• Fungi degrade reduced graphene oxide (rGO), polyamide 6 (PA6) and the PA6-rGO complex • Fungal degradation increases in nutrient-depleted media and co-cultures • Hydrolytic by-products of PA6 affect Laccase and Lignin Peroxidase activity • Morel exudates degrade PA6 more efficiently than those of a white rot fungus • rGO added to PA6 is not degraded but it does not reduce PA6 degradation The large-scale production, marketing and disposal of polymer-based graphene products can lead to the dispersal of graphene-enriched plastic particles into terrestrial ecosystems, where they might accumulate if not degraded by organisms. The objective of this work is to test the degradability and compatibility of one polyamide-6 polymer reinforced with reduced graphene-oxide (PA6-rGO) and its base constituents (polyamide-6, PA6; reduced graphene oxide, rGO) using mono- and co-cultures of two lignin-degrading fungi ( Bjerkandera adusta and Morchella esculenta ) grown under different nutrient conditions. Fungal (co-)cultures were exposed to pure rGO or abraded powders of PA6 and PA6-rGO in two different liquid media, and monitored over time for biomass growth, H 2 O 2 production, and activity of two lignolytic enzymes (i.e, Laccase, Lac, and Lignin peroxidase, LiP). The changes in polyamide structure were evaluated by proton nuclear magnetic resonance and mass spectrometry, and changes in rGO were evaluated by Raman spectroscopy. The materials had no effect on fungal growth. PA6 increased Lac secretion only in low nutrient medium, while PA6-rGO slightly suppressed LiP activity. Only M. esculenta promoted polyamides oxidation when cultured in a low nutrient medium, as evidenced by a change in mass distribution values ( m / z : 400-420) and the appearance of a new resonance peak (at 5.37 ppm). Lignolytic exudates in co-cultures low in nutrients caused a greater change in rGO, as shown by the increase in the I D / I G ratio. The degradation of rGO, PA6 and PA6-rGO depended on culture conditions.
Fortuna et al. (Wed,) studied this question.