Investigation and Biological Control of Toxigenic Fungi and Mycotoxins in Dairy Cattle Feed

Abstract

Mycotoxins are secondary metabolites synthesized by mycotoxigenic fungi, contaminating human and animal food and feed. Aflatoxin B1 (AFB1) and ochratoxins (OTA) are frequently detected in animal feed products causing many health issues in humans and animals. In this M. Sc research work, we evidenced the presence of OTA and AFs below the EU maximum permissible limits. Mycotoxigenic fungal strains have been isolated from the animal feeds. The morphological and molecular identification of these toxigenic fungi allowed the evidence of A. flavus, A. niger, A. carbonarius and P. verrucosum that synthesize during their growth mycotoxins compounds (Aflatoxins & Ochratoxins) at levels higher than the detection limits and the corresponding genes were evidenced. In order to set up safe and efficient biological control strategy of these mycotoxigenic fungi, we decided to use yeasts known to be very safe for such purpose. Thus, in the second part of this Thesis, 14 yeast strains were isolated from different fermented food, dairy and meat products. These strains showed a great antifungal and spectrum of activities through the synthesis of Volatile Organic Compounds (VOCs). Among these yeast strains, a particular strain of Kluyveromyces marxianus QKM-4, had the strongest antifungal VOCs that we were able to identify. GC/MS based analysis of yeast VOCs showed long chain alkanes including nonadecane (C19), eicosane (C20), docosane (C22), heptacosane (C27), hexatriacontane (C36) and tetracosane (C24) that can control the mycotoxigenic fungal strains and their mycotoxins synthesis. Testing the mycotoxin binding potential of the live and heat-inactivated QKM-4 cells, showed the reduction of OTA and DON up to 58% and 49%. The findings of the present study clearly demonstrate a strong antifungal potential of Kluyveromyces marxianus QKM-4 for its possible application in the agriculture and food industry. In another applied part of the present work, the strain QKM-4 of Kluyveromyces marxianus showed a great inhibition potential of the mycotoxigenic fungal growth, spore’s germination and 100% protection of tomato and grape fruits from the in vitro infection of the latter by mycotoxigenic fungi for more than 10 days.