Physiological behaviour of gliotoxigenicAspergillus fumigatus sensu strictoisolated from maize silage under simulated environmental conditions

Abstract

Environmental conditions play a key role in fungal development. During the silage production process, humidity, oxygen availability and pH vary among lactic-fermentation phases and among different silage sections. The aim of this work was to study the physiological behaviour of gliotoxicogenic Aspergillus fumigatus strains isolated from maize silage under simulated natural physicochemical conditions - different water activities (a(W)), temperatures (Tº), pH and oxygen pressure - on the growth parameters (growth rate and lag phase) and gliotoxin production. The silage was made with the harvested whole maize plant that was chopped and used for trench-type silo fabrication. Water activity and pH of the silage samples were determined. Total fungal counts were performed on Dichloran Rose Bengal Chloramphenicol agar and Dichloran 18% Glycerol agar. The morphological identification of A. fumigatus was performed with different culture media and at different growth temperature to observe microscopic and macroscopic characteristics. Gliotoxin production by A. fumigatus was determined by HPLC. All strains isolated were morphologically identified as A. fumigatus. Two A. fumigatus strains isolated from the silage samples were selected for the ecophysiological study (A. fumigatus sensu stricto RC031 and RC032). The results of this investigation showed that the fungus grows in the simulated natural physicochemical conditions of corn silage and produces gliotoxin. The study of the physiological behaviour of gliotoxigenic A. fumigatus under simulated environmental conditions allowed its behaviour to be predicted in silage and this will in future enable appropriate control strategies to be developed to prevent the spread of this fungus and toxin production that leads to impairment and reduced quality of silage.

Occurrence, prevention and remediation of toxigenic fungi and mycotoxins in silage: a review

“…Other fungal species well adapted to ensilage conditions are Monascus ruber and Byssochlamys nivea . Recently, Alonso et al have studied toxigenic A. fumigatus strains isolated from maize silage and their gliotoxin production in vitro under environmental conditions as occurring in silage (i.e. water activity, temperature, pH and oxygen pressure).…”

Modelling the effect of pH and water activity in the growth ofAspergillus fumigatusisolated from corn silage

“…; Alonso et al . , ). Mathematical modelling can be a useful tool to predict, and consequently to prevent, the growth of mycotoxicogenic fungi and also to study their response to environmental factors.…”

“…Besides, the prevention of fungal growth effectively prevents mycotoxin accumulation. Although some studies have determined the influence of environmental factors on the growth of A. fumigatus, none of them applied mathematical models to quantify these effects Alonso et al 2015Alonso et al , 2016. Mathematical modelling can be a useful tool to predict, and consequently to prevent, the growth of mycotoxicogenic fungi and also to study their response to environmental factors.…”

“…However, these models have not been, so far, applied to study the growth of A. fumigatus. In this work, the growth of the same A. fumigatus strains used by Alonso et al (2015) was assessed under a number of levels of factors (a W , pH). Therefore, the aim of this work was to use mathematical kinetic modelling to assess the combined effects of a W , pH, O 2 availability and temperature on the growth rate and time to growth of A. fumigatus strains isolated from corn silage.…”

Ecophysiology of environmental Aspergillus fumigatus and comparison with clinical strains on gliotoxin production and elastase activity

“…Other studies (Alonso et al . ) demonstrated that A. fumigatus strains were able to grow at 25°C even if the availability of oxygen was reduced at very low pH (4–5). However, no studies have been conducted with A. fumigatus strains from silages to which farm workers are exposed.…”