Comparative biodegradation analysis of three compostable polyesters by a marine microbial community

Abstract

ABSTRACT Biodegradable plastics are one of the possible solutions for reducing plastic waste, yet the mechanisms and organisms involved in their degradation in the aquatic environment remain understudied. In this study, we have enriched a microbial community from North Sea water and sediment, capable of growing on the polyester poly(butylene succinate). This culture was grown on two other biodegradable polyesters, polycaprolactone and a poly(butylene adipate-co-terephthalate) blend. The differences between microbial community structure and biodegradation activity on these three polymers were determined by metagenomics, metaproteomics, and respirometry analysis. In this study, we observed that the polymer type drives the community structure and determines its biodegradation capability. When the PBS-enriched culture grew on the poly(butylene adipate- co -terephthalate) blend, the community was more diverse, yet showed the lowest biodegradation percentage, while poly(butylene succinate) and polycaprolactone resulted in a less diverse community but much higher biodegradation activity. The dominating species were Alcanivorax sp., Thalassobius sp., or Pseudomonas sp., depending on the substrate. In general, we have observed that Gammaproteobacteria were more abundant and active within the biofilm on the polymers and Alphaproteobacteria within the free-living fraction of the enrichments. Three putative hydrolases were recombinantly expressed and their hydrolytic activity on all polymers tested was verified. In conclusion, we showed that all three plastics can be biodegraded by bacteria naturally occurring within the marine environment. IMPORTANCE Biodegradable plastics can be used in applications where the end product cannot be efficiently recycled due to high levels of contaminations, e.g., food or soil. Some of these plastics have a dedicated end of life, such as composting, but their degradation in the marine environment is poorly understood. In this study we showed that marine microbial communities can degrade a range of biodegradable polymers with different physical and chemical properties and use these as a sole carbon source for growth. We have also provided insights into the degradation mechanisms using a combined metagenomic and metaproteomic approach. In addition, we have identified three new enzymes that are capable of degrading both aliphatic polymers and aliphatic-aromatic copolymers, which can be used for biotechnological applications.