*Plastics Polymers Degradation by Fungi DOI: http://dx.doi.org/10.5772/intechopen.88608*

#### **Figure 7.**

*Microorganisms*

**Figure 5.**

**266**

**Figure 6.**

*P. ostreatus* PLO6.

*Scanning electron micrograph of oxo-biodegradable plastics after 60 days of exposure to sunlight and 30 days of* 

(**Figure 5B**) of exposure to sunlight and 30 days incubation with the fungus. The yellow circle and the red arrow show, respectively, the mycelial growth on the paper towel and plastic. This paper was added in the culture medium to retain moisture and to be an inducer of fungal growth and stimulates the synthesis of lignocellulo-

*Mycelial growth of* Pleurotus ostreatus *after 30 days of incubation in paper towel and oxo-biodegradable plastic bags after 30 (A) and 90 (B) days of exposure to sunlight. The arrow and circle show mycelial growth.*

The respiratory activity of *P. ostreatus* was influenced by time exposure to sunlight. This result confirms that the physical changes caused by sunlight contributed to the fungal growth in plastic bags. Furthermore, we did not observe reduction of this activity until 90 days of incubation showing a cellular activity for a long period. The activity of lignocellulolytic enzymes, like laccase, cellulase and xylanase, during 45 days of incubation of *P. ostreatus* in oxo-biodegradable plastics was observed [13]. The *P. ostreatus* growth on the surface of oxo-biodegradable plastic was also observed by SEM (**Figure 6**). 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. [13–15] 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

lytic enzymes that degrades the paper itself and the plastic (**Figure 5**).

*incubation with* Pleurotus ostreatus*. The arrows show the hyphae.*

*Loss of dry mass plastic after inoculated with* Pleurotus ostreatus *in oxo-biodegradable plastic bags before (0uv) or after 30, 60, 90 and 120 days of exposure to sunlight.*

#### **Figure 8.**

*Scanning electron micrograph of oxo-biodegradable plastics bags after 30 days of exposure to sunlight and 30 days of incubation with* Pleurotus ostreatus*. Micrograph without (A) and with a scale of 100 folds (B).*

The loss of plastic dry mass was influenced by the time of exposure to sunlight and fungal incubation (**Figure 7**). Fungal growth was lower in plastic polymers without exposure to sunlight than in others with different time of exposure to sunlight. This result shows that *P. ostreatus* can grow in plastic waste without or with exposure to sunlight. However, this exposure facilitates the fungal growth, as shown by Da Luz et al. [14, 15]. Thus, the combination of abiotic and biotic processes shows to be more efficient in the oxo-biodegradable plastic and green polyethylene degradation. In addition, the presence of other carbon sources from marine sediments and lack of abiotic degradation as the initiator were the main factors of the lack of biodegradation of polyethylene and biodegradable plastic bags after 100 days of incubation with benthic microbes [3].

In this study, we observed the formation of cracks and holes in oxo-biodegradable plastics and green polyethylene after fungal growth (**Figures 8** and **9**).

#### **Figure 9.**

*Scanning electron micrograph of green polyethylene plastics bags after 30 days of exposure to sunlight and 30 days of incubation with* Pleurotus ostreatus*. Micrograph without (A) and with scaling of 100 fold (B).*

Comparing the **Figure 2B** and **8** it is observed that these changes in plastic polymers were caused by *P. ostreatus* growth. The fungi, *Penicillium oxalicum*, *Penicillium chrysogenum*, *Myceliophthora* sp., *Phanerochaete chrysosporium*, and *Trametes versicolor*, also exhibit the ability to degrade polyethylene [16, 31, 32].

In a simulation according to ASTM G160–03 of polyethylene films degradation with and without pro-oxidant additive through the exposure to sunlight on the soil, different genera or microbial groups, *Geothrichum* spp., *Muco*r spp., *Rhizopus* spp., *Thichoderma* spp., *Penicillium* spp., *Aspergillus* spp. and Zygomycota, were identified [28]. These results indicate that (1) the plastic films did not alter or inhibit the development of the microbial community of the soil, since these microorganisms are part of the natural microbial community of the soil or (2) the growth of these microorganisms was due to the use of the films as source of carbon and energy. According to the authors, the biodegradation of polyethylene without or with pro-oxidant additive can be shown by the adhesion and surface erosion of the films, microbial colonization and presence of fruiting bodies and hyphae on the plastic surface.

