Souheib Oueslati

Multi-mycotoxin determination in cereals and derived products marketed in Tunisia using ultra-high performance liquid chromatography coupled to triple quadrupole mass spectrometry.

The aim of the study was the use of a fast and simple method using ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS) for the simultaneous determination of aflatoxins (AFB1, AFB2, AFG1 and AFG2), ochratoxin A (OTA), fumonisins (FB1 and FB2), deoxynivalenol (DON), T2 and HT2 toxins in 58 samples of raw wheat (n = 34), barley (n = 5), sorghum (n = 3), processed wheat (n = 13) and breakfast cereals (n = 3) from Tunisian markets. The frequency of contamination of total samples with the analyzed mycotoxins was 50%. AFG2 was the most frequently detected in 11 samples (4 wheat, 4 barley and 3 sorghum) and it was detected at 5.2-52.4 μg/kg. HT2 toxin contaminated seven samples (4 wheat and 3 barley) and it was detected at 5.0-11.1 μg/kg. FB2 was detected in one wheat, sorghum, semolina and breakfast cereal samples at 5.0-61.5 μg/kg. FB1 was detected in three samples (2 sorghum and one barley) at 6.4-120 μg/kg. AFB1 was only found in two sorghum samples at 14 and 79.9 μg/kg. OTA was detected in one sorghum sample at concentrations below limit of quantification (5 μg/kg). The analytical results also showed that all the analyzed samples were not contaminated with DON, AFG1, AFB2 and T2 toxin.

Water Activity and Temperature Effects on Fungal Growth and Ochratoxin A Production by Ochratoxigenic Aspergillus carbonarius Isolated from Tunisian Grapes

This study investigated the effects of temperature (15 to 37 degrees C) and water activity (0.90 to 0.99) on the growth and production of ochratoxin A (OTA) by Aspergillus carbonarius cultured on synthetic nutrient medium (SNM) after 5 and 10 d of incubation. Total of 8 ochratoxigenic A. carbonarius, isolated from vineyards located in different regions of Tunisia, were used. Growth data were modeled by the flexible model of Baranyi and growth rates at each set of conditions were obtained. For both growth and OTA production, optimal water activity was 0.99; however, optimal temperature varied. The optimal temperature for growth was 30 degrees C. At 37 degrees C, the growth rate decreased significantly (P < 0.05). Maximum toxin production occurred at temperatures in the range of 15 to 25 degrees C with the optimum one depending on the isolate tested. Significant amounts of OTA were produced after only 5 d of incubation. Our results showed that A. carbonarius isolated from Tunisian grapes behave as those from European and Australian grapes, as reported in the literature, although some differences in trends for growth and OTA production were observed.

Presence of mycotoxins in sorghum and intake estimation in Tunisia

Sorghum samples (n = 60) from Tunisian markets were analysed for the occurrence of 22 of both traditional and emerging mycotoxins. Samples were extracted with a QuEChERS-like method and mycotoxins were detected by LC-MS/MS. This method was validated and adequate analytical parameters were obtained. All samples had contamination with mycotoxins and several samples had higher contamination levels than European Union legislative limits (MLs). The most frequently found mycotoxins were ENB (100%), OTA (98%), ENA1 (63%), ENB1 (56%), BEA (48%), AFB1 (38%) and STG (33%). Mean contaminations were 30.7, 1.93, 33.2, 51.0, 15.4, 1.49 and 20.5 µg kg–1, respectively. While two samples were contaminated with FB2 and FB3 at mean values of 16.2 and 45.9 µg kg–1, respectively, one sample was contaminated with AFB2 and ZEA at levels of 0.82 and 45.0 µg kg–1, respectively. The results were used to estimate the daily intake of mycotoxins through sorghum consumption with regard to normal consumers (low-risk population) and high consumers such as babies (high-risk consumers) who are facing an alarming situation.

Alternating temperatures and photoperiod effects on fungal growth and Ochratoxin A production by Aspergillus carbonarius isolated from Tunisian grapes

The effect of three alternating temperatures cycles (20/30, 20/37 and 25/42 degrees C) and photoperiod on growth and Ochratoxin A (OTA) production of six isolates of Aspergillus carbonarius on synthetic nutrient medium were investigated. The different temperature regimes affected significantly both the mycelial growth and the OTA production. The best growth and OTA production were recorded at 20/30 degrees C. The isolates from the region of Baddar produced the highest OTA yields. A 24 h light cycle generally enhanced the growth of A. carbonarius. Growth rates cycles of 11 h/13 h light/darkness and 24 h darkness were often similar for individual isolates, such conditions enhanced OTA production in two of the six isolates tested.

Evaluation of Alternaria mycotoxins in strawberries: quantification and storage condition

ABSTRACT Alternariol (AOH), alternariol methyl ether (AME) and tentoxin (TEN) are Alternaria mycotoxins produced by the most common post-harvest pathogens of fruits. The production of these metabolites depends on several environmental factors, mainly temperature, water activity, pH and the technological treatments that have been applied to the product. In this study, the occurrence of AOH, AME and TEN was evaluated in strawberries samples stored at different temperatures ranges (at 22 ± 2 or 6 ± 2°C) and different periods (up to 1 month) simulating the current practice of consumer’s storage conditions. Sample extraction was performed using a liquid–liquid extraction method prior to LC-MS/MS analysis. AOH was the most prevalent mycotoxins with a 42% at strawberries stored at (22 ± 2)°C and 37% stored at (6 ± 2)°C. The highest AOH levels were found in samples conserved at (22 ± 2)°C ranging between 26 and 752 ng g–1. AME levels ranged between 11 and 137 ng g–1, which were found mainly in stored samples at (6 ± 2)°C for more than 28 days. None sample presented levels of TEN in either of the studied conditions.

Universal direct PCR amplification system: a time- and cost-effective tool for high-throughput applications

Taking into account the limits of current genotyping methodologies, we have established a versatile direct PCR method on intact microtissue samples without prior DNA isolation. A simple and standard protocol was developed and validated on a wide range of living organisms including bacterial and fungal strains, plant species and human samples. This allows reliable amplification of target genomic DNA fragment directly from source material using minimal amount of tissue which makes DNA purification irrelevant for a number of biological applications. The direct PCR technique established here represents an excellent alternative to traditional amplification methods used for real-time detection. Since this approach was efficiently and universally applied for high-throughput molecular screening, its implementation will offer new insights for several investigations in human health, biomedical diagnosis, plant biotechnology, as well as in applied environmental and food microbiology.