Biodeterioration of plasma pretreated LDPE sheets by Pleurotus ostreatus

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.

Plastics Polymers Degradation by Fungi

“…In studies on the plastics degradation for P. ostreatus, the authors also observed chemical and physical changes similar to the observed in our study [29,30].…”

“…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. The chemical and physical changes in the low-density polyethylene (LDPE) was observed after pretreated of the LDPE sheets with low discharge plasma (O 2 , 3.0 × 10 −2 mbar, 600 V) for 6 minutes [29,30]. According to authors, this pretreated was important by plastics biodeterioration by P. ostreatus.…”

“…According to Da Luz et al [14], the low specificity of the lignocellulolytic enzymes and presence of pro-oxidant ions and endomycotic nitrogen-fixing microorganisms were the main reasons for the biotic degradation of oxo-biodegradable plastics. Gómez-Méndez et al, [29] observed activities of laccase, manganese peroxidase (MnP) and lignin peroxidase during P. ostreatus growth in plasma pretreated Low-density polyethylene (LDPE) sheets. These authors showed that LDPE biodeterioration was due to activities of these fungal enzymes.…”

Simultaneous bioconversion of lignocellulosic residues and oxodegradable polyethylene by Pleurotus ostreatus for biochar production, enriched with phosphate solubilizing bacteria for agricultural use

“…Plant and flower grower industries produce vast quantities of organic waste (bark, sawdust, leaves, stems, fragmented flowers, among others) containing high amounts of lignin, cellulose and hemicellulose [4–6]. In addition, these companies use low and high-density polyethylene (LDPE and HDPE) with different purposes: packing planting material, seedling rooting, mulching, greenhouse fabrication and wrapping of product [5,6].…”

“…To carry out simultaneous bioconversion of LCB and LDPE oxo different types of microorganisms can be used, by themselves, in co-cultures or in consortiums [15–17]. From an array of microorganisms studied, lignolytic white rot fungi are the most efficient to perform partial or total biotransformation of these types of solid residues [16–19] because of: ( i ) form networks of mycelia and produce exopolysaccharides that aid in colonization of both materials [6,20], ( ii ) produce an ample gamut of extracellular enzymes such as ligninases (E.C. 1.11.1.14), cellulases (E.C.…”