Study on Biodegradation of Sun Treated Low-Density Polyethylene (Ld-PE) Films by Plastic Degrading Bacteria in Bioreactors

Accumulation of polyethylene (PE) wastes has become a major environmental problem. The objective of this research was to assess the potential for microbial degradation of sun-treated low-density PE as a natural way to eliminate PE wastes in semi-industrial condition. Low-density polyethylene (LDPE) films were exposed to one month of sun radiation treatment and then cultured with two PE-degrading bacteria (Sphigobacterium moltivorum IRN11 and Delftia tsuruhatensis IRN27) in aerobic bioreactors over 100 days. Weight loss percentage of the PE and the culture pH were measured. Also, Changes in the chemical structure of the LDPE were assessed by FT-IR and surface erosion and microbial layer formation by bacterial activity was observed by Scanning Electron Microscopy. Partial increases in the culture pH were recorded during the incubation period. The weight loss percentage for T-LDPE samples cultured with Sphigobacterium moltivorum IRN11 and Delftia tsuruhatensis IRN27 was 3.31%±0.013 and 3.98%±0.025 in TLDPE samples, respectively, and functional carbonyl-groups in the TLDPE samples decreased significantly due to bacterial hydrolysis. SEM images showed the different microbial layer formation on sun-treated low-density polyethylene (T-LDPE) for both bacteria. Our results suggest that exposure of LDPE to sun radiation had a significant effect on biodegradation of Ld-PE films and that the two bacteria tested were able to enhance the biodegradation the T-LDPE.