Efficient Biodegradation of Low-density Polyethylene by Cyanobacteria Isolated from Submerged Polyethylene Surface in Domestic Sewage Water

Two dominant cyanobacterial species, Phormidium lucidum and Oscillatoria subbrevis, isolated from submerged polyethylene carry bags in domestic sewage water were found to be capable of degrading low-density polyethylene (LDPE) sheets efficiently. The FT-IR, SEM, NMR, CHN content, thermal, and tensile strength of PE were monitored for structural, morphological, and chemical changes of PE. The CHN analysis corroborated about 4% carbon utilization by the cyanobacterial species from the PE. The rapid growth of cyanobacterial species on the PE surface suggested that the microorganisms continued to gain energy from the PE. The reduction in lamellar thickness, weight, and crystallinity of the cyanobacterial-treated PE pointed to an efficient biodegradation process without any pro-oxidant additives or pretreatment. Alteration in bond indices computed from FT-IR spectroscopy revealed changes in functional group and side chain features indicating biodegradation. The enhanced laccase and manganese peroxidase activity corroborated the biodegradation. The C-NMR spectroscopy of the PE is consistent with short branching providing further evidence of biodegradation. Scanning electron microscopy and optical microscopy exhibited large grooves on the surface suggesting significant disruption of polyethylene structure.