OTA-producing fungi in foodstuffs: A review

Construction of dual-signal output sensing platform for different scene of rapid and sensitive ochratoxin A detection in corn

Photoelectrochemical (PEC) is a highly sensitive and fast analytical method that can be used at low concentrations, while photoelectrochromic is a simple and low-cost method primarily utilized for high concentration detection. Therefore, we have developed a dual-signal output sensing platform based on both PEC and photoelectrochromism for rapid and sensitive OTA detection. The sensing platform is divided into signal generation (SG) region and signal output (SO) region, which modified with WO3/BiVO4 photoactive nanocomposites and polyaniline (PANI), respectively. By irradiating the SG region, photogenerated electrons are generated and injected into the SO region through the conductive pathway, resulting in a decrease in surface blue polyaniline and a change to green. The smart device can accurately measure the RGB-Green values, enabling the construction of a photochromic visual sensing platform. After immobilizing the OTA aptamer in the SG region, a linear correlation was observed between the concentration of OTA and the RGB-Green value within the range of 20 ng/L ∼250 μg/L. The detection limit was determined to be 8.33 ng/L (S/N = 3). Furthermore, for a more sensitive OTA detection, a PEC sensing platform was developed utilizing the SG region as a photoanode, exhibiting a linear correlation in the range of 2 pg/L∼300 μg/L with a detection limit of 0.8 pg/L (S/N = 3). The detection of these two modes under the requirement of the international standard for the maximum limit realizes the sensitive OTA detection. The RGB-Green is verified to PEC signal, which improves the detection accuracy. The sensing platform has several advantages and is suitable for various application scenarios.

The Global Secondary Metabolite Regulator AcLaeA Modulates Aspergillus carbonarius Virulence, Ochratoxin Biosynthesis, and the Mode of Action of Biopesticides and Essential Oils

Aspergillus carbonarius is considered one of the main fungi responsible for black and sour rot in grapes, as well as the production of the carcinogenic mycotoxin ochratoxin A. The global regulatory methyltransferase protein LaeA controls the production of various secondary metabolites in Aspergillus species, as well as influences sexual and asexual reproduction and morphology. The goal of this study was to investigate the role of the regulatory gene AclaeA in physiology, virulence, and ochratoxin A (OTA) production by deleting this gene from the genome of a wild-type A. carbonarius strain. The evaluation data on the morphological characteristics, virulence experiments in three different grape varieties, and OTA analysis of ΔAclaeA mutants showed that the growth and the OTA production by ΔAclaeA strains were significantly reduced. The mutant strains were also less virulent, producing 40-50% less conidia in three different cultivars of grape berries. Additionally, the gene AclaeA was considerably repressed after the application of three commercial biopesticides (Trianum-P®, Vacciplant®, and Serenade® Max) and the essential oils (EOs) cinnamon, geranium, and thyme, which were also shown to inhibit OTA biosynthesis in A. carbonarius. The study of the regulatory gene AclaeA can contribute to a broader understanding of the role of secondary metabolites during A. carbonarius-grape interactions, as well as the discovery of the mode of action of biological plant protection products and EOs against this mycotoxigenic fungus.

Biological and Chemical Management of Aspergillus carbonarius and Ochratoxin A in Vineyards

Ochratoxin A (OTA) is a widely distributed mycotoxin and potent carcinogen produced by several fungal genera, but mainly by Aspergillus carbonarius. Grape contamination occurs in vineyards during the period between veraison and pre-harvest, and it is the main cause of OTA's presence in wine. The aim of the current study was the evaluation of 6 chemical and 11 biological plant protection products (PPPs) and biocontrol agents in commercial vineyards of the two important Greek white wine varieties cv. Malagousia and cv. Savatiano. The PPPs were applied in a 4-year vineyard study as single treatments or/and in combinations as part of IPM systems. Subsequently, nine strains of Aspergillus carbonarius were investigated for their sensitivity against seven active compounds of synthetic fungicides. During the multi-year field trials, various novel management systems, including consortia of biocontrol agents, were revealed to be effective against Aspergillus sour rot and OTA production. However, expected variability was observed in the experimental results, indicating the dynamic character of biological systems and highlighting the possible inconsistency of PPPs' efficacy in a changing environment. Furthermore, the IPM systems developed effectuated an optimized control of A. carbonarius, leading to 100% inhibition of OTA contamination, showing the importance of using both chemical and biological PPPs for disease management and prevention of fungal fungicide resistance. Finally, the majority of A. carbonarius tested strains were found to be sensitive against the pure active compounds used (fludioxonil, azoxystrobin, chlorothalonil, tebuconazole, cyprodinil, pyrimethanil and boscalid), with only a few exceptions of developed resistance towards boscalid.

