A review on the occurrence and control of ochratoxigenic fungal species and ochratoxin A in dehydrated grapes, non-fortified dessert wines and dried vine fruit in the Mediterranean area

Comprehensive Insights into Ochratoxin A: Occurrence, Analysis, and Control Strategies

Ochratoxin A (OTA) is a toxic mycotoxin produced by some mold species from genera Penicillium and Aspergillus. OTA has been detected in cereals, cereal-derived products, dried fruits, wine, grape juice, beer, tea, coffee, cocoa, nuts, spices, licorice, processed meat, cheese, and other foods. OTA can induce a wide range of health effects attributable to its toxicological properties, including teratogenicity, immunotoxicity, carcinogenicity, genotoxicity, neurotoxicity, and hepatotoxicity. OTA is not only toxic to humans but also harmful to livestock like cows, goats, and poultry. This is why the European Union and various countries regulate the maximum permitted levels of OTA in foods. This review intends to summarize all the main aspects concerning OTA, starting from the chemical structure and fungi that produce it, its presence in food, its toxicity, and methods of analysis, as well as control strategies, including both fungal development and methods of inactivation of the molecule. Finally, the review provides some ideas for future approaches aimed at reducing the OTA levels in foods.

A label-free colorimetric 3D paper-based device for ochratoxin A detection using G-quadruplex/hemin DNAzyme with a smartphone readout

The colorimetric sensor usually depends on enzyme-mediated signal amplification to achieve trace analysis of ochratoxin A (OTA) residues in food samples. However, the enzyme labeling and manual addition of reagents steps increased assay time and operation complexity, restricting their application in point-of-care testing (POCT). Herein, we report a label-free colorimetric device integrating a 3D paper-based analytical device and a smartphone as handheld readout for rapid and sensitive detection of OTA. Using vertical-flow design, the paper-based analytical device enables the specific recognition of target and self-assembly of G-quadruplex (G4)/hemin DNAzyme to be performed, then employs DNAzyme for transducing the OTA binding event signal into a colorimetric signal. The design of independent functional units, including biorecognition unit, self-assembly unit and colorimetric units, which can address crowding and disorder of biosensing interfaces and improve the recognition efficiency of aptamer (apta). In addition, we eliminated signal losses and nonuniform coloring by introducing carboxymethyl chitosan (CMCS) to obtain perfectly focused signals on colorimetric unit. On the basis of parameter optimization, the device exhibited a detection range of 0.1-500 ng/mL and a detection limit of 41.9 pg/mL for OTA. Importantly, good results were obtained in spiked real samples, indicating applicability and reliability of developed device.

Quantitative and qualitative analysis of ochratoxin-A using fluorescent CQDs@DNA-based nanoarchitecture assembly to monitor food safety and quality

Ochratoxin A (OTA), a mycotoxin formed by various fungi, such as Aspergillus and Penicillium species, is dangerous to human health. Thus, to circumvent the risk of OTA ingestion, the recognition and quantification of OTA levels are of great significance. A perusal of the literature has revealed that the integration of DNA/Carbon Quantum Dot (CQD)-based hybrid systems may exhibit the unique electronic and optical properties of nanomaterials/nanoarchitecture and consequent recognition properties. Herein, we developed the CQDs@DNA-based hybrid nanoarchitecture system for the selective detection of OTA, which exhibits modulation in the emission spectrum after interaction with OTA, with a significant binding constant (K_a = 3.5 × 10⁵ M^-1), a limit of detection of 14 nM, limit of quantification of 47 nM and working range of 1-10 μM. The mechanism for sensing the OTA has been corroborated using fluorescence, UV-visible absorption spectroscopy, and FTIR techniques, demonstrating the binding mode of CQD@DNA hybrid nano-architecture assembly with OTA. Further, we demonstrated the sensing ability of developed CQDs@DNA-based nanoarchitecture assembly towards the quantification of OTA in real food monitoring analysis for real-time applications, which makes this developed nanoarchitecture assembly the potential candidate to conveniently monitor food safety and quality for human health.

From Grapes to Wine: Impact of the Vinification Process on Ochratoxin A Contamination

Ochratoxin A (OTA) is one of the major mycotoxins, classified as "potentially carcinogenic to humans" (Group 2B) by the International Agency for Research on Cancer (IARC), and wine is one of its main sources of intake in human consumption. The main producer of this toxin is Aspergillus carbonarius, a fungus that contaminates grapes early in the growing season. The vinification process, as a whole, reduces the toxin content in wine compared to the grapes; however, not all vinification steps contribute equally to this reduction. During the maceration phase in red wines, toxin concentrations generally tend to increase. Based on previous studies, this review provides an overview of how each step of the vinification process influences the final OTA contamination in wine. Moreover, certain physical, chemical, and microbiological post-harvest strategies are useful in reducing OTA levels in wine. Among these, the use of fining agents, such as gelatin, egg albumin, and bentonite, must be considered. Therefore, this review describes the fate of OTA during the winemaking process, including quantitative data when available, and highlights actions able to reduce the final OTA level in wine.

Current Review of Mycotoxin Biodegradation and Bioadsorption: Microorganisms, Mechanisms, and Main Important Applications

Mycotoxins are secondary metabolites produced by fungi. Food/feed contamination by mycotoxins is a great threat to food safety. The contamination can occur along the food chain and can cause many diseases in humans and animals, and it also can cause economic losses. Many detoxification methods, including physical, chemical, and biological techniques, have been established to eliminate mycotoxins in food/feed. The biological method, with mycotoxin detoxification by microorganisms, is reliable, efficient, less costly, and easy to use compared with physical and chemical ones. However, it is important to discover the metabolite's toxicity resulting from mycotoxin biodegradation. These compounds can be less or more toxic than the parent. On the other hand, mechanisms involved in a mycotoxin's biological control remain still unclear. Mostly, there is little information about the method used by microorganisms to control mycotoxins. Therefore, this article presents an overview of the most toxic mycotoxins and the different microorganisms that have a mycotoxin detoxification ability. At the same time, different screening methods for degradation compound elucidation are given. In addition, the review summarizes mechanisms of mycotoxin biodegradation and gives some applications.

