VOLUME 11 (Supplement)

by Denisse Yans Z. Dela Torre, Lee A. Delos Santos, Mari Louise C. Reyes and Ronan Q. Baculi^*

Department of Biology, College of Science, University of the Philippines Baguio,
     Baguio City, Philippines

Low-density polyethylene (LDPE), a commonly-used packaging material that is resistant to degradation under natural conditions, contributes to environmental pollution. Recently, considerable attention has been focused on microorganisms capable of degrading polyethylene-based plastic waste. In this study, bacterial strains with unique capabilities to use low-density polyethylene as sole carbon source were isolated from a hyperalkaline spring (pH 11) through enrichment culture procedures. The process of biodegradation was observed for 90 days in a synthetic medium containing LDPE films. The bacterial isolates, phylogenetically-affiliated with Bacillus krulwichiae, Bacillus pseudofirmus, Prolinoborus fasciculus, and Bacillus sp., were able to reduce the weight of the residual polymer up to 9.9%, 8.3%, 5.1%, and 6.3%, respectively. The viability of the isolates was correlated with an increased protein density of the biomass. SEM analysis revealed that the strains exhibited strong adhering capabilities as indicated by morphological changes that occurred on the surface of LDPE films incubated with bacterial isolates. Fourier transform infrared spectra showed changes in keto carbonyl index, ester carbonyl bond index, internal double bond index, and vinyl bond index supporting the depolymerization activity of the isolates. Reduction in percent crystallinity of the films incubated with isolates was also observed. This study confirmed the ability of the selected microorganisms to utilize LDPE as carbon source, and to degrade the films without thermal and oxidative pre-treatments.