Advanced analytical, chemometric, and genomic tools to identify polymer degradation products and potential microbial consumers in wastewater environments

The worldwide growth in the production of plastics and lack of appropriate waste management has led to unsustainable environmental pollution of global concern. Hence, determining the key drivers characterizing the degradation of polymers in water is a rising topic. Here we propose a workflow based on advanced high throughput data analysis and processing tools aiming at the characterization of (a) the degradation products of polymers exposed to an aquatic environment, and (b) the taxonomical composition of the potential microbial consumers' consortia. To test this approach, polycaprolactonediol (PCLD) polymer probes were exposed to different wastewater environments (influent, aerobic, and anaerobic denitrifying reactors) in four different wastewater treatment plants (WWTPs). Probes were extracted and analyzed by non-target liquid chromatography-high resolution mass spectrometry (LC-HRMS) and the acquired data were processed using advanced chemometric tools (Regions of Interest-Multivariate Curve Resolution-Alternate Least Squares, ROIMCR-ALS). Up to 26 components explaining ca. 69% of the variance were resolved, and 20 of these were further identified. Degradation was dominated by two processes: (a) hydrolysis of the ester groups present in PCLD and (b) formation of cyclic polycaprolactone oligomers. These transformation pathways occurred regardless of what were the WWTPs and the treatment stages, varying only the respective concentrations of the formed by-products. The composition of the microbial communities attached to the polymer and free-living in the surrounding water was characterized by 16S rDNA amplicon sequencing analysis. The two communities showed taxonomic differences and were unique in each WWTP treatment stage. Polymer-attached communities were tentatively proposed as potential consumers.

Automated summary

The worldwide growth in plastic production and insufficient waste management have resulted in significant environmental pollution. This study proposes a workflow utilizing advanced data analysis and processing tools to characterize the degradation of polymers in water, as well as the composition of microbial communities involved in their degradation. The results show that hydrolysis of ester groups and formation of cyclic polycaprolactone oligomers are the dominant degradation processes, and the composition of microbial communities varies among different wastewater treatment plants and stages. The microbial communities attached to the polymer may serve as potential consumers.