Ochratoxin A in food commodities: A review of occurrence, toxicity, and management strategies

Ochratoxin A (OTA) is a potent mycotoxin produced by species of Aspergillus and Penicillium that contaminate agricultural products and pose significant health risks to both humans and animals. This review examines the mechanisms of OTA toxicity, its occurrence in various food commodities, and the implications for public health and trade. Literature pertaining to OTA was sourced from Google Scholar, covering the period from 2004 to 2024. OTA exposure is linked to multiple adverse health effects, including teratogenicity, immunotoxicity, and hepatotoxicity, with a primary impact on kidney function, and it is classified as a possible human carcinogen (Group 2B). Its toxic effects are attributed to several mechanisms, including lipid peroxidation, inhibition of protein synthesis, DNA damage, oxidative stress, and mitochondrial dysfunction. Notable findings included the presence of OTA in 46.7 % of cocoa products in Turkey, 32 % of cocoa samples in Côte d'Ivoire exceeding the OTA threshold of 2 μg/kg, and 91.5 % of ready-to-sell cocoa beans in Nigeria testing positive for OTA. Coffee beans are particularly susceptible to OTA contamination, which underscores the need for vigilant monitoring. Additionally, OTA contamination impacts agricultural productivity and food safety, leading to significant economic consequences, particularly in regions reliant on exports, such as cocoa and coffee. Several countries regulate the OTA levels in food products to safeguard public health. However, these regulations can impede trade, particularly in countries with high levels of contamination. Balancing regulatory compliance with economic viability is crucial for affected nations. Current strategies for managing OTA include improved agronomic practices, such as the use of biocontrol agents for pest management, enhanced storage conditions to prevent mould growth, and the implementation of detoxification techniques to reduce OTA levels in food products. Despite these strategies, OTA remains a significant threat to public health and the agricultural economy worldwide. The complexity of contamination in food products requires robust prevention, control, and management strategies to mitigate its impact. Continuous research and regulatory initiatives are essential for safeguarding consumers and ensuring food safety.

Assessment of Fungal and Contamination of Ochratoxin A and Patulin in Foods Susceptible to Contamination in the Yangzhou Market, China

The conducive conditions of warm and humid climates can facilitate mold proliferation and subsequent mycotoxin production during food processing and distribution, thereby posing a potential risk to consumer health. However, there exists a significant lack of research regarding the diversity of molds and the presence of ochratoxin A (OTA) and patulin (PAT) in food products available in the Yangzhou market. This study was conducted to assess OTA contamination levels and fungal presence in 57 cereal-based food samples, as well as PAT contamination levels and fungal presence in 50 types of foods, including apples, hawthorn berries, pears, and their derivatives. Ochratoxin A (OTA) was detected in 17 out of 57 cereal-based food samples, with concentrations ranging from 0.93 to 32.69 μg/kg. The contamination rate was determined to be 31.48%, and no samples exceeded the established regulatory limits. Furthermore, seven apple products were identified as contaminated with patulin (PAT), exhibiting concentrations between 26.85 and 192.78 μg/kg. Additionally, three food samples derived from hawthorn showed PAT contamination levels ranging from 29.83 to 88.56 μg/kg. Through purification on potato dextrose agar (PDA) medium, observation of colony morphology, and analysis of internal transcribed spacer (ITS) sequences, a total of 35 fungal strains belonging to 13 genera were identified in cereal-based foods. The predominant genera in cereals included Talaromyces, Fusarium, Aspergillus, and Penicillium. Additionally, twelve fungal strains from five genera (Penicillium, Cladosporium, Aureobasidium, Curvularia, and Alternaria) were isolated and identified in fruits and their derivatives. The findings indicate that OTA and PAT toxins are one of the important risk factors that threaten consumer health. Furthermore, the contamination of some other toxigenic strains is also a matter of substantial concern, with potential implications for consumer health.