Urinary Biomarkers of Mycotoxin Induced Nephrotoxicity-Current Status and Expected Future Trends

The intensifying world-wide spread of mycotoxigenic fungal species has increased the possibility of mycotoxin contamination in animal feed and the human food chain. Growing evidence shows the deleterious toxicological effects of mycotoxins from infants to adults, while large population-based screening programs are often missing to identify affected individuals. The kidney functions as the major excretory system, which makes it particularly vulnerable to nephrotoxic injury. However, few studies have attempted to screen for kidney injury biomarkers in large, mycotoxin-exposed populations. As a result, there is an urgent need to screen them with sensitive biomarkers for potential nephrotoxicity. Although a plethora of biomarkers have been tested to estimate the harmful effects of a wide spectrum of toxicants, β₂-microglobulin (β₂-MG) and N-acetyl-β-D-glucosaminidase (NAG) are currently the dominant biomarkers employed routinely in environmental toxicology research. Nevertheless, kidney injury molecule 1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL) are also emerging as useful and informative markers to reveal mycotoxin induced nephrotoxicity. In this opinion article we consider the nephrotoxic effects of mycotoxins, the biomarkers available to detect and quantify the kidney injuries caused by them, and to recommend biomarkers to screen mycotoxin-exposed populations for renal damage.

The Occurrence and Contamination Level of Ochratoxin A in Plant and Animal-Derived Food Commodities

Ochratoxin A (OTA) is a highly toxic mycotoxin and poses great threat to human health. Due to its serious toxicity and widespread contamination, great efforts have been made to evaluate its human exposure. This review focuses on the OTA occurrence and contamination level in nine plant and animal derived food commodities: cereal, wine, coffee, beer, cocoa, dried fruit, spice, meat, and milk. The occurrence and contamination level varied greatly in food commodities and were affected by many factors, including spices, geography, climate, and storage conditions. Therefore, risk monitoring must be routinely implemented to ensure minimal OTA intake and food safety.

An Aptamer-Array-Based Sample-to-Answer Biosensor for Ochratoxin A Detection via Fluorescence Resonance Energy Transfer

Food toxins are a hidden threat that can cause cancer and tremendously impact human health. Therefore, the detection of food toxins in a timely manner with high sensitivity is of paramount importance for public health and food safety. However, the current detection methods are relatively time-consuming and not practical for field tests. In the present work, we developed a novel aptamer-chip-based sample-to-answer biosensor (ACSB) for ochratoxin A (OTA) detection via fluorescence resonance energy transfer (FRET). In this system, a cyanine 3 (Cy3)-labeled OTA-specific biotinylated aptamer was immobilized on an epoxy-coated chip via streptavidin-biotin binding. A complementary DNA strand to OTA aptamer at the 3′-end was labeled with a black hole quencher 2 (BHQ2) to quench Cy3 fluorescence when in proximity. In the presence of OTA, the Cy3-labeled OTA aptamer bound specifically to OTA and led to the physical separation of Cy3 and BHQ2, which resulted in an increase of fluorescence signal. The limit of detection (LOD) of this ACSB for OTA was 0.005 ng/mL with a linearity range of 0.01–10 ng/mL. The cross-reactivity of ACSB against other mycotoxins, ochratoxin B (OTB), aflatoxin B1 (AFB1), zearalenone (ZEA), or deoxynilvalenol (DON), was less than 0.01%. In addition, this system could accurately detect OTA in rice samples spiked with OTA, and the mean recovery rate of the spiked-in OTA reached 91%, with a coefficient of variation (CV) of 8.57–9.89%. Collectively, the ACSB may represent a rapid, accurate, and easy-to-use platform for OTA detection with high sensitivity and specificity.

Occurrence and impact of fungicides residues on fermentation during wine production- A review

Continuous fungicide spraying is required to eliminate fungal pathogens on grapes. However, this practice is associated with several risks, including contamination and environmental imbalance, as well as toxicity to operators and the induction of resistance in pathogens. In addition, a strong correlation has been reported between the presence of fungicides and the occurrence of issues during alcoholic fermentation, resulting in negative impacts on the sensory quality of the final products. Numerous studies have evaluated residue concentrations of phytosanitary products in grapes, juices, and wines, and a significant number of studies have assessed the impact of different agrochemicals on bioprocesses. However, a review compiling the key results of these studies is currently lacking. This review incorporates results obtained in the last decade from research on the presence of fungicide residues, including azoxystrobin, boscalid, captan, copper, fenhexamid, folpet, pyraclostrobin, pyrimethanil and tebuconazole, and their effects on fermentation kinetics. Practical solutions to mitigate these problems, both in vineyards and industry, are also presented and discussed. This review highlights the constant high fungicidal agent concentrations (greater than 1 or 2 mg L^-1) used throughout the winemaking process, with the impact of residues being of particular concern, especially with regard to their effect on yeast activity and the fermentation process. Thus, the adoption of methodologies that allow winemakers to control and trace these residues is an important step in avoiding or reducing fermentation problems throughout the winemaking process.[Figure: see text].

