Effect of pH on the ultrastructure of Aspergillus niger aggregate wall dead conidia and its relation with zearalenone adsorption.

PEREYRA C.M., ; POLONI V,; CAVAGLIERI L.R.,; CRISTOFOLINI A, ; MERKIS C., ; PEREYRA C.M., ALONSO V.A, FERNÁNDEZ-JURI M.G., GONZALEZ-PEREYRA M.L., CHIACCHIERA S.M., ROSA C.A.R., DALCERO A.M., CAVAGLIERI L.R; DALCERO A.M.

World Mycotoxin Journal

Wagenigen academic publishers

Lugar: Amsterdam; Año: 2016 vol. 9 p. 389 - 395

1875-0710

The purpose of the present study was to evaluate the effect of pH on the ultra-structure of wall dead conidia harvested from non-toxicogenic Aspergillus niger aggregate and its relation with zearalenone adsorption capacity. Moreover, mathematical models to explain the interactions between adsorbent conidia and ZEA were applied. The adsorption test was performed using a concentration of 1 x 107 dead conidia/mL at pH 2 and pH 6 at 37ºC during 30 min. The extracts were quantified by high-pressure liquid chromatography. Isotherms representing the amount of bound ZEA as a function of the amount of ZEA in equilibrium after adsorption have typical S or L-shapes. The experimental data were fitted by mathematical expressions proposed by Frumkin-Fowler-Guggenheim (FFG) and Hill theoretical models. The ultrastructure of the wall of the conidia was shown by infrared spectroscopy (IR) and transmission electron microscopy (TEM). The ZEA adsorption was strongly dependent on the pH of the medium. The highest values were 2.2 x 10-6 µg ZEA/conidia at pH 6. The representative IR spectra showed that pH did not produce significant changes on the different chemical groups. However, ultrastructure studies by TEM detected considerable changes in the organization of the conidial wall. This is the first study showing that the loss of the outermost electron dense layer responsible for the ornamentations on the conidial surface at pH 6 potentiates the ZEA adsorption by IR spectroscopy and TEM methodologies. This is a novel tool to be applied in the adsorption of ZEA with importance in livestock production.