Decay of low-density polyethylene by bacteria extracted from earthworm's guts: A potential for soil restoration

TLDR

Low‑density polyethylene is the most abundant microplastic worldwide, and passage through the gut of the earthworm *Lumbricus terrestris* increases its decay and reduces particle size. This study examined whether gut bacteria from *L. terrestris* contribute to LDPE microplastic degradation. Gram‑positive Actinobacteria and Firmicutes isolated from the worm’s gut were inoculated into gamma‑sterilized soil microcosms with or without LDPE microplastics to assess their effect.

Abstract

Low-density polyethylene (LDPE) is the most abundant source of microplastic pollution worldwide. A recent study found that LDPE decay was increased and the size of the plastic was decreased after passing through the gut of the earthworm Lumbricus terrestris (Oligochaeta). Here, we investigated the involvement of earthworm gut bacteria in the microplastic decay. The bacteria isolated from the earthworm's gut were Gram-positive, belonging to phylum Actinobacteria and Firmicutes. These bacteria were used in a short-term microcosm experiment performed with gamma-sterilized soil with or without LDPE microplastics (MP). We observed that the LDPE-MP particle size was significantly reduced in the presence of bacteria. In addition, the volatile profiles of the treatments were compared and clear differences were detected. Several volatile compounds such as octadecane, eicosane, docosane and tricosane were measured only in the treatments containing both bacteria and LDPE-MP, indicating that these long-chain alkanes are byproducts of bacterial LDPE-MP decay.