Biodeterioration of plasma pretreated LDPE sheets by Pleurotus ostreatus

PLoS One. 2018 Sep 13;13(9):e0203786. doi: 10.1371/journal.pone.0203786. eCollection 2018.

Abstract

Low-density polyethylene (LDPE) waste generates an environmental impact. To achieve the most suitable option for their degradation, it is necessary to implement chemical, physical and biological treatments, as well as combining procedures. Best treatment was prognosticated by Plackett-Burman Experimental Design (PB), evaluating five factors with two levels (0.25 mM or 1.0 gL-1 glucose, 1.0 or 2.0 mM CuSO4, 0.1 or 0.2 mM ABTS [2, 20-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid)], pH 4.5 ± 0.2 or 7.0 ± 0.2 and 30 or 90 day incubation), which was reproduced for 150 days. Therefore, PB identified a sequential treatment (plasma followed by fungus) for partial LDPE biodeterioration. Sheets were pretreated with glow discharge plasma (O2, 3.0 x 10(-2) mbar, 600 V, 6 min.), followed by Pleurotus ostreatus biodeterioration. Fungus growth, colonization percentage, and pigment generation followed. Laccase (Lac), manganese peroxidase (MnP) and lignin peroxidase (LiP) activities were appraised. Additionally, contact angle (CA), functional group presence and changes and carbonyl and vinyl indices (Fourier transformed infrared spectroscopy) were evaluated. LDPE surface changes were assessed by Young's modulus, yield strength, scanning electronic microscopy (SEM), Fourier transformed infrared spectroscopy (FTIR) and atomic force microscopy (AFM). Plasma discharge increased hydrophilicity, decreasing CA by 76.57% and increasing surface roughness by 99.81%. P. ostreatus colonization was 88.72% in 150 days in comparison with untreated LDPE (45.55%). After this treatment carbonyl groups (C = O), C = C insaturations, high hydrophilicity CA (16 ± 4) °, and low surface roughness (7 ± 2) nm were observed. However, the highest Lac and LiP activities were detected after 30 days (Lac: 2.817 U Lac g-1 and LiP: 70.755 U LiP g-1). In addition, highest MnP activity was observed at day 120 (1.097 U MnP g-1) only for P. ostreatus treated LDPE. Plasma favored P. ostreatus adsorption, adherence, growth and colonization (88.72%), as well as partial LDPE biodeterioration, supported by increased hydrophilicity and presence of specific functional chemical groups. The approximate 27% changes in LDPE physical properties support its biodeterioration.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biodegradation, Environmental*
  • Hydrophobic and Hydrophilic Interactions
  • Materials Testing
  • Microscopy, Electron, Scanning
  • Oxidation-Reduction
  • Plasma Gases*
  • Pleurotus* / growth & development
  • Pleurotus* / metabolism
  • Polyethylene* / chemistry
  • Spectroscopy, Fourier Transform Infrared
  • Surface Properties
  • Time Factors
  • Viscoelastic Substances / chemistry

Substances

  • Plasma Gases
  • Viscoelastic Substances
  • Polyethylene

Associated data

  • figshare/10.6084/m9.figshare.6199295

Grant support

This work was financed by “Pontificia Universidad Javeriana Bogotá, D.C. Colombia”; as part of grant ID: 00006736, titled “Transformación de polietileno de baja densidad (LDPE) por medio de ablación con plasma y actividad enzimática de Pleurotus ostreatus”.