Intraspecific variability of growth and ochratoxin A production by Aspergillus carbonarius from different foods and geographical areas

M.R Bragulat,M.L Abarca,G Castellá,F.J Cabañes

doi:10.1016/j.ijfoodmicro.2019.108273

M.R Bragulat, M.L Abarca + Show 2 more

Open Access

https://doi.org/10.1016/j.ijfoodmicro.2019.108273

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Abstract

Ochratoxin A (OTA) is a nephrotoxic mycotoxin naturally found in a wide range of food commodities throughout the world. Aspergillus carbonarius is the most important source of OTA in food commodities such as wine, grapes and dried vine fruits and is also responsible for the formation of OTA in coffee.The aim of this study was to determine the simultaneous effect of three culture media (Czapek Yeast Extract Broth (CYB); Synthetic Grape Juice Medium (SGM) and White grape juice (WGJ)) at three water activity (aw) levels (0.90; 0.95 and 0.98–0.99), and three incubation temperatures (15 °C, 25 °C and 35 °C) on the growth and OTA production by 16 strains of A. carbonarius. The strains were mainly isolated from grapes from areas with a Mediterranean climate. All the strains were confirmed for identity by sequencing of the calmodulin gene. The assay was performed in microtiter plates, determining the absorbance at 530 nm and the concentration of OTA after 1, 2, 4 and 10 days of incubation.No significant differences were observed in absorbance values between the strains. The highest absorbance values were recorded in CYB at 0.99 aw and at 0.95 aw after 10 days of incubation at 25 °C and 35 °C. None of the strains were able to grow at 0.90 aw and 15 °C in any culture media after 10 days of incubation. OTA concentration was statistically higher at 15 °C than at 25 °C or 35 °C. The highest significant OTA values were obtained at 0.98–0.99 aw and the best culture media for OTA production was CYB, followed by WGJ and SGM. While strains isolated from Mediterranean climate foods had a similar behavior despite being isolated from different geographical areas, OTA concentration produced by one Robusta coffee strain from Thailand was statistically higher at 25 °C than at 15 °C. This would suggest that the type of food matrices and consequently the adaptation of A. carbonarius strains to different climatic conditions would have a greater influence on the ecophysiology of the strains than only their geographical origin.

Highlights

Ochratoxin A (OTA) is a mycotoxin produced by several fungal species of the genera Penicillium and Aspergillus
Dried vine fruit and grape juice contributed to a significant extent to the OTA
Coffee represented the third contributor to the mean European total dietary intake of OTA (European Commission, 2002)

Summary

Introduction

Ochratoxin A (OTA) is a mycotoxin produced by several fungal species of the genera Penicillium and Aspergillus. OTA contamination of food commodities, including cereals and cereal products, pulses, coffee, beer, grape juice, dry vine fruits and wine as well as cacao products, nuts and spices, has been reported from all over the world (EFSA 2006). In the European diet, wine was identified as the second contributor to the human OTA exposure after cereals. Dried vine fruit and grape juice contributed to a significant extent to the OTA-. Coffee represented the third contributor to the mean European total dietary intake of OTA (European Commission, 2002). As a consequence of the possible health hazards related to ingestion of OTA, the European Union introduced maximum limits for OTA in a wide range of foodstuffs (Commission of the European Communities 2006; 2010; 2012; 2015)

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