Biocontrol of Occurrence Ochratoxin A in Wine: A Review

Viticulture has been an important economic sector for centuries. In recent decades, global wine production has fluctuated between 250 and almost 300 million hectoliters, and in 2022, the value of wine exports reached EUR 37.6 billion. Climate change and the associated higher temperatures could favor the occurrence of ochratoxin A (OTA) in wine. OTA is a mycotoxin produced by some species of the genera Aspergillus and Penicillium and has nephrotoxic, immunotoxic, teratogenic, hepatotoxic, and carcinogenic effects on animals and humans. The presence of this toxin in wine is related to the type of wine-red wines are more frequently contaminated with OTA-and the geographical location of the vineyard. In Europe, the lower the latitude, the greater the risk of OTA contamination in wine. However, climate change could increase the risk of OTA contamination in wine in other regions. Due to their toxic effects, the development of effective and environmentally friendly methods to prevent, decontaminate, and degrade OTA is essential. This review summarises the available research on biological aspects of OTA prevention, removal, and degradation.

Effective degradation of zearalenone by dye-decolorizing peroxidases from Pleurotus ostreatus and its metabolic pathway and toxicity analysis

The widespread detection of zearalenone (ZEN) in cereal crops and feeds poses a significant threat to both humans and animals. Consequently, the urgency for the international community to address this issue is evident in the demand for safe and effective measures to mitigate zearalenone contamination and explore detoxification methods. In this study, a dye-decolorizing peroxidase (PoDyP4) from Pleurotus ostreatus is characterized for its impressive ZEN degradation effectiveness. PoDyP4 was demonstrated that the ability to almost completely degrade ZEN at pH 6.0 and 40 °C for 2 h, even at high concentrations of 1 mM. The promotion of enzymatic degradation of ZEN was most pronounced in the presence of Mg2+, while Cu2+ and Fe2+ exhibited a notable inhibitory effect. The degradation mechanism elucidated the detoxification of ZEN by PoDyP4 through hydroxylation and polymerization reactions. The resulting metabolic products displayed significantly reduced toxicity and minimal impact on the viability and apoptosis of mouse spermatocytes GC-2 cells, in comparison to the original ZEN. Hydrophobic contacts and hydrogen bonds were found to be crucial for ZEN-PoDyP4 stability via molecular docking. This finding suggests that PoDyP4 may have a promising application in the field of food and feed for zearalenone detoxification.

Occurrence and impact of carbendazim and hymexazol residues on yeast growth and ochratoxin A contamination during wine production

BACKGROUND

Grapes are highly vulnerable to infection by carbon black aspergilli, which produce ochratoxin A (OTA), a mycotoxin. Carbendazim and hymexazol are widely applied to control grape diseases. Howerver, fungicides, toxigenic fungi, and OTA can be transferred from grapes to wine causing potential safety issues. The impact of these residues on fungal populations and OTA during vinification are currently unclear. Here we investigated the effects of carbendazim and hymexazol on the viability of Aspergillus carbonarius and OTA contamination during an indoor wine-processing experiment.

RESULTS

The population size of A. carbonarius substantially increased at 24 h followed by a significantly decreased at 72 h after destemming and crushing. However, carbendazim and hymexazol notably inhibited the growth of A. carbonarius in must samples. In addition, yeast growth was substantially deleyed by carbendazim, hymexazol, and OTA during the first 3 days in compared with the control. Carbendazim, hymexazol, and OTA residues declined over time, and the processing factors (PFs) for carbendazim and hymexazol throughout vinification were 0.164, 0.074, and 0.185-0.476, respectively. Carbendazim and hymexazol each reduced OTA concentrations. However, there was no significant difference after 48 h. Addition of carbendazim or hymexazol significantly reduced the level of A. carbonarius but had no significant effect on the final concentration of OTA in mature wine.

CONCLUSION

The wine-making process can reduce the residues of OTA, carbendazim, and hymexazol in grapes, but it is recommended that grapes chosen to make wine should be free of A. carbonarius contamination. © 2023 Society of Chemical Industry.

Comparative Study of Ochratoxin A Exposure through the Intake of Cereal Products in Two Climatic Moroccan Regions

The present study aims to compare ochratoxin A (OTA) exposure through the intake of three cereal derivative products (bread, pasta and semolina) in two different Moroccan climatic regions (littoral and continental). OTA weekly intakes from cereal products were calculated using a deterministic approach for each region. Results showed a statistically significant difference (p < 0.05) of OTA exposure between the two regions. Indeed, the median OTA exposure was estimated at 48.97 ng/kg b.w./week in the littoral region, while it was estimated at 6.36 ng/kg b.w./week in the continental region. The probabilistic approach showed that, due to uncertainties, the 95th percentile of weekly OTA exposure associated with the three cereal products ranged from 66.18 to 137.79 (95% CI) with a median of 97.44 ng/kg body weight (b.w.)/week. Compared to the threshold of 100 ng/kg b.w./week, 95% of the cumulative distributions predicted an exceedance frequency between 0.42 and 17.30% (95% CI), with an exceedance frequency median of 4.43%. Results showed that cereal derivatives constitute an important vector of OTA exposure and cause a significant exceedance of toxicological reference value among large consumers in the littoral region, which suggests the urgency of reconsidering the maximum regulatory limit (MRL) set for OTA (3 µg/kg) in cereal derivatives by Moroccan authorities.