Antifungal activity of Saccharomyces cerevisiae and assessment of ochratoxigenic load on currants by means of Real Time PCR

Currants are prone to contamination by ochratoxin during cultivation, processing and storage conditions. Saccharomyces cerevisiae is considered to be among the main species of grape yeast flora able to control antagonistic fungi. In this study, the potential of S. cerevisiae Y₃₃ was investigated to inhibit the growth of several fungal species indigenous to the microbiota of grapes. Moreover, the efficacy of this yeast species was investigated to inhibit OTA by toxin producing fungi both in vitro and in situ. For this purpose thirty-five different fungal species, belonging to the genera Aspergillus, Penicillium, Cladosporium, Fusarium and Alternaria interacted in vitro with S. cerevisiae on Malt Extract agar plates, stored at 25 °C for 14 days. Results showed that the highest OTA producer A. carbonarius F₇₁ was inhibited more than 99% from day 7, in contrast to A. niger strains that presented enhanced OTA production at day 14 due to interaction with S. cerevisiae Y₃₃. Additionally, the antifungal potential of the selected yeast was also studied in situ on currants subjected to different treatments and stored at 25 °C for 28 days. Microbiological analysis was undertaken for the enumeration of the bacterial and fungal flora, together with OTA determination at 7 and 21 days. To quantify A. carbonarius on all treated currant samples, molecular analysis with Real Time PCR was employed. A standard curve was prepared with A. carbonarius DNA. The efficiency of the curve was estimated to 10.416, the slope to -3.312 and the range of haploid genome that could be estimated was from 1.05 to 105∙10⁵. The amount of A. carbonarius DNA in all treated currants samples, where the fungus was positively detected, ranged from as low as 0.08 to 562 ng DNA/g currants. The antifungal activity of S. cerevisiae Y₃₃ was observed in all studied cases, causing inhibition of fungal growth and OTA production.

Recent progress in determination of ochratoxin a in foods by chromatographic and mass spectrometry methods

Ochratoxin A is a highly toxic mycotoxin and has posed great threat to human health. Due to its serious toxicity and wide contamination, great efforts have been made to develop reliable determination methods. In this review, analytical methods are comprehensively summarized in terms of sample preparation strategy and instrumental analysis. Detailed method is described according to the food commodities in the order of cereal, wine, coffee, beer, cocoa, dried fruit and spice. This review mainly focuses on the recent advances, especially reported in the last decade. At last, challenges and perspectives are also discussed to achieve better advancement and promote practical application in this field.

Functional roles of LaeA, polyketide synthase, and glucose oxidase in the regulation of ochratoxin A biosynthesis and virulence in Aspergillus carbonarius

Aspergillus carbonarius is the major producer of ochratoxin A (OTA) among Aspergillus species, but the contribution of this secondary metabolite to fungal virulence has not been assessed. We characterized the functions and addressed the roles of three factors in the regulation of OTA synthesis and pathogenicity in A. carbonarius: LaeA, a transcriptional factor regulating the production of secondary metabolites; polyketide synthase, required for OTA biosynthesis; and glucose oxidase (GOX), regulating gluconic acid (GLA) accumulation and acidification of the host tissue during fungal growth. Deletion of laeA in A. carbonarius resulted in significantly reduced OTA production in colonized nectarines and grapes. The ∆laeA mutant was unable to efficiently acidify the colonized tissue, as a direct result of diminished GLA production, leading to attenuated virulence in infected fruit compared to the wild type (WT). The designed Acpks-knockout mutant resulted in complete inhibition of OTA production in vitro and in colonized fruit. Interestingly, physiological analysis revealed that the colonization pattern of the ∆Acpks mutant was similar to that of the WT strain, with high production of GLA in the colonized tissue, suggesting that OTA accumulation does not contribute to A. carbonarius pathogenicity. Disruption of the Acgox gene inactivated GLA production in A. carbonarius, and this mutant showed attenuated virulence in infected fruit compared to the WT strain. These data identify the global regulator LaeA and GOX as critical factors modulating A. carbonarius pathogenicity by controlling transcription of genes important for fungal secondary metabolism and infection.

Host Factors Modulating Ochratoxin A Biosynthesis during Fruit Colonization by Aspergillus carbonarius

Aspergillus carbonarius is a strong and consistent ochratoxin A (OTA) producer and considered to be the main source of this toxic metabolite in grapes and grape products such as wine, grape juice and dried vine fruit. OTA is produced under certain growth conditions and its accumulation is affected by several environmental factors, such as growth phase, substrate, temperature, water activity and pH. In this study, we examined the impact of fruit host factors on regulation and accumulation of OTA in colonized grape berries, and assessed in vitro the impact of those factors on the transcriptional levels of the key genes and global regulators contributing to fungal colonization and mycotoxin synthesis. We found that limited sugar content, low pH levels and high malic acid concentrations activated OTA biosynthesis by A. carbonarius, both in synthetic media and during fruit colonization, through modulation of global regulator of secondary metabolism, laeA and OTA gene cluster expression. These findings indicate that fruit host factors may have a significant impact on the capability of A. carbonarius to produce and accumulate OTA in grapes.

Control of Penicillium glabrum by Indigenous Antagonistic Yeast from Vineyards

Biocontrol is one of the most promising alternatives to synthetic fungicides for food preservation. Botrytis cinerea, Alternaria alternata, and Aspergillus section Nigri are the most concerning pathogens for grape development. However, frequently, other species, such as Penicillium glabrum in this study, are predominant in spoiled bunches. In this work, 54 native yeasts from vineyards were screened by direct confrontation in potato dextrose agar plates as antagonists against P. glabrum. Isolates of Pichia terricola, Aureobasidium pullulans, and Zygoascus meyerae were selected for their antagonist activity in vitro, plus isolates of Pichia kudriavzevii, Hormonema viticola, and Hanseniaspora uvarum were used as negative controls. However, in vivo, confrontations in wounded grapes showed disagreement with direct confrontation in vitro. P. terricola, P. kudriavzevii, H. viticola, Z. meyerae, and H. uvarum significantly reduced the incidence of P. glabrum on grapes. Nevertheless, P. terricola, H. viticola, and H. uvarum themselves spoiled the wounded grapes. Inhibitions were associated with different mechanisms such as the production of volatile organic compounds (VOCs), lytic enzymes, biofilm formation, and competition for nutrients. The isolates of P. kudriavzevii L18 (a producer of antifungal VOCs which completely inhibited the incidence of P. glabrum) and Z. meyerae L29 (with pectinase, chitinase and β-glucanase activity and biofilm formation which reduced 70% of the incidence of P. glabrum) are proposed as suitable biocontrol agents against P. glabrum.

