Author(s)

Dinesh Adhikari, Masaki Mukai, Kenzo Kubota, Takamitsu Kai, Nobuyuki Kaneko, Kiwako S. Araki, Motoki Kubo^*

Department of Biotechnology, Faculty of Life Sciences, Biwako-Kusatsu Campus, Ritsumeikan University, Kusatsu, Shiga, Japan.

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.

Bioplastics, Biodegradation, Soil Microorganisms, Bacterial Diversity

Adhikari, D., Mukai, M., Kubota, K., Kai, T., Kaneko, N., Araki, K.S. and Kubo, M. (2016) Degradation of Bioplastics in Soil and Their Degradation Effects on Environmental Microorganisms. Journal of Agricultural Chemistry and Environment, 5, 23-34. doi: 10.4236/jacen.2016.51003.