A label-free fluorescent aptasensor based on a novel exponential rolling circle amplification for highly sensitive ochratoxin A detection

Rapid and sensitive analysis of ochratoxin A (OTA) plays an important role in food safety. Here, an aptasensor based on novel exponential rolling circle amplification (ERCA) was proposed for ultrasensitive and label-free fluorescence detection of OTA. The attachment of OTA to its aptamer could release H and rapidly hybridize with CT to initiate rolling circle amplification (RCA). The amplicons could further displace H from APH to initiate recycled RCA, achieving exponential growth of amplification products that contained G4 dimers for lighting up ThT. Benefiting from the exponential amplification efficiency of the ERCA strategy and the high fluorescence quantum yield of G4 dimer/ThT, this strategy exhibited a wide linear range from 10 fg/mL to 10 ng/mL with a detection limit of 4.3 fg/mL. In addition, the aptasensor displayed satisfactory recoveries in real sample analysis. We believe that this novel aptasensor possesses promising application prospects in food safety and medicine detection.

Characteristic Structures of Different Stilbenes Distinguish the Impact on Ochratoxin A Biosynthesis Intermediate Pathway and Metabolites of Aspergillus carbonarius

In this paper, we accurately pinpointed the inhibition sites of ochratoxin A (OTA) synthesis pathway in Aspergillus carbonarius acted by stilbenes from the perspective of oxidative stress and comprehensively explored the relationship between the physical and chemical properties of natural polyphenolic substances and their biochemical properties of antitoxin. To facilitate the application of ultra-high-performance liquid chromatography and triple quadrupole mass spectrometry for real-time tracking of pathway intermediate metabolite content, the synergistic effect of Cu²⁺-stilbenes self-assembled carriers was utilized. Cu²⁺ increased the generation of reactive oxygen species to accumulate mycotoxin content, while stilbenes had the inhibitory effect. The impact of the m-methoxy structure of pterostilbene on A. carbonarius was found to be superior to that of resorcinol and catechol. The m-methoxy structure of pterostilbene acted on the key regulator Yap1, downregulated the expression of antioxidant enzymes, and accurately inhibited the halogenation step of the OTA synthesis pathway, thus accumulating the content of OTA precursors. This provided a theoretical basis for the extensive and efficient application of a wide range of natural polyphenolic substances for postharvest disease control and quality assurance of grape products.

The Effect of Mushroom Culture Filtrates on the Inhibition of Mycotoxins Produced by Aspergillus flavus and Aspergillus carbonarius

Two of the mycotoxins of greatest agroeconomic significance are aflatoxin B1 (AFB1), and ochratoxin A (OTA). It has been reported that extracts from some wood-decaying mushrooms, such as Lentinula edodes and Trametes versicolor showed the ability to inhibit AFB1 or OTA biosynthesis. Therefore, in our study, a wide screening of 42 isolates of different ligninolytic mushrooms was assayed for their ability to inhibit the synthesis of OTA in Aspergillus carbonarius and AFB1 in Aspergillus flavus, in order to find a metabolite that can simultaneously inhibit both mycotoxins. The results showed that four isolates produce metabolites able to inhibit the synthesis of OTA, and 11 isolates produced metabolites that inhibited AFB1 by >50%. Two strains, the Trametes versicolor strain TV117 and the Schizophyllum commune strain S.C. Ailanto, produced metabolites able to significantly inhibit (>90%) the synthesis of both mycotoxins. Preliminary results suggest that the mechanism of efficacy of the S. commune rough and semipurified polysaccharides could be analogous to that found previously for Tramesan®, by enhancing the antioxidant response in the target fungal cells. The overall results indicate that S. commune’s polysaccharide(s) could be a potential agent(s) in biological control and/or a useful component of the integrated strategies able to control mycotoxin synthesis.

Impact of environmental factors on ochratoxin A: From natural occurrence to control strategy

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.