Amplified Fluorescent Aptasensor for Ochratoxin A Assay Based on Graphene Oxide and RecJf Exonuclease

In this study, we developed an aptamer-based fluorescent sensing platform for the detection of ochratoxin A (OTA) based on RecJ_f exonuclease-assisted signal amplification and interaction between graphene oxide (GO) and the OTA aptamer (OTA-apt). After optimizing the experimental conditions, the present aptamer-based sensing system can exhibit excellent fluorescent response in the OTA assay, with a limit of detection of 0.07 ng/mL. In addition to signal amplification, this strategy is also highly specific for other interfering toxins. Furthermore, this aptasensor can be reliably used for assessing red wine samples spiked with different OTA concentrations (2.4, 6 and 20 ng/mL). The proposed assay plays an important role in the field of food safety and can be transformed for detecting other toxins by replacing the sequence that recognizes the aptamer.

The Influence of NaCl and Glucose Content on Growth and Ochratoxin A Production by Aspergillus ochraceus, Aspergillus carbonarius and Penicillium nordicum

Ochratoxin A (OTA) is a nephrotoxic mycotoxin, which deserves particular attention for its widespread contamination of a variety of food and feed. Aspergillus ochraceus, Aspergillus carbonarius, and Penicillium nordicum are an important source of OTA in three different kinds of food commodities, including cereals, grape and dried fruit products, and dry-cured meat products. Deeper knowledge of OTA production and mycelium growth related to the high-sugar or NaCl-rich environments was gained in this manuscript. A. ochraceus and P. nordicum were likely to have greater growth rates in medium supplied with certain concentrations of NaCl (0–80 g/L), and the colony diameter was the largest at the salt content of 40 g/L. P. nordicum was more suitable to grow in NaCl-riched medium, the OTA production was increased to 316 ppb from 77 ppb when 20 g/L NaCl was added. The capability of OTA production was inhibited when salt content was 40 g/L and 60 g/L in A. ochraceus and P. nordicum, respectively. As the glucose content increased to 250 g/L, the capacity of mycelium growth and sporulation was increased significantly in A. ochraceus and A. carbonarius. A. carbonarius was more suitable to grow in high-sugar grape products. OTA production was significantly promoted with an added 100 g/L glucose in A. carbonarius. OTA production was inhibited when glucose content was 150 g/L and in 200 g/L in A. ochraceus and A. carbonarius, respectively. NaCl and glucose have an effect on fungal growth and OTA production, and the activation of biosynthetic genes of OtaA. These results would allow designing new strategies to prevent OTA accumulation on sugar or NaCl-riched foodstuffs and achieve the objective to manufacture cereals, dried vine fruits and dry-cured ham, free of OTA.

Dark field microscope-based single nanoparticle identification coupled with statistical analysis for ultrasensitive biotoxin detection in complex sample matrix

A novel approach for ultrasensitive ochratoxin A (OTA) detection is reported based on dark field microscope-based single nanoparticle identification coupled with a statistical analysis method. OTA aptamers were firstly hybridized with a single-stranded DNA (DNA1) to form an identification probe (DNA1-Apt). The aptamers separate from DNA1 in the presence of OTA and are released from the identification probe. Then, another single-stranded DNA (DNA2) hybridizes with DNA1 and result in the aggregation of gold nanoparticles (AuNPs). Therefore, the presence of AuNP aggregates is the evidence of the presence of OTA, while AuNP aggregates can be easily identified together with the monomers under dark field microscopic inspection. On the other hand, by counting the aggregation rate (the number of AuNP aggregates versus the number of AuNP monomers) with a statistical analysis method, OTA could be quantitatively detected. The detection range for OTA was 0.1 pg/mL ~ 30 ng/mL and the limit of detection was 0.1 pg/mL. The proposed sensor has comparative detection performance to sensors utilizing a number of signal amplification procedures, with the additional advantages of simplicity and high efficiency. The sensor can also be adopted for other target detection simply by replacing the identification probes. Graphical abstract The schematic of the AuNP aggregation for OTA detection. The OTA aptamers were competitively banded by OTA and induced form AuNP aggregation after adding DNA2 and AuNPs2. Subsequently, AuNPs were detected under dark field microscope and statistical analysis.

Ochratoxigenic fungi and Ochratoxin A determination in dried grapes marketed in Tunisia

Purpose

With the present work, we aimed to assess the occurrence of ochratoxigenic fungi and Ochratoxin A (OTA) in dried grapes from Tunisia.

Methods

Dried grapes samples (n = 90) were investigated for the presence of ochratoxigenic fungi, which were further characterized at the species level through amplification of the internal transcribed spacer (ITS) region and polymerase chain reaction (PCR) product sequencing. Fungal isolates were tested for their ochratoxigenic potential by high-performance liquid chromatography with fluorescence detection (HPLC-FLD), as well as dried grapes samples after an immunoaffinity column (IAC) clean-up procedure.

Results

Black Aspergilli isolates were the dominant genre among the filamentous fungi found in dried grapes samples and were the only OTA-producing fungi encountered. Aspergillus niger aggregate were the most frequently found isolates reaching 70%, 80%, and 85% in dried grapes samples from regions of Kelibia, Sfax, and Rafraf, respectively, while covered 100% of the relevant mycobiota found in imported samples. Aspergillus carbonarius isolates were found only in Sfax’s and Kelibia’s samples, while uniseriate Aspergilli were found between 7 and 20% in dried grapes from Kelibia, Sfax, and the imported samples. The in vitro OTA production test showed that 88.9% of OTA-producing isolates belonged to A. carbonarius with OTA levels varying from 0.06 to 1.32 μg/g of Czapek Yeast Agar (CYA). The remaining OTA-producing fungi (11.1 %) belonged to A. niger aggregate group having a maximum OTA potential of 2.88 μg/g CYA, and no uniseriate Aspergilli isolate was able to produce OTA. All dried grapes samples were free of OTA presence.

