Low toxicity of fluorescent carbon quantum dots to white rot fungus Phanerochaete chrysosporium

Abstract Carbon quantum dots (CQDs) are novel fluorescent nanomaterials for applications in diverse areas. With the rapid developments in past decade, the toxicity and environmental safety of CQDs have aroused great interest. In this study, we evaluated the toxicity and impact of CQDs to white rot fungus Phanerochaete chrysosporium, an important fungus for carbon cycle that degrades lignin. Red emissive CQDs slightly stimulated the growth of P. chrysosporium at 50 and 100 μg/mL. CQD aggregates heterogeneously distributed in fungus balls, where the tightly contacted mycelia lost their fibrous structure. Cell wall damage and the detachment of membrane were observed in ultrastructural investigations. CQDs did not affect the laccase and manganese peroxidase activities of P. chrysosporium. The decomposition activity of P. chrysosporium kept unchanged by CQDs according to dye decoloration, sawdust weight loss, and sawdust lignin content. CQDs initiated the protective pathways of P. chrysosporium against oxidative stress, leading to the increases of glutathione and catalase levels and the decreases of malondialdehyde and H2O2 levels. The fluorescence quenching of CQDs in P. chrysosporium implied the biotransformation of CQDs during the one-month incubation. Our results collectively suggested that CQDs were of low toxicity and environmental impacts to white rot fungi.