Lactic Acid Bacteria as Potential Agents for Biocontrol of Aflatoxigenic and Ochratoxigenic Fungi

Aflatoxins (AF) and ochratoxin A (OTA) are fungal metabolites that have carcinogenic, teratogenic, embryotoxic, genotoxic, neurotoxic, and immunosuppressive effects in humans and animals. The increased consumption of plant-based foods and environmental conditions associated with climate change have intensified the risk of mycotoxin intoxication. This study aimed to investigate the abilities of eleven selected LAB strains to reduce/inhibit the growth of Aspergillus flavus, Aspergillus parasiticus, Aspergillus carbonarius, Aspergillus niger, Aspergillus welwitschiae, Aspergillus steynii, Aspergillus westerdijkiae, and Penicillium verrucosum and AF and OTA production under different temperature regiments. Data were treated by ANOVA, and machine learning (ML) models able to predict the growth inhibition percentage were built, and their performance was compared. All factors LAB strain, fungal species, and temperature significantly affected fungal growth and mycotoxin production. The fungal growth inhibition range was 0-100%. Overall, the most sensitive fungi to LAB treatments were P. verrucosum and A. steynii, while the least sensitive were A. niger and A. welwitschiae. The LAB strains with the highest antifungal activity were Pediococcus pentosaceus (strains S11sMM and M9MM5b). The reduction range for AF was 19.0% (aflatoxin B1)-60.8% (aflatoxin B2) and for OTA, 7.3-100%, depending on the bacterial and fungal strains and temperatures. The LAB strains with the highest anti-AF activity were the three strains of P. pentosaceus and Leuconostoc mesenteroides ssp. dextranicum (T2MM3), and those with the highest anti-OTA activity were Leuconostoc paracasei ssp. paracasei (3T3R1) and L. mesenteroides ssp. dextranicum (T2MM3). The best ML methods in predicting fungal growth inhibition were multilayer perceptron neural networks, followed by random forest. Due to anti-fungal and anti-mycotoxin capacity, the LABs strains used in this study could be good candidates as biocontrol agents against aflatoxigenic and ochratoxigenic fungi and AFL and OTA accumulation.

Characterization of Bacillus velezensis E2 with abilities to degrade ochratoxin A and biocontrol against Aspergillus westerdijkiae fc-1

Ochratoxin A (OTA), primarily produced by the fungi belonging to the species of Aspergillus and Penicillium, is one of the most common mycotoxins found in cereals and fruits. In addition to resulting in huge economic losses, OTA contamination also poses considerable threat to human and livestock health. Microbial degradation of mycotoxins has been considered with great potential in mycotoxins decontamination. In a previous study, Bacillus velezensis E2 was isolated by our laboratory and showed appreciable inhibitory effect on Aspergillus flavus growth and aflatoxin production in rice grains. In this study, B. velezensis E2 was investigated for its ability to remove OTA and biocontrol against the ochratoxigenic Aspergillus westerdijkiae fc-1. The results revealed that B. velezensis E2 has considerable inhibitory effect on A. westerdijkiae fc-1 both on PDA medium and pear fruits, with inhibitory rate of 51.7% and 73.9%, respectively. In addition, its ability to remove OTA was evaluated in liquid medium and the results showed that more than 96.1% of OTA with an initial concentration of 2.5 μg/mL could be removed by B. velezensis E2 in 48 h. Further experiments revealed that enzymatic transformation and alkaline hydrolysis might be the main mechanisms related to OTA degradation by B. velezensis E2, with ring open ochratoxin α (OP-OTα) as a possible degradation product. Our study indicated that the B. velezensis E2 strain could be a potential bacterial candidate in biodegradation of OTA and biocontrol against A. westerdijkiae fc-1.

Antifungal Mechanisms and Application of Lactic Acid Bacteria in Bakery Products: A Review

Bakery products are nutritious, but they are susceptible to fungal contamination, which leads to a decline in quality and safety. Chemical preservatives are often used to extend the shelf-life of bakery products, but long-term consumption of these preservatives may increase the risk of chronic diseases. Consumers increasingly demand food with fewer chemical preservatives. The application of lactic acid bacteria (LAB) as a novel biological preservative not only prolongs the shelf-life of bakery products but also improves the baking properties of bakery products. This review summarizes different types and action mechanisms of antifungal compounds produced by LAB, factors affecting the production of antifungal compounds, and the effects of antifungal LAB on bakery products, providing a reference for future applications of antifungal LAB in bakery products.