Conclusion

According to the present study’s findings, no OTA contamination was recorded in the investigated samples from Tunisian market. Nevertheless, the presence of strong OTA producers A. carbonarius in samples originated from the two out of three studied Tunisian regions, as well the high incidences of Aspergillus niger aggregate group with an attested potential for OTA production in all samples, necessitates further research on Tunisian dried grapes. Additionally, a continuous analysis of staple food of the Mediterranean diet is imperative to insure the best quality for the consumers and prevent potential health problems.

Persistent luminescence nanorod based luminescence resonance energy transfer aptasensor for autofluorescence-free detection of mycotoxin

Serious ochratoxin A (OTA) contamination necessitates the development of rapid, sensitive and selective analytical methods for its determination in food safety. Herein, we report a persistent luminescence resonance energy transfer (LRET) based aptasensor for the autofluorescence-free detection of OTA. OTA aptamer functionalized persistent luminescence nanorod (PLNR) Zn₂GeO₄:Mn²⁺ and the aptamer complementary DNA modified gold nanoparticle (AuNP) were used as the donor and the acceptor, respectively. The developed LRET aptasensor integrated the advantages of the long-lasting persistent luminescence of PLNR, the high selectivity of aptamer and the low probe background of LRET sensors, allowing autofluorescence-free detection of OTA in biological samples with high sensitivity and selectivity. The developed LRET aptasensor gave an excellent linearity in the range of 0.01-10 ng mL^-1, the detection limit of 3 pg mL^-1 and the precision of 2.7% (RSD, n = 11) at 1 ng mL^-1 level. The applicability of the developed aptasensor was demonstrated by analyzing beer samples for OTA with the recoveries of 92.3%-104%.

Effects of Curcumin on the Renal Toxicity Induced by Ochratoxin A in Rats

Ochratoxin A (OTA) is a powerful nephrotoxin and the severity of its damage to kidneys depends on both the dose and duration of exposure. According to the scientific data currently available, the mechanism of action still is not completely clarified, but it is supposed that oxidative stress is responsible for OTA-induced nephrotoxicity. Bioactive compound use has emerged as a potential approach to reduce chronic renal failure. Therefore, curcumin (CURC), due to its therapeutic effects, has been chosen for our study to reduce the toxic renal effects induced by OTA. CURC effects are examined in Sprague Dawley rats treated with CURC (100 mg/kg), alone or in combination with OTA (0.5 mg/kg), by gavage daily for 14 days. The end result of the experiment finds rats treated with OTA show alterations in biochemical and oxidative stress parameters in the kidney, related to a decrease in the Glomerular Filtration Rate (GFR). Conversely, the administration of CURC attenuates oxidative stress and prevents glomerular hyperfiltration versus the OTA group. Furthermore, kidney histological tests show a reduction in glomerular and tubular damage, inflammation and tubulointerstitial fibrosis. This study shows that CURC can mitigate OTA-induced oxidative damage in the kidneys of rats.

Toxicological and Medical Aspects of Aspergillus-Derived Mycotoxins Entering the Feed and Food Chain

Due to Earth's changing climate, the ongoing and foreseeable spreading of mycotoxigenic Aspergillus species has increased the possibility of mycotoxin contamination in the feed and food production chain. These harmful mycotoxins have aroused serious health and economic problems since their first appearance. The most potent Aspergillus-derived mycotoxins include aflatoxins, ochratoxins, gliotoxin, fumonisins, sterigmatocystin, and patulin. Some of them can be found in dairy products, mainly in milk and cheese, as well as in fresh and especially in dried fruits and vegetables, in nut products, typically in groundnuts, in oil seeds, in coffee beans, in different grain products, like rice, wheat, barley, rye, and frequently in maize and, furthermore, even in the liver of livestock fed by mycotoxin-contaminated forage. Though the mycotoxins present in the feed and food chain are well documented, the human physiological effects of mycotoxin exposure are not yet fully understood. It is known that mycotoxins have nephrotoxic, genotoxic, teratogenic, carcinogenic, and cytotoxic properties and, as a consequence, these toxins may cause liver carcinomas, renal dysfunctions, and also immunosuppressed states. The deleterious physiological effects of mycotoxins on humans are still a first-priority question. In food production and also in the case of acute and chronic poisoning, there are possibilities to set suitable food safety measures into operation to minimize the effects of mycotoxin contaminations. On the other hand, preventive actions are always better, due to the multivariate nature of mycotoxin exposures. In this review, the occurrence and toxicological features of major Aspergillus-derived mycotoxins are summarized and, furthermore, the possibilities of treatments in the medical practice to heal the deleterious consequences of acute and/or chronic exposures are presented.

Red orange and lemon extract prevents the renal toxicity induced by ochratoxin A in rats

In this work, we investigated the effects of red orange and lemon extract (RLE) on ochratoxin A (OTA)-induced nephrotoxicity. In particular, we analyzed the change in renal function and oxidative stress in Sprague-Dawley rats treated with OTA (0.5 mg/kg body weight, b.w.) and with RLE (90 mg/kg b.w.) by oral administration. After OTA treatment, we found alterations of biochemical and oxidative stress parameters in the kidney, related to a severe decrease of glomerular filtration rate. The RLE treatment normalized the activity of antioxidant enzymes and prevented the glomerular hyperfiltration. Histopathological examinations revealed glomerular damages and kidney cortex fibrosis in OTA-rats, while we observed less severe fibrosis in OTA plus RLE group. Then, we demonstrated that oxidative stress could be the cause of OTA renal injury and that RLE reduces this effect.

