Biodeterioration of plasma pretreated LDPE sheets by Pleurotus ostreatus

• Published in: PloS one 2018-09, Vol.13 (9), p.e0203786-e0203786
• Main Authors: Gómez-Méndez, Luis D, Moreno-Bayona, Diana A, Poutou-Piñales, Raúl A, Salcedo-Reyes, Juan C, Pedroza-Rodríguez, Aura M, Vargas, Andrés, Bogoya, Johan M
• Format: Article
• Language: English
• Subjects: Analysis; Atomic beam spectroscopy; Atomic force microscopy; Biodegradation; Biodeterioration; Biology and Life Sciences; Carbonyl groups; Carbonyls; Colonization; Contact angle; Design of experiments; Environmental aspects; Environmental impact; Enzymes; Experimental design; Fourier transforms; Functional groups; Fungi; Gene expression; Glow discharges; Hydrophilicity; Infrared spectroscopy; Laboratories; Laccase; Lignin; Lignin peroxidase; Low density polyethylene; Low density polyethylenes; Manganese; Manganese peroxidase; Mechanical properties; Microorganisms; Microscopy; Modulus of elasticity; Molecular weight; Organic chemistry; Oxidation-reduction reactions; Peroxidase; Physical properties; Physical Sciences; Physics; Plasma jets; Plasma physics; Pleurotus ostreatus; Polyethylene; Polymers; Properties; Research and Analysis Methods; Sewage treatment; Sheets; Spectroscopy; Surface roughness
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0203786

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.