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Poly(L-lactide) mineralisation under environmental conditions is enhanced in earthworm guts
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Scientists found that earthworms can help break down PLLA, a "biodegradable" plastic often used in food packaging and other products, much faster than it would break down in soil alone. This matters because biodegradable plastics don't always live up to their name in real-world conditions, and understanding how nature can help clean them up could reduce the amount of plastic pollution (including microplastics) that ends up in our soil, water, and eventually our food supply.
Microplastic accumulates in various habitats, posing a potential environmental threat. Biodegradable polymers like poly(L-lactide) (PLLA) is a possible eco-friendly alternative to conventional, non-biodegradable plastics. However, biodegradation of PLLA in soil is strongly limited, but is potentially enhanced by soil-dwelling organisms. We recently showed that PLLA exposure positively affected reproduction in the earthworm Eisenia fetida, and increased gut lactate concentrations, indicating the hypothesis of earthworm-enhanced PLLA biodegradation. 13C-labelled PLLA was used for a 13CO2-tracing approach to monitor PLLA mineralisation in presence and absence of the earthworm E. fetida. Mineralisation of 0.2% of initial PLLA was attributed to the activity of earthworms after two weeks of exposure. Extrapolation assuming zero-order kinetics and limitation of microbial growth suggested a substantially shorter half-life of PLLA in earthworm-amended soils. This finding provides strong evidence that conditions inside the earthworm gut are beneficial for PLLA degradation and provide a basis for the development of mitigation strategies for PLLA microplastic pollution.
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Polylactic acid degradation is enhanced by microbial processes in earthworm guts
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Polylactic acid (PLA), a compostable bioplastic, was found to degrade more rapidly when it passes through earthworm guts due to microbial activity in the earthworm digestive system. This suggests that earthworms may play a role in accelerating the breakdown of biodegradable plastics in soil. However, if PLA degrades incompletely it could still generate microplastic fragments, so biodegradability claims need to be evaluated under realistic soil conditions.
Earthworms’ Degradable Bioplastic Diet of Polylactic Acid: Easy to Break Down and Slow to Excrete
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Researchers found that earthworms preferred ingesting both PET and PLA microplastics over clean soil, but bio-based PLA was more easily broken down in their guts while being excreted more slowly than fossil-based PET, raising concerns about bioplastic accumulation in soil organisms.
Fragmentation and depolymerization of microplastics in the earthworm gut: A potential for microplastic bioremediation?
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Researchers explored whether earthworms can break down microplastics in soil by passing them through their digestive systems. They found that earthworms fragmented and partially broke down polyethylene and biodegradable plastic particles, reducing their size and altering their chemical structure. This suggests earthworms could play a role in naturally reducing microplastic contamination in soil, though more research is needed to understand whether the smaller fragments pose their own risks.
Decay of low-density polyethylene by bacteria extracted from earthworm's guts: A potential for soil restoration
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Researchers isolated bacteria from earthworm guts that were able to degrade low-density polyethylene, demonstrating that intestinal microbes from soil invertebrates may play a role in plastic breakdown. The findings suggest that earthworm gut microbiomes are a reservoir of plastic-degrading bacteria with potential applications for bioremediation of LDPE-contaminated soils.
Potential Use of Earthworms to Enhance Decaying of Biodegradable Plastics
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Researchers examined the potential of earthworms to accelerate the biodegradation of both conventional and biobased biodegradable plastics in soil, finding that earthworm activity can enhance the physical fragmentation and microbial degradation of some polymers, though effectiveness varies significantly by polymer type. The study suggests earthworm-assisted composting as a partial strategy to reduce agricultural plastic pollution.
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When a large batch of papers lands in the Atlas, we read through it and send a short write-up of what stood out.