Fullerol C60(OH)24 nanoparticles modulate aflatoxin B1 biosynthesis in Aspergillus flavus

Tihomir Kovač,Michael Sulyok,Ivica Strelec,Bojan Šarkanj,Chibundu N Ezekiel,Frane Čačić Kenjerić,Marija Kovač,Ivana Borišev,Rudolf Krska,Biljana Crevar

doi:10.1038/s41598-018-31305-9

Abstract

The water soluble fullerene C60 daughter product - fullerols C60(OH)24 (FNP) possesses a great potential of modifying secondary metabolites biosynthesis. In order to clarify the extent of interaction, the impact of FNP (10, 100 and 1000 ng mL−1) on aflatoxin production and the available precursors of biosynthesis pathway from Aspergillus flavus NRRL 3251 was determined, in both the mycelia and yeast extract sucrose (YES) medium, during a 168-hour growth period at 29 °C in the dark. The FNP of 8 nm in diameter, and with a zeta potential of −33 mV affected mycelial growth at 1000 ng mL−1 while conidia production was slightly affected at 10 ng mL−1. The FNP effect on aflatoxin and it biosynthetic precursors was concentration dependent and alteration of the sterigmatocystin (ST) export from the cell was observed. Most of the monitored aflatoxin precursors, except norsolorinic acid, were detected in both mycelia and YES medium. However, observed precursor concentrations were much higher in mycelia, with exception of ST. The study shows the loss of FNP antioxidative effect after 120 hours of growth, and strong concentration dependent aflatoxigenic effect after that time. Thus, this data is relevant to guide future considerations on FNP-fungal interactions in the environments and on risk assessment.

Highlights

Fullerols C60(OH)[24] (FNP) are water soluble fullerene C60 daughter products with poorly defined environmental reactivity, distinctive material properties, and biological activities, which have gained great attention today
The 8 nm FNP agglomerates effect on A. flavus NRRL 3251 growth and secondary metabolism may have been due to interactions with and/or adsorption onto the fungal cell wall as proposed by Chen et al.[18] and Quiao et al.[19], as well as due to cell oxidative status modulation as established by Kovač et al.[13]
This study has shown that FNP modulates aflatoxin production by affecting the biosynthetic pathway of metabolites reported

Summary

Introduction

Fullerols C60(OH)[24] (FNP) are water soluble fullerene C60 daughter products with poorly defined environmental reactivity, distinctive material properties, and biological activities, which have gained great attention today. Milic Torres et al.[3] reported the antiproliferative properties and protective effects of fullerol against doxorubicin cytotoxicity mediated by antioxidative and hydroxyl radical scavenging activity. Grebowski et al.[4] reported that fullerol C60(OH)[36] protects human erythrocyte membrane against high-energy electrons due to their reactive oxidative species (ROS) scavenging ability. FNPs are mineralised in soils where the most important mycotoxin-producing saprophytic soil fungus, Aspergillus flavus, resides. These fungi are involved in pre-harvest and post-harvest crop colonization and contamination with aflatoxins. In a bid to resolve the cause and consequences of such interaction, the impact of FNP on aflatoxin biosynthesis precursors, in both the mycelia and growth medium were determined

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Conclusion