Characterization of Microbial Communities during Bioplastics Degradation in Mesophilic and Thermophilic Composting Conditions

Conventional petroleum-based plastics are non-degradable materials that are difficult to degrade during disposal and landfill after use; therefore, they have an adverse environmental impact over a long period of time. An example is the problem of soil landfill of agricultural mulching films, which are discarded after agricultural activities. Plastic particles alter the physicochemical properties of the soil, resulting in reduced crop yields and disruption of nutrient cycling within the soil ecosystem, while also impacting groundwater contamination. Furthermore, they serve as carriers for organic pollutants such as heavy metals, pesticides, and herbicides, causing greater environmental contamination. To solve this problem, there has been a growing interest in bioplastics as alternatives to conventional fossil-based plastics, particularly in the agricultural field. In order to reduce the pollution load in the soil through the utilization of bioplastics, it is essential to thoroughly understand the microorganisms involved in biodegradation and their corresponding biodegradation characteristics within soil and compost environments. Therefore, in this study, microbial communities were characterized during the degradation of two bioplastics (Polylactic acid (PLA) and Polybutylene adipate terephthalate (PBAT)), under mesophilic (35℃) and thermophilic (58℃) composting conditions. PLA and PBAT films and granules were buried in chicken manure compost, and the biodegradability was assessed based on the weight loss over time. PLA film was degraded rapidly, by 41.5% in 5 days and by 91.15% in 10 days under thermophilic composting conditions, and completely degraded in 15 days. Under mesophilic composting conditions, PLA film showed a degradation rate of 17.9% in 20 days. To characterize microbial communities during the bioplastics degradation, compost samples near the bioplastics were collected, followed by DNA extraction. The 16S rRNA gene region was amplified using the 515F/806R primer set to investigate the bacterial community, as well as the ITS2 gene region using the ITS3/ITS4 primer set to analyze the fungal community. Subsequently, the sequences were analyzed using Illumina Miseq. The information obtained in this study can be used to secure promising bioresources to enhance bioplastics degradation.