Temperature-dependent mulch film degradation behavior on compost and isolation of bioplastic degrading compost microorganisms

The petrochemical plastics have been mentioned as a major cause of the environmental pollution. To alter the fossil fuel-based plastics, bioplastics has been arising as an alternative, promising a sustainable recycle of natural resources. Focusing on the importance of bioplastic in agriculture, this study investigated the degradation behavior of biodegradable mulch film (BDM) on the compost at five different temperatures, ranging from psychrophilic to thermophilic. Separately, the biotic effect of the compost on the BDM degradation was examined by isolating BDM degrading compost microorganisms. A rapid decomposition emerged at 30 °C and 45 °C, supporting the hypothesis that the high temperature enhances BDM degradation. Scanning Electron Microscopy (SEM) inspection could not deliver details of film morphology due to the biofilm and compost rest remaining on the BDM surface. The changes of material’s physical property also supported the positive relation between BDM degradation rate and temperature. A rapid loss of BDM tensile strength and flexibility was observed proportional to the incubation temperature. The chemical and thermodynamical property during the material degradation could not be adequately interpretated due to the interference of compost on BDM. A constant proliferation of biofilm was perceived over time in the form of compost and microbial accumulation on the BDM surface. The positive effect of mechanical stress on the biotic degradation was estimated. Through the enrichment culture and 16S/18S ribosomal deoxyribonucleic acid (rDNA) sequencing, 7 compost microorganisms were isolated and identified as potential BDM degraders. The ability to degrade BDM by the isolates was assessed based on the known hydrolases from other studies. A strong demand for the sample wash method development was discussed in the end of the study. A requirement to development of an adequate method to collect biofilm from the BDM is mentioned. The application of quantitative polymerase chain reaction (qPCR) and microbial community sequencing was suggested to examine the compost’s biotic effect to the BDM degradation. This study emphasizes the multidisciplinary investigation on bioplastics. A profound understanding of both bioplastic material and microbial bioplastic utilization could synergistically improve the development of novel bioplastic concerning its’ life cycle in the natural resource management.