Contamination, Detection and Control of Mycotoxins in Fruits and Vegetables

Mycotoxins are secondary metabolites produced by pathogenic fungi that colonize fruits and vegetables either during harvesting or during storage. Mycotoxin contamination in fruits and vegetables has been a major problem worldwide, which poses a serious threat to human and animal health through the food chain. This review systematically describes the major mycotoxigenic fungi and the produced mycotoxins in fruits and vegetables, analyzes recent mycotoxin detection technologies including chromatography coupled with detector (i.e., mass, ultraviolet, fluorescence, etc.) technology, electrochemical biosensors technology and immunological techniques, as well as summarizes the degradation and detoxification technologies of mycotoxins in fruits and vegetables, including physical, chemical and biological methods. The future prospect is also proposed to provide an overview and suggestions for future mycotoxin research directions.

Removal of Ochratoxin A from Red Wine Using Alginate-PVA-L. plantarum (APLP) Complexes: A Preliminary Study

The presence of ochratoxin A (OTA) in wines is a problem mainly due to the health damage it can cause to frequent drinkers. A method for removing these toxic substances from wine is the use of lactic acid bacteria with mycotoxin-adsorption capacities; however, their use is limited since a matrix in which they can be immobilized, to remove them after use, is needed. In this study, L. plantarum (LP) was encapsulated in a polymeric matrix composed of polyvinyl alcohol (PVA) and alginate, forming alginate–PVA–LP (APLP) complexes. Then, these complexes were characterized, and assays of OTA and phenol removal from wines were performed. As a result, it was observed that the APLP complexes at a concentration of 0.5 g mL⁻¹ removed over 50% of the OTA without substantially affecting the concentration of total phenols. In addition, it was determined that the presence of L. plantarum directly affected the ability to adsorb OTA from wines and did not decrease the total phenols. In conclusion, an alginate–PVA matrix allows immobilizing LP, and the complexes formed are an alternative for removing ochratoxin from contaminated wines.

Deletion and Overexpression of the AnOTAbzip Gene, a Positive Regulator of Ochratoxin A Biosynthesis in Aspergillus niger

The ochratoxin A (OTA) biosynthetic gene cluster includes a bZIP transcription factor (TF) gene (OTAbzip) that has been identified in different fungal species. However, most previous studies identified the OTAbzip gene in ochratoxigenic fungi using bioinformatics methods, while few studies focused on deleting the gene, let alone overexpressing it, to characterize the function of the OTAbZIP TF. Here, we characterized the AnOTAbZIP TF in an ochratoxigenic isolate of Aspergillus niger by deleting and overexpressing the AnOTAbzip gene and examining the role of AnOTAbZIP in morphological development, OTA biosynthesis, and pathogenicity. Chemical and gene expression analyses revealed that AnOTAbZIP positively regulates OTA biosynthesis, since the loss of OTA production and the downregulation of the OTA biosynthetic genes were observed in the ΔAnOTAbzip strain, compared with the wild-type (WT) and OE::AnOTAbzip strains. In terms of pathogenicity, the ΔAnOTAbzip strain produced a greater lesion on grape berries, especially with respect to the OE::AnOTAbzip strain, rather than WT. Finally, the ΔAnOTAbzip strain was also more tolerant to oxidative stress with respect to the OE::AnOTAbzip and WT strains in that order. These new findings improve our understanding of the AnOTAbZIP regulatory mechanism and help develop strategies to attenuate plant pathogenicity and reduce OTA biosynthesis of A. niger.

Ochratoxin A: Occurrence and recent advances in detoxification

Ochratoxin A (OTA), one of the most important mycotoxins, is mainly produced by fungi in the genera Aspergillus and Penicillium, and commonly found in food and agricultural products. In addition to causing significant economic losses, the occurrence of OTA in foods poses a serious threat to human health. Therefore, it is very important to develop approaches to control or detoxify OTA contamination and thus ensure food safety. In this paper, we review the source and occurrence of OTA in food and agricultural products and the latest achievements in the removal and detoxification of OTA using physical, chemical, and biological methods, with specific attention to influencing factors and mechanisms related to the biodetoxification of OTA. Moreover, the advantages and disadvantages of these methods and their potential application prospect were also discussed.

