Molecular Characterization of Ochratoxigenic Fungi Associated with Raisins

Recent Advances in Mycotoxin Analysis and Detection of Mycotoxigenic Fungi in Grapes and Derived Products

Mycotoxins are secondary metabolites of filamentous fungi that can cause toxic effects in human and animal health. Most of the filamentous fungi that produce these mycotoxins belong to four genera, namely, Aspergillus, Penicillium, Fusarium, and Alternaria. Mycotoxigenic fungi, along with mycotoxins, create a constant and serious economic threat for agriculture in many terms, counting product losses due to crop contamination and food spoilage, as well malnutrition when considering nutritional quality degradation. Given the importance of robust and precise diagnostics of mycotoxins and the related producing fungi in the grape food chain, one of the most important agricultural sectors worldwide, the present review initially delivers a comprehensive presentation of mycotoxin reports on grape and derived products, including a wide range of commodities such as fresh grapes, raisins, wine, juices, and other processed products. Next, based on worldwide regulations’ requirements for mycotoxins, and referring to the relative literature, this work presents methodological approaches for mycotoxin determination, and stresses major methods for the detection of fungal species responsible for mycotoxin production. The principle of function and basic technical background on the available analytical and molecular biology techniques developed—including chromatography, mass spectrometry, immunochemical-based assays, biosensors, and molecular assays—is briefly given, and references for their application to grape and derived product testing are highlighted.

Molecular characterization of ochratoxigenic fungi associated with poultry feedstuffs in Saudi Arabia

Fungal and mycotoxins contamination of food and poultry feeds can occur at each step along the chain from grain production, storage, and processing. A total of 200 samples comprising of mixed poultry feedstuffs (n = 100) and their ingredients (n = 100) were collected from Riyadh, Alhassa, Qassium, and Jeddah cities in Saudi Arabia. These samples were screened for contamination by fungi. Penicillium chrysogenum was the predominant species taking into its account and frequency, respectively, in both mixed poultry feedstuff and barley samples (4,561.9 and 687 fungal colony-forming units (CFU)/g) and (66% and 17%). Moisture content was an important indicator for the count of fungi and ochratoxin A. Ochratoxin analysis of plate cultures was performed by a HPLC technique. Sample of mixed poultry feedstuff which was collected from Jeddah displayed the highest level of ochratoxin (14.8 µg/kg) and moisture content (11.5%). Corn grains samples were highly contaminated by ochratoxin A (450 and 423 µg/kg) and recorded the highest moisture contents (14.1 and 14.5%). Ochratoxin A production in fungal species isolated from mixed poultry feedstuff samples were high with P. verrucosum (5.5 μg/kg) and A. niger (1.1 μg/kg). In sorghum and corn grains, the highest ochratoxins producing species were P. viridicatum (5.9 μg/kg) and A. niger (1.3 μg/kg), respectively. Sixty-three isolates of A. niger were ochratoxigenic, and all of them showed the presence of pks genes using PKS15C-MeT and PKS15KS primer pairs. The detection technique of A. niger in poultry feedstuff samples described in the present study was successfully used as a rapid and specific protocol for early detection of A. niger without cultivation on specific media.

Genetic Diversity, Ochratoxin A and Fumonisin Profiles of Strains of Aspergillus Section Nigri Isolated from Dried Vine Fruits

We investigated ochratoxin A (OTA) contamination in raisin samples purchased from Slovak markets and determined the diversity of black-spored aspergilli as potential OTA and fumonisin (FB1 and FB2) producers. The taxonomic identification was performed using sequences of the nuclear ITS1-5.8s-ITS2 region, the calmodulin and beta-tubulin genes. We obtained 239 isolates from eight fungal genera, of which 197 belonged to Aspergillus (82%) and 42 strains (18%) to other fungal genera. OTA contamination was evidenced in 75% of the samples and its level ranged from 0.8 to 10.6 µg/kg. The combination of all three markers used enabled unambiguous identification of A. carbonarius, A. luchuensis, A. niger, A. tubingensis and A. welwitschiae. The dominant coloniser, simultaneously having the highest within-species diversity isolated from our raisin samples, was A. tubingensis. Out of all analysed strains, only A. carbonarius was found to produce OTA, but in relatively high quantity (2477–4382 µg/kg). The production of FB1 and FB2 was evidenced in A. niger strains only.

Effects of different drying treatments on fungal population and ochratoxin A occurrence in sultana type grapes

This study aimed to determine the changes in mould and ochratoxin A (OTA) occurrence in sultanas under three different conventional drying conditions. Five different vineyards were chosen, and the three different treatments were applied to these grapes while drying. At the end of the drying process, total mould and black aspergilli (BA) populations in the samples varied from 2.45 to 5.61 log colony-forming units (CFU) g(-)(1) and from 0 to 4.92 log CFU g(-)(1), respectively. Significant increases (p < 0.05) occurred in mould loads depending on the extending drying period. However, independent of vineyard location, all the samples treated with cold dipping solution showed the lowest fungal loads. These results indicate that dipping solution treatment was the most effective drying method to minimise fungal infection of grapes. The expected results could not be achieved by drying grapes artificially contaminated with ochratoxigenic Aspergillus carbonarius spores. Seventy-one of 96 isolates (73.95%) obtained during drying were Aspergillus spp., and the remaining (n = 25, 26.05%) belonged to other genera, such as Penicillium, Trichoderma and Cladosporium. Grape juice-based agar medium was used to determine the realistic OTA production capacities of the isolated mould strains. The highest OTA production capacities were 809.70 ± 9.19, 87.58 ± 16.89 and 45.44 ± 18.78 ng g(-1) in 50% grape juice agar (GJ50), all five of which were from A. niger isolates. OTA was not present in any sample during the drying period; however, OTA was detected in two samples at 0.32 ± 0.15 and 0.52 ± 0.36 µg kg(-)(1) after the end of the drying process. The limit of detection (LOD) and limit of quantitation (LOQ) of the method used for detecting OTA in samples were 0.1 and 0.3 µg kg(-)(1), respectively.

Quantification of Aspergillus carbonarius in grapes using a real time PCR assay

A study on the representation of Aspergillus carbonarius in the vineyards of the Mesogeia geographical region of Attica, Greece, was conducted. One hundred and twenty five samples of the indigenous drought and disease resistant Savatiano wine grape variety, the most widely planted in Greece, were collected. The sample's total DNA extracts were initially tested for fungal DNA presence by targeting the Internal Transcribed Spacer (ITS) region in end-point Polymerase Chain Reactions. Samples which were proved positive were further subjected to PCR analysis using specific primers targeting an A. carbonarius polycetide synthase (pks) gene. Among ITS positive samples (70%), A. carbonarius was represented in 42% of them. Furthermore, a SYBR Green I Real Time PCR method was used to quantify the amount of this species in the grape samples. The values of the positive samples were estimated in the range of 13 to 50 × 10(3) fungal haploid genomes/g grapes. The significance of this study lies in the applicability of a rapid and culture-independent method to detect and quantify A. carbonarius on grapes.

Microbiological food safety and a low-microbial diet to protect vulnerable people

Low-microbial diets are advised by many institutions for people with neutropenia resulting from treatment with immunosuppressive drugs or medical conditions that increase their susceptibility to foodborne disease. In this article, the main microbiological hazards associated with foods are outlined, and a low-microbial diet in which higher-risk foods are replaced by lower-risk foods is described.