Degradation of Green Polyethylene by Pleurotus ostreatus

Abstract

We studied the biodegradation of green polyethylene (GP) by Pleurotus ostreatus. The GP was developed from renewable raw materials to help to reduce the emissions of greenhouse gases. However, little information regarding the biodegradation of GP discarded in the environment is available. P. ostreatus is a lignocellulolytic fungus that has been used in bioremediation processes for agroindustrial residues, pollutants, and recalcitrant compounds. Recently, we showed the potential of this fungus to degrade oxo-biodegradable polyethylene. GP plastic bags were exposed to sunlight for up to 120 days to induce the initial photodegradation of the polymers. After this period, no cracks, pits, or new functional groups in the structure of GP were observed. Fragments of these bags were used as the substrate for the growth of P. ostreatus. After 30 d of incubation, physical and chemical alterations in the structure of GP were observed. We conclude that the exposure of GP to sunlight and its subsequent incubation in the presence of P. ostreatus can decrease the half-life of GP and facilitate the mineralization of these polymers.

Plastics Polymers Degradation by Fungi

“…However, after 4 months of exposure to sunlight we did not observe any fragmentation of the plastic bags, only the appearance of small cracks and the bleaching of the film were observed (Figure 2). Da Luz et al [14,15] also showed changes in mechanical properties of oxo-biodegradable and green polyethylene after 120 days of exposure to sunlight. According to them, this time of exposure is insufficient for other physical or chemical changes, concluding that the mechanical properties alterations, such as the reduction of breaking energy and elasticity facilitated the fungal colonization of plastic waste.…”

“…In this micrograph, the red arrows show hyphae in plastic waste after 60 days of exposure to sunlight and 30 days of incubation. Da Luz et al [13][14][15] showed the formation of mycelium on the surface of d2w plastic and green polyethylene with different time of exposure to sunlight and of fungal incubation. They also reported the morphological characteristics of the mycelia of P. ostreatus PLO6.…”

“…So, these polymers when exposed to ultraviolet light or at high temperatures are cleaved in low molecular mass compounds that are assimilated by microorganisms [8]. Several studies have shown the biodegradable plastics degradation, after exposed to ultraviolet light or heat, by bacteria and fungi [10][11][12][13][14][15][16].…”

“…The plastic bags of green polyethylene are produced using low-density polyethylene (LDPE) and green polymers obtain of sugarcane [17]. We have showed the green polyethylene degradation by Pleurotus ostreatus PLO6 [15]. However, little information regarding to the biodegradation of these bags is available.…”

“…This fungus has also been used in the bioconversion of agricultural residues, in biodegradation of organic pollutants, xenobiotics, and industrial effluents, in the cellulose bleaching and production of food and enzymes [23][24][25]. We showed that P. ostreatus PLO6 are capable to degrade oxo-biodegradable plastics and green polyethylene [13][14][15]. Furthermore, this fungus form edible mushroom that is source of proteins, fibers, minerals and carbohydrates.…”