire rubber. Within this framework, microbial- and enzyme-driven plastics degradation has been studied for less than a decade and functional enzymes are known for only a fraction of the fossil-fuel-based polymers. Few enzymes and microorganisms are capable of degrading PA oligomers, ester-based PUR, PET and natural rubber, and no verified enzymes are known that degrade PE, PVC, PP, PS, EP and ether-based PUR. These represent the majority of all synthetic polymers.

"Thus, the identification of microbial enzymes and pathways acting on most of the current polymers is a major and urgent task. In this seminar, I will summarize our efforts to identify novel plastics-active enzymes. We established a full pipeline to identify plastic-active enzymes from Hidden-Markov-Model-based in silico screenings of global metagenome datasets to in vitro protein production and functional verification, characterization, and structural elucidation. We identified more than 10 novel PET-active enzymes originating from diverse bacterial lineages. Amongst, others, we have identified the first PETases in the phylum of the Bacteriodota and the first archaeal derived PETase from Candidatus Bathyarchaeota archaeon. Finally, I will report on our ongoing efforts to enrich the PETase diversity even further using combined metagenome and evolutionary tools and to identify nylon-active enzymes."