Preparation and evaluation of highly hydrophilic aptamer-based hybrid affinity monolith for on-column specific discrimination of ochratoxin A

Nonspecific adsorption is a challenge of specific recognition on aptamer-based affinity monoliths. Here, a novel highly hydrophilic polyhedral oligomeric silsesquioxane (POSS)-containing aptamer-based hybrid-silica affinity monolith with a good recognition nature was prepared and used for specific discrimination of ochratoxin A (OTA). A homogeneous polymerization mixture consisted of POSS chemicals, hydrophilic monomers and aptamer solution was directly polymerized via the "one-pot" method. Preparation and characterization of the resultant affinity monolith were studied in detail. A highly hydrophilic nature was obtained and the typical hydrophilic interaction liquid chromatography (HILIC) was observed when acetonitrile (ACN) content in mobile phase was 25%, which reached the highest hydrophilicity of POSS-based hybrid monoliths. By using OTA as model analyte, the nonspecific adsorption was effectively suppressed. The recovery of the analogue ochratoxin B (OTB) was only about 0.1% even if the content of OTB was 50 times more than OTA, which was much better than other POSS-containing monoliths and polar siloxane-based hybrid monoliths. Applied to beer samples, the adsorption of background materials was drastically resisted, and efficient recognition of OTA was obtained with the recoveries of 94.9-99.8%. Much less disturbance was observed than that occurred in hydrophobic POSS-based affinity monolith. It lights an attractive implement with high hydrophilicity and specificity for online selective recognition of OTA.

A fluorescent aptasensor for ochratoxin A detection based on enzymatically generated copper nanoparticles with a polythymine scaffold

A fluorescence enhancement method is presented for the determination of ochratoxin A (OTA). The interaction of OTA with its aptamer causes structural changes which, in turn, change fluorescence of enzymatically generated polythymine-coated copper nanoparticles (CuNPs) (with excitation/emission maxima at 340/625 nm). The OTA-binding aptamer was immobilized on magnetic beads. When it binds OTA, it is partially released and exposes a region with a partly complimentary DNA strand (cDNA). After magnetic separation, the cDNA was employed as a primer to trigger the terminal deoxynucleotidyl transferase-mediated polymerization. This process generates polythymine which act as a template for synthesis of the CuNPs. The method is sensitive in having a 2.0 nM detection limit for OTA. It was successfully applied to the determination of OTA in spiked diluted red wine. Graphical abstract Schematic presentation of a fluorometric enhancement method for ochratoxin A assay based on ochratoxin A inducing structure switching of its aptamer and enzymatically generated polythymine for copper nanoparticles formation.

Aptamer-Based Fluorometric Ochratoxin A Assay Based on Photoinduced Electron Transfer

This study describes a novel quencher-free fluorescent method for ochratoxin A (OTA) detection based on the photoinduced electron transfer (PIET) between guanine and fluorophore. In the absence of OTA, carboxyfluorescein (FAM)-labeled aptamer can partly hybridize with the complementary strand of OTA aptamer (OTA-cAPT), which contains four guanines at its 3′-end. As a result, the fluorescence of FAM is quenched due to PIET and stacked guanines. In the presence of OTA, FAM-labeled OTA aptamer can bind specifically to OTA, and thereby the high fluorescence intensity of the dye can be maintained. Under the optimal conditions, the method had a detection limit of 1.3 nM. In addition, the method we proposed is highly sensitive and specific for OTA. Furthermore, the method was proven to be reliable based on its successful application in the detection of OTA in red wine samples. Therefore, this promising, facile, and quencher-free method may be applied to detect other toxins by using other appropriate aptamers.

Comprehensive study on the degradation of ochratoxin A in water by spectroscopic techniques and DFT calculations

The OTA degradation process becomes irreversible only if, following hydrolyzation of the lactone ring, the molecule fragments.

Effect of potassium sorbate (E-202) and the antifungal PgAFP protein on Aspergillus carbonarius growth and ochratoxin A production in raisin simulating media

BACKGROUND

Ochratoxin A (OTA) is a mycotoxin produced by several species of Aspergillus and Penicillium fungi. The presence of OTA in raisins is mainly related to black Aspergillus spp. contamination. This toxin poses risks to human and animal health due to its high toxicity and carcinogenicity. New strategies to avoid the risk associated with OTA are therefore necessary.

RESULTS

A comparison was made between the effects of the antifungal protein PgAFP and potassium sorbate (E-202) on the growth of Aspergillus carbonarius, biosynthetic- and stress-related gene expression and its OTA production at two water activity (a_w ) levels, 0.95 and 0.93 a_w . The results showed that PgAFP successfully controlled OTA production, whereas E-202, despite being able to reduce Aspergillus carbonarius growth, caused a significant increase in OTA production by the fungus.

CONCLUSION

PgAFP protein, a biological compound with an antifungal activity, is safer to use than E-202 and may be proposed as a food preservative and a useful strategy to control ochratoxigenic A. carbonarius in raisins. © 2018 Society of Chemical Industry.

Evaluation of behaviour of Lachancea thermotolerans biocontrol agents on grape fermentations

Previous researches have showed that Lachancea thermotolerans strains RCKT4 and RCKT5 inhibited the growth of Aspergillus. However, currently, there are no data on their nutritional preferences, as a possible substrate competitor against Saccharomyces cerevisiae, and their effects on fermentation. In this work, we observed that the biocontrol yeasts and S. cerevisiae BSc203, based on the utilization of 16 carbonate sources, revealed significant differences in the nutritional profile (biocontrol yeasts NS:0·25, BSc203 NS:0·56). Lachancea thermotolerans strains did not occupy the same niche as that of BSc203 (NOI:0·44). The biocontrol agents and BSc203 presented similar competitive attitude in terms of the sugar, ethanol and sulphite tolerances. During fermentation, the biocontrol yeasts were found to tolerate up to 12% v/v ethanol, 250 mg ml^-1 of total SO₂ and 30° Brix sugar. In mixed cultures, L. thermotolerans strains did not negatively affect the growth of BSc203 and the wine quality, except when RCKT4 was initially inoculated at a high proportion in the mixed culture 1MSK4 (1%BSc203/99%RCKT4), resulting in a lower production of CO₂ and ethanol, in comparison with pure BSc203. RCKT5, at a high proportion, in 1MSK5 (1%BSc203/99%RCKT5) presented promising oenological properties. This fermentation showed lower acetic acid contents and higher total acidity than pure BSc203.