The **Figures 8** and **9** show the plastic degradation with 30 days of exposure to sunlight and 30 days of incubation with different scale enlargements. 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. Furthermore, the LDPE after mycelia fungal may be used by biochar production [30].

The laccase produced by the fungus *Cochliobolu*s sp. isolated from plastic dumped soils showed capacity for polyvinyl chloride degradation [33]. This enzyme produced by *Myceliophthora* sp. was also able to degrade polyethylene [30] and polyurethane [34]. Manganese peroxidase from white rot fungi, *Phanerochaete chrysosporium*, is involved in the degradation of nylon and polyethylene [35]. The laccase and manganese peroxidase activity of *Penicillium* sp. are responsible by degradation of polyethylene [31, 36] and natural rubber [37]. These studies confirm the low specificity of these enzymes to the substrate.

After 120 days exposure to sunlight, no changes in the FTIR spectrum of oxo-biodegradable plastics was observed. This result shows that pro-oxidant oxidation by sunlight was not sufficient for cleavage of the polymer chain or it there is no oxidation thereof. However, in a previous study, a reduction of the relative

**269**

**Figure 10.**

*Plastics Polymers Degradation by Fungi DOI: http://dx.doi.org/10.5772/intechopen.88608*

at 3500–3000 cm<sup>−</sup><sup>1</sup>

polymers (13–15).

sunlight and fungal incubation.

concentration of titanium on the surface of oxo-biodegradable plastics wastes after exposure to sunlight was observed [14]. According to these authors, the oxidation of the pro-oxidant may have occurred initially by sunlight and then by co-metabolism with the extracellular fungal enzymes. The authors concluded that the presence of this pro-oxidant proved to be important to cause the breakage of this chain in frag-

In polyethylene green, which contain none pro-oxidant additive, no changes in

The formation of bands of the bonds oxygen-hydrogen and carbon-hydrogen

were the main changes in the FTIR spectra observed in plastic waste after *P. ostreatus* growth. The carbon-hydrogen bond band may be evidence of the fragmentation of the polyethylene chain. The other bands observed indicate that an oxidation has occurred, which may have contributed to the fungal colonization in the plastic

In studies on the plastics degradation for *P. ostreatus*, the authors also observed

The intensity of the degradation was higher in the green polyethylene than in the oxo-biodegradable polymers (**Figures 8** and **9**). The green polyethylene degradation by fungus was possible due to the presence of sugarcane polymers in the composition of the bags, low specificity of the lignocellulolytic enzymes and presence of endomycotic nitrogen-fixing microorganisms. In addition, Da Luz et al. [15] was observed mineralization in green polyethylene with longer times of exposure to

Similar to Da Luz et al. [13], during the time of incubation we also observed the mushrooms formation in the plastic (**Figure 10**). The conversion of plastic waste into fungal biomass and mushrooms would be a very important biotechnological innovation for plastic waste degradation that has been increased by millions of tons in recent years [1, 3, 16] and for environmental sustainability. However, the presence of toxic compounds and heavy metals, and also due to the low productivity and high costs are the main limitations to mushrooms production. Productivity in mushrooms can be increased by altering the composition of substrate, as for example, adding different proportions of agroindustrial residue and plastic.

chemical and physical changes similar to the observed in our study [29, 30].

*Mycelial growth and* Pleurotus ostreatus *mushrooms (arrows) formation in substrate containing* 

*oxo-biodegradable plastics and paper towels (99: 1 m/m).*

and carbon–oxygen and ether or peroxide at 1500–1000 cm<sup>−</sup><sup>1</sup>

ments that were used as a source of carbon and energy by fungus.

the FTIR spectrum after exposure to sunlight was observed.

