Effect of pH on the ultrastructure of the conidial wall of Aspergillus niger aggregate conidia and its relationship to zearalenone adsorption

PEREYRA, C.M; CAVAGLIERI, L.R; POLONI, V.L; CHIACCHIERA, S.M; CRISTOFOLINI, A; MERKIS, C; DALCERO A.M

World Mycotoxin Journal

Wageningen Academic P u b l i s h e r s

Lugar: Londres; Año: 2016

1875-0710

The purpose of the present study was to evaluate the effect of pH on the ultrastructure of the conidial wall of deadconidia harvested from the non-toxicogenic Aspergillus niger aggregate strain RC084 and its relationship to zearalenone(ZEA) adsorption capacity. Moreover, mathematical models were applied to explain the interaction between conidiaand ZEA absorbance. A ZEA adsorption test was performed using a concentration of 1×107 dead conidia/ml atpH 2 and 6 at 37 °C for 30 min. Unbound ZEA was quantified by high-pressure liquid chromatography. The ZEAadsorption was strongly dependent on the pH of the medium; the highest values were 2.2×10-6 μg ZEA/conidia atpH 6. Isotherms representing the amount of bound ZEA as a function of ZEA concentration in equilibrium afteradsorption have typical S- or L-shapes. The experimental data could be fitted to the Frumkin-Fowler-Guggenheim(FFG) and Hill theoretical models. The ultrastructure of the conidial wall was studied by infrared spectroscopy(IR) and transmission electron microscopy (TEM). The representative IR spectra showed that pH did not producesignificant changes in the different chemical groups. However, ultrastructure studies by TEM detected considerablechanges in the organisation of the conidial wall. This is the first study showing that the loss of the outermost electrondense layer, responsible for the ornamentations on the conidial surface, at pH 6 potentiates ZEA adsorption.