Bacterial Dynamics During the Degradation of Starch-based Bioplastic and Oxo- degradable Plastic in Compost Soil

Abstract Background: Plastic waste accumulation is one of the main ecological concerns in the past decades. A new generation of plastics that are easier to degrade in the environment compared to conventional plastics, such as starch-based bioplastic and oxo-degradable plastic, is perceived as a solution to this issue. However, the main degraders of such materials and their fate in the environment are unclear. In this study, we monitored the dynamics of bacterial community in soil upon introduction of commercial starch-based bioplastic and oxo-degradable plastic. The plastics were buried separately in compost soil and incubated for 30, 60, 90, and 120 days. Following incubation, soil pH and temperature as well as the weight of remaining plastics were measured. Bacterial diversity in soil surrounding the plastics was analyzed using Illumina high-throughput sequencing of the V3-V4 region of 16SrDNA. Results: Starch-based bioplastic degraded quicker than oxo-degradable plastic in soil. The bacterial composition in soil fluctuated over time with or without the introduction of either type of plastic. While the major bacterial phyla remained similar for all treatment in this study, different types of plastics led to different soil bacterial community structure. None of these bacteria were abundant continuously, but rather they emerged at specific time points. The introduction of plastics into soil increased not only the population of bacteria with the ability to directly utilize plastic component for their growth, but also the abundance of those that may interact with direct degraders. Interestingly, there were no specific genera that were prevalent throughout the burial period. Conclusions: The degradation of both starch-based bioplastic and oxo-degradable plastic involves a complex set of bacteria that continues to shift over time.