SIGNIFICANCE AND IMPACT OF THE STUDY

Generally it is not evaluated if the biofungicide yeasts sprayed on vegetables alter the quality of the fermented products. This work focused on the importance of assessing the possible effects of yeast-based fungicides used in vineyards on grape fermentation, especially on Saccharomyces cerevisiae growth. In this context, the competition between biofungicide yeasts and S. cerevisiae under winemaking conditions is investigated.

Risk management of ochratoxigenic fungi and ochratoxin A in maize grains by bioactive EVOH films containing individual components of some essential oils

Aspergillus steynii and Aspergillus tubingensis are possibly the main ochratoxin A (OTA) producing species in Aspergillus section Circumdati and section Nigri, respectively. OTA is a potent nephrotoxic, teratogenic, embryotoxic, genotoxic, neurotoxic, carcinogenic and immunosuppressive compound being cereals the first source of OTA in the diet. In this study bioactive ethylene-vinyl alcohol copolymer (EVOH) films containing cinnamaldehyde (CINHO), linalool (LIN), isoeugenol (IEG) or citral (CIT) which are major components of some plant essential oils (EOs) were produced and tested against A. steynii and A. tubingensis growth and OTA production in partly milled maize grains. Due to the favourable safety profile, these bioactive compounds are considered in the category "GRAS". The study was carried out under different water activity (0.96 and 0.99 a_w), and temperature (24 and 32 °C) conditions. ANOVA showed that class of film, fungal species, a_w and temperature and their interactions significantly affected growth rates (GR), ED₅₀ and ED₉₀ and the doses for total fungal growth inhibition and OTA production. The most effective EVOH films against both species were those containing CINHO. ED₅₀, ED₉₀ and doses for total growth and OTA inhibition were 165-405, 297-614, 333-666 μg of EVOH-CINHO/plate (25 g of maize grains), respectively, depending on environmental conditions. The least efficient were EVOH-LIN films. ED₅₀, ED₉₀ and doses for total growth and OTA inhibition were 2800->3330, >3330 and >3330 μg of EVOH-LIN/plate (25 g of maize grains), respectively. The effectiveness of the bioactive films increased with increasing doses. Overall, A. tubingensis was less sensitive to treatments than A. steynii. Depending on the species, a_w and temperature affected GR and OTA production in a different way. In A. steynii cultures, optimal growth occurred at 0.96 a_w and 32 °C while optimal OTA production happened at 0.99 a_w and 32 °C. In A. tubingensis cultures optimal growth happened at 0.99 a_w and 32 °C, although the best conditions for OTA production were 0.99 a_w and 24 °C. Thus, these species can be very competitive in warm climates and storage conditions. The EVOH-CINHO films followed by EVOH-IEG and EVOH-CIT films, designed in this study and applied in vapour phase, can be potent antifungal agents against A. steynii and A. tubingensis and strong inhibitors of OTA biosynthesis in maize grains at very low doses. This is the first study on the impact that interacting environmental conditions and bioactive films containing individual components of EOs have on the growth of these ochratoxigenic fungi and on OTA production in maize grains.

High-performance and versatile electrochemical aptasensor based on self-supported nanoporous gold microelectrode and enzyme-induced signal amplification

Herein, novel and versatile electrochemical aptasensors were constructed on a self-supported nanoporous gold (np-Au) microelectrode, integrating with an exonuclease III (Exo III) induced signal amplification strategy. Self-supported np-Au microelectrode with 3D bicontinuous nanoporous structures possesses tremendously large specific area, clean surface, high stability and biocompatibility, bringing about significant advantages in both molecular recognition and signal response. As paradigms, two analytes of bisphenol A (BPA) and ochratoxin A (OTA) were selected to demonstrate the superiority and versatility of designed aptasensors. Trace amounts of mDNA (associated with BPA or OTA concentration) hybridized with cDNA strands assembled on np-Au microelectrode, activating the cleavage reaction with Exo III. Thus, cDNA was digested and mDNA was released to undergo a new hybridization and cleavage cycle. Finally, residual cDNA strands were recognized by methylene blue labelled rDNA/AuNPs with the assistance of hDNA to generate the electrochemical signals, which were used to quantitatively monitor targets. Under the optimized conditions, prepared aptasensors exhibited wide linear ranges (25pg/mL to 2ng/mL for BPA, 10pg/mL to 5ng/mL for OTA) with ultralow detection limits (10pg/mL for BPA, 5pg/mL for OTA), excellent selectivity and stability, and reliable detection in real samples. This work opens a new horizon for constructing promising electrochemical aptasensors for environmental monitoring, medical diagnostics and food safety.

Raisins and Currants as Conventional Nutraceuticals in Italian Market: Natural Occurrence of Ochratoxin A

The healthy consumers make a strong pressure to natural products that can prevent the chronic diseases and improve the general health status, and therefore an important aspect that have to be considered is the safe level of the nutraceuticals. This study reports the occurrence of Ochratoxin A (OTA) and associated fungal contamination in 35 samples of dried vine fruits imported in the European community potentially used for the development of new nutraceutical supplements. High pressure liquid chromatography analysis identified 18 samples as contaminated by OTA with an average level of 2.6 μg/kg. OTA was measured in 4 samples of currants (mean value of 6.6 μg/kg) and 13 samples of raisins (mean value of 1.4 μg/kg). In one sample of currants and one of raisins from Turkey OTA exceeded the limits set by European Commission of 10 μg/kg, being contaminated with 12.61 and 15.99 μg/kg, respectively. All the positive samples were confirmed by Orbitrap Q Exactive through their molecular weight and the corresponding fragmentation. The worldwide consumption of dried vine fruits contributed to OTA exposure in several group of consumers. In particular, considering the potential nutraceutical approach, this consumption may be represent a severe risk for healthy consumers that consider these products like healthy and salutistic for their contents in antioxidants, flavonoids, and polyphenols. Data reported in this study confirmed the need to regularly monitor mycotoxin levels in these food products and optimize the process of fruits drying in order to reduce the development of toxigenic molds.

