TITLE:
Degradation of Bioplastics in Soil and Their Degradation Effects on Environmental Microorganisms
AUTHORS:
Dinesh Adhikari, Masaki Mukai, Kenzo Kubota, Takamitsu Kai, Nobuyuki Kaneko, Kiwako S. Araki, Motoki Kubo
KEYWORDS:
Bioplastics, Biodegradation, Soil Microorganisms, Bacterial Diversity
JOURNAL NAME:
Journal of Agricultural Chemistry and Environment,
Vol.5 No.1,
February
29,
2016
ABSTRACT: Degradation of three kinds of bioplastics and their effects on microbial biomass and microbial diversity
in soil environment were analyzed. The degradation rate of bioplastic in soil was closely
related to the main components in the bioplastics. Poly (butylene succinate)-starch (PBS-starch)
and poly (butylene succinate) (PBS) were degraded by 1% to 7% after 28 days in a soil with an initial
bacterial biomass of 1.4 × 109 cells/g-soil, however poly lactic acid (PLA) was not degraded in
the soil after 28 days. When the powdered-bioplastics were examined for the degradation in the
soil, PBS-starch also showed the highest degradability (24.4% degradation after 28 days), and the
similar results were obtained in the case of long-term degradation experiment (2 years). To investigate
the effect of bacterial biomass in soil on biodegradability of bioplastics, PBS-starch was buried
in three kinds of soils differing in bacterial biomass (7.5 × 106, 7.5 × 107, and 7.5 × 108 cells/g-soil).
The rate of bioplastic degradation was enhanced accompanied with an increase of the bacterial
biomass in soil. 16S rDNA PCR-DGGE analysis indicated that the bacterial diversity in the soil
was not affected by the degradation of bioplastics. Moreover, the degradation of bioplastic did not
affect the nitrogen circulation activity in the soil.