Myco-remediation of plastic pollution: current knowledge and future prospects

Comparative evaluation of the impacts of different microplastics on greenhouse gas emissions, microbial community structure, and ecosystem multifunctionality in paddy soil

Although the increasing accumulation of microplastics (MPs) in terrestrial soil ecosystems has aroused worldwide concern, research remains limited on their potential impacts on soil processes and ecosystem functionality. Here, through a 41-day microcosm experiment, we found that polylactic acid (PLA), low-density polyethylene (LDPE), and polypropylene (PP) MPs consistently increased soil carbon nutrients and pH but had varying effects on soil nitrogen nutrients and the chemodiversity of dissolved organic matter (DOM). Different treatments led to notable shifts in the α-diversity and composition of soil microbial community, with phyla Proteobacteria and Ascomycota consistently enriched by MPs regardless of polymer type. The emissions of CO2 and N2O were suppressed by MPs in most cases, which in combination led to a decline in global warming potential. LDPE and 1 - 1.5 % of PLA MPs significantly improved the multifunctionality of the soil ecosystem, while PP and 0.5 % of PLA MPs exerted an opposite effect. Soil total organic carbon, pH, DOM molecular mass and condensation degree, and CO2 emissions were identified as the most important variables for predicting soil ecosystem multifunctionality. Results of this study can extend the current understanding of the impacts of MPs on soil biogeochemical cycling and ecosystem functionality.

Biodegradation: the best solution to the world problem of discarded polymers

The widespread use of polymers has made our lives increasingly convenient by offering a more convenient and dependable material. However, the challenge of efficiently decomposing these materials has resulted in a surge of polymer waste, posing environment and health risk. Currently, landfill and incineration treatment approaches have notable shortcomings, prompting a shift towards more eco-friendly and sustainable biodegradation approaches. Biodegradation primarily relies on microorganisms, with research focusing on both solitary bacterial strain and multi-strain communities for polymer biodegradation. Furthermore, directed evolution and rational design of enzyme have significantly contributed to the polymer biodegradation process. However, previous reviews often undervaluing the role of multi-strain communities. In this review, we assess the current state of these three significant fields of research, provide practical solutions to issues with polymer biodegradation, and outline potential future directions for the subject. Ultimately, biodegradation, whether facilitated by single bacteria, multi-strain communities, or engineered enzymes, now represents the most effective method for managing waste polymers.

Microplastics affect soil-plant system: Implications for rhizosphere biology and fitness of sage (Salvia officinalis L.)

A mesocosm experiment was set-up to investigate the effects of low-density polyethylene (LDPE) fragments deriving from plastic film on soil ecology, rhizosphere and plant (Salvia officinalis L.) fitness. The internal transcribed spacer (ITS) and 16S metagenomic analysis was adopted to evaluate taxonomic and functional shifts of both soil and rhizosphere under the influence of microplastics (MPs). Photosynthetic parameters and enzymes involved in oxidative stress were assessed to unveil the plant physiological state. MP fragments were analysed by scanning electron microscope (SEM) and metagenomics to investigate the plastisphere. Microbial biomarkers of MPs pollution were identified in soil and rhizosphere, reinforcing the concept of molecular biomonitoring. Overall, Bacillus, Nocardioides and Streptomyces genera are bacterial biomarkers of MPs pollution in soil whereas Aspergillus, Fusarium and Trichoderma genera, and Nectriaceae family are fungal biomarkers of MPs polluted soil. The data show that the presence of MPs promotes the abundance of taxa involved in the soil N cycle, but simultaneously reduces the endophytic interaction capability and enhances pathogen related functions at the rhizosphere level. A significant decrease in chlorophyll levels and increase of oxidative stress enzymes was observed in plants grown in MPs-polluted soil. The SEM observations of MPs fragments revealed a complex colonisation, where bacteria (Bacillus in MPSo and Microvirga in MPRz) and fungi (Aspergillus in MPSo and Trichoderma in MPRz) represent the main colonisers. The results demonstrate that the presence of MPs causes changes in the soil and rhizosphere microbial community and functions leading to negative effects on plant fitness.