Polyols Induce the Production of Antifungal Compounds by Lactobacillus plantarum

Mycotoxins may be present in nuts, coffee, cereals, and grapes, among other products. Increasing concerns about human health and environmental protection have driven the application of biological control techniques that can inhibit fungal contaminants. In this study, the growth inhibition of the ochratoxigenic fungus Aspergillus carbonarius Ac 162 was evaluated using 5 lactic acid bacteria (LAB). The LAB studied were Lactobacillus plantarum MZ801739 (J), Lactobacillus plantarum MZ809351 (31) and Lactobacillus plantarum MZ809350 (34), isolated in the Ivory Coast, and Lactobacillus plantarum MN982928 (3) and Leuconostoc citreum MZ801735 (23), isolated in Mexico. J, 31, 34, 3 and 23 are the internal strain codes from our laboratory. LAB were cultivated in De Man, Rogosa and Sharpe (MRS) broth, and different polyols (glycerol, mannitol, sorbitol, and xylitol) were added to the culture broth to stimulate the production of antifungal compounds. The fungal inhibition studies were performed using the poisoned food technique. The highest inhibition of A. carbonarius growth was obtained by cultivating L. plantarum MZ809351 in the presence of xylitol and glycerol. Under these conditions, 1 L of the L. plantarum MZ809351 cultures were used to identify antifungal compounds. The compounds were concentrated by solid-phase extraction and then characterized by GC-MS. In addition to 9-octadecenoic acid, 3 diketopiperazines or cyclic dipeptides were identified, including cyclo (Leu-Leu), cyclo (Pro-Gly) and cyclo (Val-Phe), which were compounds related to microbial antifungal activities. Xylitol and glycerol induced the production of these antifungal compounds against A. carbonarius Ac 162. On the other hand, adding xylitol and glycerol to the MRS broth reduced the Ochratoxin A (OTA) content to 56.8 and 54.7%, respectively. This study shows the potential for using L. plantarum MZ809351 as a biocontrol agent to prevent the growth of A. carbonarius and reduce the production of OTA in foods.

Development of a novel liquid crystal Apta-sensing platform using P-shape molecular switch

Described herein is a liquid crystal (LC)-based aptasensor via employing the reorientation of LC triggered by the conformational changes of a P-shaped DNA structure. The structure consists of a short linker sequence as an immobilizer probe with ability to hybridize with the central part of the intact aptamer (Apt) sequence and an Apt terminal-locker (ATL) strand with complementary segments of the Apt terminal fragments. Bindings of two arm segments of the Apt sequence with the ATL strand enforces it to form a P-shaped configuration on the sensing platform. The selective interaction between the Apt strand and OTA leads to the disassembly of the Apt-ATL hybrid, collapse of the P-shaped structure, and consequently, transition of the optical appearance of the aptasensor texture. Determination of Ochratoxin A (OTA) in foods is an urgent demand in attempt to minimize food safety risks. To demonstrate the feasibility of our aptasensing design, the OTA specific aptamer was selected as a model. The developed LC aptasensor possesses a wide linear range from 0.01 aM to 100 pM, ultra-low limit of detection (LOD) of 0.0078 aM, and quantitative recoveries of 91-103.51% for OTA in rice and grape juice samples. This study proposes a novel and universal LC-based platform for facile, ultra-sensitive, and precision sensing of hazardous analytes in real samples.

DNA Nanotechnology-Based Biosensors and Therapeutics

Over the past few decades, DNA nanotechnology engenders a vast variety of programmable nanostructures utilizing Watson-Crick base pairing. Due to their precise engineering, unprecedented programmability, and intrinsic biocompatibility, DNA nanostructures cannot only interact with small molecules, nucleic acids, proteins, viruses, and cancer cells, but also can serve as nanocarriers to deliver different therapeutic agents. Such addressability innate to DNA nanostructures enables their use in various fields of biomedical applications such as biosensors and cancer therapy. This review is begun with a brief introduction of the development of DNA nanotechnology, followed by a summary of recent applications of DNA nanostructures in biosensors and therapeutics. Finally, challenges and opportunities for practical applications of DNA nanotechnology are discussed.

Ochratoxins in Wines: A Review of Their Occurrence in the Last Decade, Toxicity, and Exposure Risk in Humans

Ochratoxins (OTs) are mycotoxins frequently found in wines, and their contamination can occur during any stage of the winemaking process. Ochratoxin A (OTA) has been the most widely reported and the only one whose concentrations are legislated in this beverage. However, ochratoxin B, ochratoxin A methyl ester, ochratoxin B methyl ester, ochratoxin A ethyl ester, ochratoxin B ethyl ester, ochratoxin α, ochratoxin β, OTα methyl ester, OTA ethyl amide, and OTA glucose ester have also been reported in wines. Thus, detecting only OTA would lead to the underestimation of ochratoxin levels, which is a risk to human health. Considering the threat represented by the presence of ochratoxins in wines and the long-term health problems that they can cause in wine drinkers, this paper aims to review reports of the last 10 years regarding the presence of different ochratoxins in wines and how the winemaking process influences the degree of contamination, mainly by OTA. Additionally, toxicity from human exposure due to the consumption of contaminated wines is addressed.

