Degradation of Oxo-Degradable-Polyethylene and Polylactic Acid Films Embodied in the Substrate of the Edible Fungus Pleurotus ostreatus

Abstract

Degradable plastic mulch is being used to overcome the negative environmental impacts of burning and landfilling agricultural plastic waste. In this study P. ostreatus was used to model the capacity of a vegetal species to degrade conventional and degradable plastic films. Plastics studied were oxo-degradable polyethylene (OXO-PE), UV-irradiated oxo-degradable polyethylene (UV-OXO-PE), polylactic acid (PLA) and conventional polyethylene (C-PE). The cultivation of P. ostreatus resulted in a reduction in the median of weight (78.2% - 80.2%) and volume (56.1% - 60.1%) of the substrate (wheat straw). Degradation of the plastics embodied was evidenced by a reduction in the median of the elongation at break (OXO-PE 475% to 109%, UV-OXO-PE 23% to 8%, PLA 596% to 398% and C-PE 505% to 304%) and an increase in the median of the carbonyl index (OXO-PE 0.062 to 0.114, UV-OXO-PE 0.098 to 0.145 and PLA 0.024 to 0.034). The Kruskal-Wallis test found no statistical difference (p = 0.384) between the medians of the biological efficiency for substrates containing plastics and the substrate without plastic. In conclusion, plastics embodied in the substrates used for cultivation of P. ostreatus are degraded and the degradation of these plastics does not affect the short term growth of P. ostreatus.