Ochratoxin A (OTA) contamination and the associated issues of food security, food safety and economic loss are widespread throughout the world. The occurrence of OTA depends on ochratoxigenic fungi, foodstuffs and their environment. In this review, natural occurrence and control strategy of OTA, with a focus on the impact of environmental factors, are summarized. First, this manuscript introduces potentially contaminated foodstuffs, including the emerging ones which are not regulated in international legislation. Secondly, it gives an update of native producers based on foodstuffs and OTA biosynthesis. Thirdly, complicated environmental regulation is disassembled into individual factors in order to clarify their regulatory effect and mechanism. Finally, to emphasize control OTA at all stages of foodstuffs from farm to table, strategies used at crop planting, harvest, storage and processing stages are discussed.

In this paper we analyse the impact of temperature variations in the design of an Operational Transconductance Amplifier (OTA) based on CNTFET, where the active load is a cascode current sink mirror. In particular we determine the Voltage Transfer Characteristics (VTCs) and the Common Mode Rejection Ratio (CMRR) at different temperatures.

Ochratoxin A (OTA) is a well-known mycotoxin with wide distribution in food and feed. Fungal genome sequencing has great utility for identifying secondary metabolites gene clusters for known and novel compounds. A comparative analysis of the OTA-biosynthetic cluster in A. steynii, A. westerdijkiae, A. niger, A. carbonarius, and P. nordicum has revealed a high synteny in OTA cluster organization in five structural genes (otaA, otaB, ota, otaR1, and otaD). Moreover, a recent detailed comparative genome analysis of Aspergilli OTA producers led to the identification of a cyclase gene, otaY, located in the OTA cluster between the otaA and otaB genes, encoding for a predicted protein with high similarity to SnoaLs domain. These proteins have been shown to catalyze ring closure steps in the biosynthesis of polyketide antibiotics produced in Streptomyces. In the present study, we demonstrated an upregulation of the cyclase gene in A. carbonarius under OTA permissive conditions, consistent with the expression trends of the other OTA cluster genes and their role in OTA biosynthesis by complete gene deletion. Our results pointed out the involvement of a cyclase gene in OTA biosynthetic pathway for the first time. They represent a step forward in the understanding of the molecular basis of OTA biosynthesis in A. carbonarius.

The widespread use of Next-Generation Sequencing (NGS) for fungal genome sequencing has led to identification of SM clusters for known metabolites as well as a significant number of novel predicted SM gene clusters. Fungal genome sequencing has great utility for identification of secondary metabolites gene clusters for known as well as novel compounds. Ochratoxin A (OTA) is a well-known mycotoxin with wide distribution on food and feed. A comparative analysis of gene cluster structure in 19 Aspergillus and 2 Penicillium OTA producers has revealed a high synteny across these species in OTA cluster, encoding five structural genes: otaA, otaB, otaC, otaR1, and otaD. Furthermore, we identify a previously undescribed additional gene. The new otaY gene is located between the otaA and otaB genes and encodes a protein with predicted SnoaL domain. These snoaL-domain containing proteins have been shown to catalyze ring closure steps in the biosynthesis of polyketide antibiotics produced in Streptomyces. Gene expression analysis has demonstrated an upregulation of the cyclase gene in A. carbonarius under OTA permissive conditions, consistent with the expression trends of the other OTA cluster genes. The role of in OTA biosynthesis has been demonstrated by CRISPR/Cas9 complete gene deletion. The presented results reveal for the first time the involvement of a cyclase gene in OTA biosynthetic pathway and redefine the structure of the OTA core cluster, consisting in six genes.

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Aspergillus niger and A. tubingensis, species belonging to section Nigri, are commonly found in plant products and processed food, such as grapes, cereals, coffee and derivatives. These two species are very difficult to differentiate by classical morphological criteria and some isolates are known to produce ochratoxin A. The exact identification of these two species is very important to avoid overestimation of toxicological contamination and related risks. A PCR-based identification and detection assay was developed as tool to identify A. niger and A. tubingensis, using molecular differences obtained by sequencing the calmodulin gene. Two pairs of species-specific primers were designed and empirically evaluated for PCR identification of A. niger and A. tubingensis. Species-specific PCR products generated by each primer set were 505 bp (A. tubingensis) and 245 bp (A. niger) in length, which could be potentially useful for a multiplex PCR assay. The sensitivity of this assay was about 10 pg DNA in 25 µl PCR reaction volume, using pure total DNA of the two species. The method described in this study represents a rapid and reliable procedure to assess the presence in food products of two ochratoxigenic species of section Nigri.