Molecular analysis of fungal communities of biodegradable plastics in two Japanese soils

Abstract

This study aimed to elucidate the microbial communities responsible for the decomposition of poly-(ϵ-caprolactone) (PCL), poly-(butylene succinate) (PBS), poly-(butylene succinate and adipate) (PBSA) and poly-lactide (PLA) in two soils using a culture-independent, polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) method with subsequent sequencing of the main DGGE bands. The PCL, PBS and PBSA films were considerably degraded within 50 days at 25°C under upland dark conditions in one soil, while the PLA film was not degraded at all after 120 days in the soil. In the other soil, with less soil organic matter content, only the PBSA films showed any discernible degradation in the 50-day incubation. Many fungal hyphae and hollows along fungal hyphae were observed on the surface of those PCL, PBS and PBSA films. The PCR-DGGE patterns of fungal DNA that were extracted from the degrading plastic films were similar between the soils, with a few different bands, irrespective of the type of plastic film. All four sequenced DGGE bands belonged to Chaetothyriales or Ascomycota incertaesedis in Ascomycota. All the fungal isolates, a total of 60 colonies, formed either white or yellow colonies on Rose Bengal agar medium with similar appearance, and four representative isolates, two white and two yellow isolates from PCL and PBSA films, showed the same mobility on DGGE gel to the mobility of a common band of DNA extracts. Their closest relatives were Penicillium spp.