Biodegradation of bioplastic polycaprolactone by marine bacterium Alteromonas sp. ghpt-2 and its adaptive responses

Biodegradable plastics have been developed and applied over the past thirty years, and their biodegradation has drawn much attention. In this study, the marine bacterium Alteromonas sp. ghpt-2 was identified to degrade polycaprolactone (PCL) effectively. The optimized degradation conditions were temperature 15 °C, pH 8.0, carbon source of maltose and NaCl concentration of 0-3 %, resulting in enhancing the degradation rate to 9.25 %. The alteration of PCL film was represented after bacterial degradation by differential scanning calorimetry (DSC), fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). After incubation with PCL, the metabolic pathways of strain ghpt-2 were downregulated including ribosome, Tricarboxylic Acid (TCA) cycle, glyoxylate and dicarboxylate metabolism, etc., which affected the cell growth and multiplication. In contrast, the upregulated nitrogen metabolism and ATP-Binding Cassette (ABC) transporters pathway relieved the PCL stress and maintained the bacterial growth. By metabolic pathways analysis, the PCL biodegradation process was proposed including biofilm formation, biodeterioration and assimilation. In this study, a low-temperature and NaCl-tolerant PCL degrading bacterium was obtained that could be applied in the treatment of plastic waste, including the adversity of cold and high salinity.