Silver Nanoparticle-Based Fluorescence-Quenching Lateral Flow Immunoassay for Sensitive Detection of Ochratoxin A in Grape Juice and Wine

A silver nanoparticle (AgNP)-based fluorescence-quenching lateral flow immunoassay with competitive format (cLFIA) was developed for sensitive detection of ochratoxin A (OTA) in grape juice and wine samples in the present study. The Ru(phen)32+-doped silica nanoparticles (RuNPs) were sprayed on the test and control line zones as background fluorescence signals. The AgNPs were designed as the fluorescence quenchers of RuNPs because they can block the exciting light transferring to the RuNP molecules. The proposed method exhibited high sensitivity for OTA detection, with a detection limit of 0.06 µg/L under optimized conditions. The method also exhibited a good linear range for OTA quantitative analysis from 0.08 µg/L to 5.0 µg/L. The reliability of the fluorescence-quenching cLFIA method was evaluated through analysis of the OTA-spiked red grape wine and juice samples. The average recoveries ranged from 88.0% to 110.0% in red grape wine and from 92.0% to 110.0% in grape juice. Meanwhile, less than a 10% coefficient variation indicated an acceptable precision of the cLFIA method. In summary, the new AgNP-based fluorescence-quenching cLFIA is a simple, rapid, sensitive, and accurate method for quantitative detection of OTA in grape juice and wine or other foodstuffs.

Transcriptional Analysis of Acinetobacter sp. neg1 Capable of Degrading Ochratoxin A

Ochratoxin A (OTA) is a nephrotoxic and potentially carcinogenic mycotoxin produced by several species of Aspergillus and Penicillium, contaminating grapes, wine and a variety of food products. We recently isolated from OTA contaminated soil vineyard a novel free-living strain of Acinetobacter sp. neg1, ITEM 17016, able to degrade OTA into the non-toxic catabolic product ochratoxin α. Biochemical studies suggested that the degradation reaction proceeds via peptide bond hydrolysis with phenylalanine (Phe) release. In order to identify genes responsible for OTA degradation we performed a differential gene expression analysis of ITEM 17016 grown in the presence or absence of the toxin. Among the differentially expressed genes, six peptidases up-regulated at 6 h were identified. The degrading activity of the carboxypeptidase PJ_1540 was confirmed in vitro in a heterologous system. The enrichment analysis for Gene Ontology terms confirmed that OTA degradation proceeds through peptidase activities and revealed the over-representation of pathways related to Phe catabolism. These results indicate that Phe may represent an energy source for this Acinetobacter sp. neg1 strain and that OTA degrading reaction triggers the modulation of further catabolic activities.

Amino acid functionalized ZrO2 nanoparticles decorated reduced graphene oxide based immunosensor

Here, a study is reported on a simple, one-step method for the synthesis of a zirconium dioxide–reduced graphene oxide (ZrO₂–RGO) nanocomposite and its functionalization with amino acid to develop an immunosensor for detection of ochratoxin A.

Grape and environmental mycoflora monitoring in old, traditionally cultivated vineyards on Mount Etna, southern Italy

BACKGROUND

Grape contamination by several fungal species occurs during a vineyard's preharvest and harvest. Agronomic management and microclimatic conditions can affect fungi occurrence and epidemiology, thus explaining qualitative differences in mycoflora composition, including the presence of phytopathogenic or mycotoxigenic fungi. In this study a two-year grape, air and soil mycoflora monitoring programme was undertaken in vineyards on Mount Etna (eastern Sicily, Italy). The mycoflora composition was investigated at pea berry and veraison phenological phases from air and soil and at ripening from sample grapes.

RESULTS

Mycoflora in air and soil varied according to the phenological stage. In the air samples, penicillia were dominant over aspergilli at the pea berry phase, but their ratio was inverted at early veraison. Black aspergilli (BA) were isolated from the vine environment and grape samples, where BA were represented mainly by Aspergillus niger aggregate, which showed no or low ochratoxin A (OTA) production. Aspergillus carbonarius was either not identified or identified at low frequency, although most of the isolates produced OTA.

CONCLUSION

Monitoring focused on the environmental mycoflora composition and highlighted the good health profile of various Sicilian autochthonous grape cultivars. In addition, data suggest that the lower relative humidity occurring at the highest altitudes reduces BA incidence. © 2016 Society of Chemical Industry.

Plant Food Supplements with Antioxidant Properties for the Treatment of Chronic and Neurodegenerative Diseases: Benefits or Risks?

Wine by-products, in particular grape pomace, can be an important source of polyphenols and dietary fibers and are increasingly being used as a starting material in the industrial production of plant food supplements, such as other matrices containing biomolecules, with antioxidant properties. The risk associated with the consumption of these products was recently analyzed through a study of potential genotoxic and carcinogenic compounds that can be found in the marketed products. In particular, occurrence data about contamination with the mycotoxin ochratoxin A were also reported. This short review aims at giving an overview about the quality and benefits of these kinds of food supplements, and also about risks of incorrect use, focusing on the emerging need for stricter European regulations.

Screening and Identification of Novel Ochratoxin A-Producing Fungi from Grapes

Ochratoxin A (OTA) contamination has been established as a world-wide problem. In this study, the strains with the ability of OTA production were screened by analyzing the green fluorescence of the isolates colonies from the grapes in Zhenjiang with 365 nm UV light and confirmed by HPLC with fluorescent detection (HPLC-FLD). The results showed that seven isolates acquired the characteristic of the fluorescence, of which only five showed the ability of OTA production as confirmed by HPLC-FLD analysis. The five OTA-producing strains were identified based on comparative sequence analysis of three conserved genes (ITS, BenA and RPB2) of the strains, and they are Talaromyces rugulosus (O1 and Q3), Penicillium commune (V5-1), Penicillium rubens (MQ-5) and Aspergillus aculeatus (MB1-1). There are two Penicillium species of the five OTA-producing strains and our study is the first to report that P. rubens, T. rugulosus and A. aculeatus can produce OTA. This work would contribute to comprehensively understanding the fungi with an OTA-producing ability in grapes before harvest and then take effective measures to prevent OTA production.