Logeshwaran Panneerselvan

The global surge in plastic pollution, particularly from microplastics (MPs), has raised concerns about long-term implications for terrestrial and aquatic ecosystems. In response, biodegradable plastics are widely considered promising replacements for conventional plastics and are often marketed under labels such as “bio-based,” “biodegradable,” “compostable,” and “eco-friendly.” However, growing evidence suggests that the mismanagement of these materials contributes to the formation of microplastics derived from biodegradable plastics, which may pose ecological hazards depending on material composition and exposure conditions. This review integrates evidence on environmental fate and ecotoxicological effects with bioplastic formulation chemistry, including intentionally added substances, non-intentionally added substances and polymer degradation products. It links material composition and chemical release to biological responses, and highlights uncertainties in distinguishing particle-associated effects from chemical-mixture toxicity. The synthesis examines effects on soil properties, microbial and mesofaunal communities, and aquatic organisms, considering the limitations of extrapolating experimental findings to environmental exposure. This review identifies key knowledge gaps and emerging risks, challenging the perception that all biodegradable plastics are inherently environmentally benign. It highlights the need for regulatory oversight, standardized definitions, and transparent labelling to ensure that biodegradability claims align with real-world degradation conditions. Without sustainable end-of-life strategies, bioplastics may shift rather than solve the microplastic crisis. This work underscores the need for a precautionary approach to biopolymer development, grounded in life cycle thinking and ecological safety.

Bioaugmentation effectively enhances microbial bioremediation of hazardous polycyclic aromatic hydrocarbons (PAHs) from contaminated environments. While screening for pyrene-degrading bacteria from a former manufactured gas plant soil (MGPS), the mixed enrichment culture was found to be more efficient in PAHs biodegradation than the culturable pure strains. Interestingly, analysis of 16S rRNA sequences revealed that the culture was dominated by a previously uncultured member of the family Rhizobiaceae. The culture utilized C1 and other methylotrophic substrates, including dimethylformamide (DMF), which was used as a solvent for supplementing the culture medium with PAHs. In the liquid medium, the culture rapidly degraded phenanthrene, pyrene, and the carcinogenic benzo(a)pyrene (BaP), when provided as the sole carbon source or with DMF as a co-substrate. The efficiency of the culture in the bioremediation of PAHs from the MGPS and a laboratory waste soil (LWS) was evaluated in bench-scale slurry systems. After 28 days, 80% of Σ16 PAHs were efficiently removed from the inoculated MGPS. Notably, the bioaugmentation achieved 90% removal of four-ringed and 60% of highly recalcitrant five- and six-ringed PAHs from the MGPS. Likewise, almost all phenanthrene, pyrene, and 65% BaP were removed from the bioaugmented LWS. This study highlights the application of the methylotrophic enrichment culture dominated by an uncultured bacterium for the efficient bioremediation of PAHs.

Pyroligneous acid (PA) is often used in agriculture as a plant growth and yield enhancer. However, the influence of PA application on soil microorganisms is not often studied. Therefore, in this study, we investigated the effect of PA (0.01–5% w/w in soil) on the microbial diversity in two different soils. At the end of eight weeks of incubation, soil microbial community dynamics were determined by Illumina-MiSeq sequencing of 16S rRNA gene amplicons. The microbial composition differed between the lower (0.01% and 0.1%) and the higher (1% and 5%) concentration in both PA spiked soils. The lower concentration of PA resulted in higher microbial diversity and dehydrogenase activity (DHA) compared to the un-spiked control and the soil spiked with high PA concentrations. Interestingly, PA-induced plant growth-promoting bacterial (PGPB) genera include Bradyrhizobium, Azospirillum, Pseudomonas, Mesorhizobium, Rhizobium, Herbaspiriluum, Acetobacter, Beijerinckia, and Nitrosomonas at lower concentrations. Additionally, the PICRUSt functional analysis revealed the predominance of metabolism as the functional module’s primary component in both soils spiked with 0.01% and 0.1% PA. Overall, the results elucidated that PA application in soil at lower concentrations promoted soil DHA and microbial enrichment, particularly the PGPB genera, and thus have great implications for improving soil health.