Bioplastic Degradation Potential of Microorganisms Isolated from the Soil

Abstract

Plastic disposal is among the utmost problems threatening the environment at present, as enormous quantities of synthetic plastics are non-degradable. A constant exploration for bioplastic degraders is needed due to increasing demands for sustainable waste treatments. Bioplastic (Polycaprolactone) degradation potential of microorganisms isolated from soil was assessed. Soil sample was collected from a plastic dump site in Trans-Amadi, Port Harcourt, Nigeria. Isolation of Polycaprolactone (PCL) degrading bacteria and fungi were carried out via enrichment procedure and clear zone technique. Morphological, biochemical and molecular characteristics were used for strain identification of isolates. The optimal conditions for PCL degradation by bacterial and fungal strains were evaluated by growing the isolates at different temperatures (25, 30, 35 and 40°C), medium pH (ranging from pH 4 to 8) and salinities (5, 10, 15 and 20 ppt.) for 15 days. PCL residual weight in the culture was measured and used for PCL degradation assessment. Three PCL degrading bacterial strains (Bacillus megaterium, Alcaligenes aquatilis and Shewanella haliotis) and one fungal strain (Filobasidium uniguttalatum) were isolated. PCL maximum degradation rate of 59%, 56% and 53% respectively for bacterial strains and 62% for fungal strain were observed at 30°C. PCL maximum degradation rate of 63% for Filobasidium uniguttalatum were observed at pH 5 while the maximum degradation rate of 60% for Bacillus megaterium, 54% for Alcaligenes aquatilis and 57% for Shewanella haliotis were observed at pH 7. PCL maximum degradation rate of 58% for Bacillus megaterium, 55% for Alcaligenes aquatilis, 52% for Shewanella haliotis and 62% for Filobasidium uniguttalatum were observed at salinity of 5 ppt. It is concluded that the potential of the isolated indigenous microbial strains to degrade PCL qualifies them for use as compost cultures in waste treatment of bioplastic.