#### *Plastics Polymers Degradation by Fungi DOI: http://dx.doi.org/10.5772/intechopen.88608*

*Microorganisms*

**Figure 9.**

Comparing the **Figure 2B** and **8** it is observed that these changes in plastic polymers were caused by *P. ostreatus* growth. The fungi, *Penicillium oxalicum*, *Penicillium chrysogenum*, *Myceliophthora* sp., *Phanerochaete chrysosporium*, and *Trametes versi-*

*Scanning electron micrograph of green polyethylene plastics bags after 30 days of exposure to sunlight and 30 days of incubation with* Pleurotus ostreatus*. Micrograph without (A) and with scaling of 100 fold (B).*

In a simulation according to ASTM G160–03 of polyethylene films degradation with and without pro-oxidant additive through the exposure to sunlight on the soil, different genera or microbial groups, *Geothrichum* spp., *Muco*r spp., *Rhizopus* spp., *Thichoderma* spp., *Penicillium* spp., *Aspergillus* spp. and Zygomycota, were identified [28]. These results indicate that (1) the plastic films did not alter or inhibit the development of the microbial community of the soil, since these microorganisms are part of the natural microbial community of the soil or (2) the growth of these microorganisms was due to the use of the films as source of carbon and energy. According to the authors, the biodegradation of polyethylene without or with pro-oxidant additive can be shown by the adhesion and surface erosion of the films, microbial colonization and presence of fruiting bodies and hyphae on the plastic surface. The **Figures 8** and **9** show the plastic degradation with 30 days of exposure to sunlight and 30 days of incubation with different scale enlargements. 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. Furthermore, the LDPE after mycelia

The laccase produced by the fungus *Cochliobolu*s sp. isolated from plastic dumped soils showed capacity for polyvinyl chloride degradation [33]. This enzyme produced by *Myceliophthora* sp. was also able to degrade polyethylene [30] and polyurethane [34]. Manganese peroxidase from white rot fungi, *Phanerochaete chrysosporium*, is involved in the degradation of nylon and polyethylene [35]. The laccase and manganese peroxidase activity of *Penicillium* sp. are responsible by degradation of polyethylene [31, 36] and natural rubber [37]. These studies confirm

After 120 days exposure to sunlight, no changes in the FTIR spectrum of oxo-biodegradable plastics was observed. This result shows that pro-oxidant

oxidation by sunlight was not sufficient for cleavage of the polymer chain or it there is no oxidation thereof. However, in a previous study, a reduction of the relative

*color*, also exhibit the ability to degrade polyethylene [16, 31, 32].

fungal may be used by biochar production [30].

the low specificity of these enzymes to the substrate.

**268**

concentration of titanium on the surface of oxo-biodegradable plastics wastes after exposure to sunlight was observed [14]. According to these authors, the oxidation of the pro-oxidant may have occurred initially by sunlight and then by co-metabolism with the extracellular fungal enzymes. The authors concluded that the presence of this pro-oxidant proved to be important to cause the breakage of this chain in fragments that were used as a source of carbon and energy by fungus.

In polyethylene green, which contain none pro-oxidant additive, no changes in the FTIR spectrum after exposure to sunlight was observed.

The formation of bands of the bonds oxygen-hydrogen and carbon-hydrogen at 3500–3000 cm<sup>−</sup><sup>1</sup> and carbon–oxygen and ether or peroxide at 1500–1000 cm<sup>−</sup><sup>1</sup> were the main changes in the FTIR spectra observed in plastic waste after *P. ostreatus* growth. The carbon-hydrogen bond band may be evidence of the fragmentation of the polyethylene chain. The other bands observed indicate that an oxidation has occurred, which may have contributed to the fungal colonization in the plastic polymers (13–15).

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].

The intensity of the degradation was higher in the green polyethylene than in the oxo-biodegradable polymers (**Figures 8** and **9**). The green polyethylene degradation by fungus was possible due to the presence of sugarcane polymers in the composition of the bags, low specificity of the lignocellulolytic enzymes and presence of endomycotic nitrogen-fixing microorganisms. In addition, Da Luz et al. [15] was observed mineralization in green polyethylene with longer times of exposure to sunlight and fungal incubation.

Similar to Da Luz et al. [13], during the time of incubation we also observed the mushrooms formation in the plastic (**Figure 10**). The conversion of plastic waste into fungal biomass and mushrooms would be a very important biotechnological innovation for plastic waste degradation that has been increased by millions of tons in recent years [1, 3, 16] and for environmental sustainability. However, the presence of toxic compounds and heavy metals, and also due to the low productivity and high costs are the main limitations to mushrooms production. Productivity in mushrooms can be increased by altering the composition of substrate, as for example, adding different proportions of agroindustrial residue and plastic.

#### **Figure 10.**

*Mycelial growth and* Pleurotus ostreatus *mushrooms (arrows) formation in substrate containing oxo-biodegradable plastics and paper towels (99: 1 m/m).*
