Global Advanced Research Journal of Agricultural Science (GARJAS) ISSN: 2315-5094
October 2017 Vol. 6(10): pp. 314-322
Copyright © 2017 Global Advanced Research Journals

Full Length Research Paper

Growth and ochratoxin a production by Aspergillus carbonarius and Aspergillus niger in relation to culture medium, water activity and temperature

Souad Zouhair^*, Adil Laaziz, Souad Qjidaa and Amina Bouseta

Laboratoire d’agroalimentaire et sécurité sanitaire des aliments, Faculté des sciences Dhar El Mehraz, Université Sidi Mohamed Ben Abdellah, Fès, Maroc

Email: souad_zouhair@hotmail.com

Accepted 10 October, 2017

Abstract

The effect of culture medium (YES, CYA, SNM), temperature (10, 20, 25, 30 and 37°C), water activity (0.90, 0.95 and 0.99a_w), incubation time (5, 10, 15 and 20 days) and their interactions on the fungal growth and ochratoxin A production by two strains (A. niger and A. carbonarius) was studied. A total inhibition of the growth was observed at 10°C, whatever the culture medium and the water activity. Generally, the increase of the temperature increases the radial growth rate. The growth was favored on the YES and CYA media in all temperatures tested for A. niger with a maximal growth rate at 30°C (9.91 and 10.22 mm/day, respectively) while for A. carbonarius, the maximal growth was observed at 37°C on YES (6.03 mm/day). The decrease of the water activity on the SNM medium favors the growth of A. niger with a maximum in 0.90a_w /30°C. However, the radial growth rate of A. carbonarius was faster at 0.99a_w/37°C and at 0.95a_w/25°C. The biosynthesis of the OTA is favored by a temperature of 25°C on the SNM medium for A. carbonarius and on the YES medium for A. niger. Maximal levels were produced on the SNM medium by A. niger (3.0 ng/g) at 0.90a_w  and by A. carbonarius (704.8 ng/g) in a high water activity of 0.99a_w.

Keywords:  Aspergillus; fungal growth; ochratoxin A (OTA); culture medium; temperature; water activity.