Oxo-Biodegradation of Polyethylene by Pseudomonas Aeruginosa
Pro-oxidants accelerate abiotic oxidation and consequently, polymer chain cleavage rendering the product more susceptible to biodegradation. The present paper reports a study in which the oxo-biodegradation of a recalcitrant polyethylene and oxo-biodegradable polyethylene (polyethylene with pro-oxidant) was investigated in two stages. The first stage of abiotic oxidation was carried out in an air circulated oven to simulate the effect of compost environment. The second stage of biodegradation was studied in the presence of a selected micro-organism i.e. Pseudomonas Aeruginosa. The progress of degradation was followed by monitoring the physical and chemical changes of the samples using tensile strength and elongation tests, high-temperature gel permeation chromatography (GPC), and infrared spectroscopy (FTIR). The growth of bacteria on the surface of the polymer was monitored using environmental scanning electron microscopy (ESEM).
Molecular weight distribution data obtained from GPC shows that abiotic oxidation has significant effect on oxo-biodegradable polyethylene but not on polyethylene. Also, abiotic oxidation has enhanced and accelerated the biodegradability of oxo-biodegradable polyethylene due to the formation of low molecular weight compounds that are more susceptible to biotic reactions. However, all the samples were observed to have colonies of micro-organisms. It has been also observed that the film surface in the vicinity of the micro-organisms is eroded. The decay of oxidation products on the polymer film surface was monitored using FTIR. The presence of protein and polysaccharides on the surface indicates that the micro-organisms are growing by consuming original oxidation products such as ketones, esters and lactones