Plastic-degrading microbial communities reveal novel microorganisms, pathways, and biocatalysts for polymer degradation and bioplastic production.

Plastics derived from fossil fuels are used ubiquitously owing to their exceptional physicochemical characteristics. However, the extensive and short-term use of plastics has caused environmental challenges. The biotechnological plastic conversion can help address the challenges related to plastic pollution, offering sustainable alternatives that can operate using bioeconomic concepts and promote socioeconomic benefits. In this context, using soil from a plastic-contaminated landfill, two consortia were established (ConsPlastic-A and -B) displaying versatility in developing and consuming polyethylene or polyethylene terephthalate as the carbon source of nutrition. The ConsPlastic-A and -B metagenomic sequencing, taxonomic profiling, and the reconstruction of 79 draft bacterial genomes significantly expanded the knowledge of plastic-degrading microorganisms and enzymes, disclosing novel taxonomic groups associated with polymer degradation. The microbial consortium was utilized to obtain a novel Pseudomonas putida strain (BR4), presenting a striking metabolic arsenal for aromatic compound degradation and assimilation, confirmed by genomic analyses. The BR4 displays the inherent capacity to degrade polyethylene terephthalate (PET) and produce polyhydroxybutyrate (PHB) containing hydroxyvalerate (HV) units that contribute to enhanced copolymer properties, such as increased flexibility and resistance to breakage, compared with pure PHB. Therefore, BR4 is a promising strain for developing a bioconsolidated plastic depolymerization and upcycling process. Collectively, our study provides insights that may extend beyond the artificial ecosystems established during our experiments and supports future strategies for effectively decomposing and valorizing plastic waste. Furthermore, the functional genomic analysis described herein serves as a valuable guide for elucidating the genetic potential of microbial communities and microorganisms in plastic deconstruction and upcycling.

Characteristics of low-temperature plasma for activation of plastic-degrading microorganisms.

Plastic pollution is a problem that threatens the future of humanity, and various methods are being researched to solve it. Plastic biodegradation using microorganisms is one of these methods, and a recent study reported that plastic-degrading microorganisms activated by plasma increase the plastic decomposition rate. In contrast to microbial sterilization using low-temperature plasma, microbial activation requires a stable plasma discharge with a low electrode temperature suitable for biological samples and precise control over a narrow operating range. In this study, various plasma characteristics were evaluated using SDBD (Surface Dielectric Barrier Discharge) to establish the optimal conditions of plasma that can activate plastic-degrading microorganisms. The SDBD electrode was manufactured using low-temperature co-fired ceramic (LTCC) technology to ensure chemical resistance, minimize impurities, improve heat conduction, and consider freedom in designing the electrode metal part. Plasma stability, which is important for microbial activation, was investigated by changing the frequency and pulse width of the voltage applied to the electrode, and the degree of activation of plastic-degrading microorganisms was evaluated under each condition. The results of this study are expected to be used as basic data for research on the activation of useful microorganisms using low-temperature plasma.

Living in a bottle: Bacteria from sediment-associated Mediterranean waste and potential growth on polyethylene terephthalate.

Ocean pollution is a worldwide environmental challenge that could be partially tackled through microbial applications. To shed light on the diversity and applications of the bacterial communities that inhabit the sediments trapped in artificial containers, we analyzed residues (polyethylene terephthalate [PET] bottles and aluminum cans) collected from the Mediterranean Sea by scanning electron microscopy and next generation sequencing. Moreover, we set a collection of culturable bacteria from the plastisphere that were screened for their ability to use PET as a carbon source. Our results reveal that Proteobacteria are the predominant phylum in all the samples and that Rhodobacteraceae, Woeseia, Actinomarinales, or Vibrio are also abundant in these residues. Moreover, we identified marine isolates with enhanced growth in the presence of PET: Aquimarina intermedia, Citricoccus spp., and Micrococcus spp. Our results suggest that the marine environment is a source of biotechnologically promising bacterial isolates that may use PET or PET additives as carbon sources.

Microplastics spatiotemporal distribution and plastic-degrading bacteria identification in the sanitary and non-sanitary municipal solid waste landfills.

The municipal solid waste landfill (MSWL) is an important source of microplastics (MPs) and a huge bioreactor for plastic-degrading microorganisms (PDM). However, the spatiotemporal distribution and degradation mechanisms of MPs in MSWLs are unclear. Therefore, they were studied using the samples drilled in a sanitary landfill (SL) and an non-sanitary landfill (NSL). The results showed that there were a lot of polyethylene (PE), polypropylene (PP), polystyrene (PS), polyurethane (PU), Polyamide (PA), Polyethylene terephthalate (PET) and Polyvinyl chloride (PVC) in the landfill, and their abundance ranged from 0 to 80 items/g. The MPs surface gradually faded, became rough and even yielded cracks and holes with the landfill depth and age increase. The tiny-size MPs (< 100 µm) were the most abundant and their amount significantly increased from 28.14% to 49.13% in SL and from 24.54% to 59.51% in NSL, respectively, while large-size MPs were significantly reduced from the top to the bottom. Lysinibacillus (0.21%~67.87%) and Bacillus (0.10%~67.00%) were the dominate PDMs in SL and Candidatus_Caldatribacterium (5.06%~73.48%) was the dominate in NSL. The PE degradation was closely related to Candidatus_Cloacimonas (r = 0.688*) and Candidatus_Caldatribacterium (r = 0.680*); PS and PA were closely related to Candidatus_Contubernalis (r = 0.595*~0.705*) and PVC was closely related to Candidatus_Caldatribacterium (r = 0.547*). In addition to physical and chemical effects, biological effects can also promote the MPs formation in MSWLs.