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Comparative Study
. 2021 Mar 28;22(7):3491.
doi: 10.3390/ijms22073491.

Comparative Study of Structural Changes of Polylactide and Poly(ethylene terephthalate) in the Presence of Trichoderma viride

Grażyna B Dąbrowska  1 , Zuzanna Garstecka  1 , Ewa Olewnik-Kruszkowska  2 , Grażyna Szczepańska  3 , Maciej Ostrowski  4 , Agnieszka Mierek-Adamska  1
Affiliations
Comparative Study

Comparative Study of Structural Changes of Polylactide and Poly(ethylene terephthalate) in the Presence of Trichoderma viride

Grażyna B Dąbrowska et al. Int J Mol Sci. .

Abstract

Plastic pollution is one of the crucial global challenges nowadays, and biodegradation is a promising approach to manage plastic waste in an environment-friendly and cost-effective way. In this study we identified the strain of fungus Trichoderma viride GZ1, which was characterized by particularly high pectinolytic activity. Using differential scanning calorimetry, Fourier-transform infrared spectroscopy techniques, and viscosity measurements we showed that three-month incubation of polylactide and polyethylene terephthalate in the presence of the fungus lead to significant changes of the surface of polylactide. Further, to gain insight into molecular mechanisms underneath the biodegradation process, western blot hybridization was used to show that in the presence of poly(ethylene terephthalate) (PET) in laboratory conditions the fungus produced hydrophobin proteins. The mycelium adhered to the plastic surface, which was confirmed by scanning electron microscopy, possibly due to the presence of hydrophobins. Further, using atomic force microscopy we demonstrated for the first time the formation of hydrophobin film on the surface of aliphatic polylactide (PLA) and PET by T. viride GZ1. This is the first stage of research that will be continued under environmental conditions, potentially leading to a practical application.

Keywords: Trichoderma viride; bioremediation; hydrophobin; hydrophobin film; poly(ethylene terephthalate); polylactide.

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Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

Figures

Figure 1
Figure 1
SEM analysis (magnification 10,000×) of the polymer materials after 3-month incubation in liquid medium: the left-hand side shows polymers incubated without fungus (control), and the right-hand side shows polymers incubated with T. viride GZ1. Red circles indicate spots where the release of the cytoplasmic content of hyphae takes place.
Figure 2
Figure 2
Differential scanning calorimetry (DSC) thermograms of (a) aliphatic polylactide (PLA) and (b) poly(ethylene terephthalate) (PET), before treatment (PLA/PET), after 3-month incubation in clean medium (PLA/PET−medium), and after 3-month incubation in medium containing T. viride GZ1 (PLA/PET−T. viride).
Figure 3
Figure 3
Infrared spectra of (a) PLA, and (b) PET, before treatment (red line), after 3-month incubation in medium (black line), and after 3-month incubation in medium-T. viride GZ1 (green line).
Figure 4
Figure 4
Reduced viscosity ηsp/c versus (a) PLA and (b) PET concentration, before and after the incubation of the polymer in medium (PLA/PET−medium) or in fungal culture (PLA/PET−T. viride).
Figure 5
Figure 5
Western blot analysis of hydrophobin. Proteins were immunoprecipitated using anti-HFBI antibody, and resulting pellets were washed and subjected to SDS-PAGE/Western blot analysis. Lane 1: liquid medium, lane 2: T. viride GZ1 culture, lane 3: liquid medium with PET, lane 4: T. viride GZ1 culture with PET, and M: molecular mass standard (BluEasy Prestained Protein Marker, Nippon Genetics, Dürren, Germany). All analyzed media/cultures were incubated for 3 months. Arrows indicate IgG heavy (52 kDa) and light (25 kDa) chains and protein that corresponds to HFBI (17 kDa).
Figure 6
Figure 6
Atomic force microscopy (AFM) images of PET (left-hand side) and PLA (right-hand side) before treatment, after 3-month incubation in medium, and after 3-month incubation in medium-T. viride GZ1.
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