Screening of microorganisms from compost of the Smokey Mountain for the presence of low density polyethylene-degrading activities

• Main Author: Zabal-Dungca, Julieta C.
• Format: text
• Language: English
• Published: Animo Repository 2004
• Subjects: Compost; Microorganisms; Polyethylene; Biology
• Online Access: https://animorepository.dlsu.edu.ph/etd_doctoral/1197; https://animorepository.dlsu.edu.ph/context/etd_doctoral/article/2198/viewcontent/CDTG003788_P.pdf
• Institution: De La Salle University

Microorganisms isolated from the Smokey Mountain abandoned dumpsite were screened for the presence of low density polyethylene (LDPE)-degrading activities. Degradation was monitored after 60 and 180 days of incubation in terms of the changes on surface morphology using Scanning Electron Microscope, and changes in the mechanical properties using the Thermal Mechanical Analyzer. LDPE films that showed remarkable crumple and perforations were further analyzed for changes on their thermal properties using the Differential Scanning Calorimetry and possible functionalization of the film using the Fourier Transform Infra Red Spectroscopy. Five mixed cultures were able to degrade the LDPE films as shown by the pronounced crumple and appearance of microcracks and perforations on the film surface as compared to the control LDPE films that were not exposed to the cultures. Such changes on the gross morphology was confirmed using SEM. Degradation of LDPE did not produce pronounced changes on the mechanical and thermal properties of the LDPE films. Results of FT-IR did not show a new functional group but suggest free radical mechanism. The conditions for an effective LDPE-degrading activities were optimized using two mixed cultures showing positive degradation, at different pHs (5, 7 and 8) at different temperatures (24 0C, 37 0C and 42 0C), and at different cell densities (9 X 108 , 1.2 X 109 and 1.5 x 109 cells ml-1). Results showed that LDPE degradation was optimal at pH 8, temperature of 37 0C and cell density of 1.5 x 109 cells ml-1. Microorganisms that were found to possess LDPE-degrading activities were identified to be the bacteria Micrococcus luteus, Micrococcus varians, Bacillus cereus, and Chryseomonas luteola, and the fungi Aspergillus fumigatus, Aspergillus oryzae, Penicillium sp. and Radiomyces sp.