Biodegradability of Low Density Polyethylene (LDPE) and Discovery of LDPE-Degrading Microbes

Three types of low density polyethylene (LDPE)-degrading microbes were discovered, and unambiguous evidence for biodegradation of LDPE was presented. Pieces of LDPE film, buried and biodegraded, and their surrounding soil were used as the source of microbes. Powder of a photo-degraded and antioxidant-free LDPE film was added as the sole source of carbon in the liquid medium. From the medium that underwent enriched cultivation, three strains of microbes were separated. They were classified on the basis of LDPE-degrading capabilities, confirmed by -OH generation and degradation traces. Using “Bergey's Manual of Determinative Bacteriology”, the genuses of the microbes were identified as Bacillus circulans, Bacillus brevies, Bacillus sphaericus, which belong among the natto bacteria, common in soil. Their degrading ability was confirmed on LDPE film previously photo-degraded by outdoor exposure for six weeks. After three months of cultivation, we identified the existence of body marks on the film surface, which are characteristic of microbial biodegradation.