Sorghum, which is consumed in Tunisia as human food, suffers from severe colonization by several toxigenic fungi and contamination by mycotoxins. The Tunisian climate is characterized by high temperature and humidity that stimulates mold proliferation and mycotoxin accumulation in foodstuffs. This study investigated the effects of temperature (15, 25 and 37°C), water activity (aw, between 0.85 and 0.99) and incubation time (7, 14, 21 and 28 d) on fungal growth and aflatoxin B1 (AFB1) production by three Aspergillus flavus isolates (8, 10 and 14) inoculated on sorghum grains. The Baranyi model was applied to identify the limits of growth and mycotoxin production. Maximum diameter growth rates were observed at 0.99 a(w) at 37°C for two of the isolates. The minimum aw needed for mycelial growth was 0.91 at 25 and 37°C. At 15°C, only isolate 8 grew at 0.99 a(w). Aflatoxin B1 accumulation could be avoided by storing sorghum at low water activity levels (≤0.91 a(w)). Aflatoxin production was not observed at 15°C. This is the first work on the effects of water activity and temperature on A. flavus growth and AFB1 production by A. flavus isolates on sorghum grains.
Wheat, barley and maize are the mainly consumed cereals in Tunisia. This study aimed to determine the mycoflora of these cereals with special focus on the mycotoxigenic and species. Freshly harvested samples and other stored samples of each type of cereal (31 and 34 samples, respectively) were collected in Tunisia and cultured for fungal isolation and identification. Identification of fungal genera was based on morphological and species were identified by species specific PCR assays complemented with DNA sequencing. (70.83%), (62.50%), (54.17%) and (41.67%) were the most frequent fungi isolated from wheat. (75%), (70%), (65%) and (65%) were the most frequently recovered genera from barley. The predominant genera in maize were (76.19%), (42.86%), and (38.09%)., , and were detected in both stored and freshly harvested grain samples. The frequencies of contamination with, and were higher in freshly harvested samples, whereas species were more frequent in stored samples. The predominant species detected were and. The species detected were, ,, and . This study suggested the potential risk for Aflatoxins and, to a lesser extent, for Ochratoxin A in Tunisian cereals. This is the first survey about mycoflora associated with wheat, barley and maize in Tunisia.
a b s t r a c tThe objective of this study was to characterize the mycoflora of sorghum grains commercialized in the Tunisian retail market and to identify aflatoxins (AFs), ochratoxin A (OTA) and zearalenone (ZEA) producing species. Sixty four samples of sorghum (37 samples of Tunisian sorghum and 27 samples of Egyptian sorghum) were analyzed. Dilution plating (CFU, colony forming units) was used for fungal enumeration. The isolation of mycobiota was carried out by plating of grains on PDA and malachite green medium. Aspergillus section Flavi and section Nigri and Fusarium isolates were sub-cultured in CYA to test their ability to produce AFs, OTA and ZEA, respectively. The selected Aspergillus section Flavi and section Nigri, Penicillium and Fusarium isolates were subjected to specific PCR assays using published speciesspecific primers. The results revealed the dominance of Fusarium (95.3%), followed by Aspergillus (87.2%) and Alternaria (81.2%) species. The fungal counts ranged from 100 to 1.3$10 4 CFU/g for Tunisian sorghum and from 100 to 5.7$10 3 CFU/g for Egyptian sorghum. Among Aspergillus section Flavi isolates identified by molecular biology, Aspergillus flavus was the most dominant (90.1%) while Aspergillus parasiticus represent 9.9% only. About Aspergillus section Nigri, results showed the dominance of Aspergillus niger aggregate species, including Aspergillus niger, Aspergillus tubingensis and other species. Among Fusarium species, Fusarium incarnatum was the most dominant in both Tunisian and Egyptian sorghum. Penicillium citrinum was the dominant Penicillium species in the studied samples. More than 890 isolates belonging to the genus Aspergillus and Fusarium were tested in order to test their capacity to produce AFs, OTA and ZEA. The percentage of mycotoxin producing isolates in Aspergillus section Flavi, A. section Nigri, and Fusarium was 30.0%, 4.6% and 11.1%, respectively.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.