Enzyme cascade-amplified immunoassay based on the nanobody-alkaline phosphatase fusion and MnO2 nanosheets for the detection of ochratoxin A in coffee

Ochratoxin A (OTA) is a common food contaminant with multiple toxicities and thus rapid and accurate detection of OTA is indispensable to minimize the threat of OTA to public health. Herein a novel enzyme cascade-amplified immunoassay (ECAIA) based on the mutated nanobody-alkaline phosphatase fusion (mNb-AP) and MnO2 nanosheets was established for detecting OTA in coffee. The detection principle is that the dual functional mNb-AP could specifically recognize OTA and dephosphorylate the ascorbic acid-2-phosphate (AAP) into ascorbic acid (AA), and the MnO2 nanosheets mimicking the oxidase could be reduced by AA into Mn2+ and catalyze the 3,3',5,5'-tetramethyl benzidine into blue oxidized product for quantification. Using the optimal conditions, the ECAIA could be finished within 132.5 min and shows a limit of detection of 3.38 ng mL-1 (IC10) with an IC50 of 7.65 ng mL-1 and a linear range (IC20-IC80) of 4.55-12.85 ng mL-1. The ECAIA is highly selective for OTA. Good recovery rates (84.3-113%) with a relative standard deviation of 1.3-3% were obtained and confirmed by high performance liquid chromatography with a fluorescence detector. The developed ECAIA was demonstrated to be a useful tool for the detection of OTA in coffee which provides a reference for the analysis of other toxic small molecules.

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.

Functional Role of Aspergillus carbonariusAcOTAbZIP Gene, a bZIP Transcription Factor within the OTA Gene Cluster

Aspergillus carbonarius is the principal fungal species responsible for ochratoxin A (OTA) contamination of grapes and derived products in the main viticultural regions worldwide. In recent years, co-expressed genes representing a putative-OTA gene cluster were identified, and the deletion of a few of them allowed the partial elucidation of the biosynthetic pathway in the fungus. In the putative OTA-gene cluster is additionally present a bZIP transcription factor (AcOTAbZIP), and with this work, A. carbonarius ΔAcOTAbZIP strains were generated to study its functional role. According to phylogenetic analysis, the gene is conserved in the OTA-producing fungi. A Saccharomyces cerevisiae transcription factor binding motif (TFBM) homolog, associated with bZIP transcription factors was present in the A. carbonarius OTA-gene cluster no-coding regions. AcOTAbZIP deletion results in the loss of OTA and the intermediates OTB and OTβ. Additionally, in ΔAcOTAbZIP strains, a down-regulation of AcOTApks, AcOTAnrps, AcOTAp450, and AcOTAhal genes was observed compared to wild type (WT). These results provide evidence of the direct involvement of the AcOTAbZIP gene in the OTA biosynthetic pathway by regulating the involved genes. The loss of OTA biosynthesis ability does not affect fungal development as demonstrated by the comparison of ΔAcOTAbZIP strains and WT strains in terms of vegetative growth and asexual sporulation on three different media. Finally, no statistically significant differences in virulence were observed among ΔAcOTAbZIP strains and WT strains on artificially inoculated grape berries, demonstrating that OTA is not required by A. carbonarius for the pathogenicity process.

A signal amplification of p DNA@Ag2S based photoelectrochemical competitive sensor for the sensitive detection of OTA in microfluidic devices

In this work, a signal amplification competitive-type photoelectrochemical system comprised of bismuth sulfide/bismuth oxyiodide/zinc oxide (Bi₂S₃/BiOI/ZnO) nano-array as platform and Ag₂S-modified aptamers probe DNA (p DNA@Ag₂S) as competition content for rapid and sensitive detection of OTA in microfluidic devices. The BiOI nano-array was first growth on surfaces of ZnO by a simple electrodeposited method, which provided large specific surface area and high stability to solve distribution of sensing platform and loose of combination of sensing substrate. Then, the Bi₂S₃ could be in-situ growth by self-sacrificial part Bi³⁺ of BiOI to form heterojunction without destroying the structure of the nano-array. A strong photocurrent intensity was acquired by the Bi₂S₃/BiOI/ZnO modified onto indium tin oxide (ITO) electrode, due to its good matching cascade band-edge levels could improve efficient separation of photo-generated e^-/h⁺ pairs. After immobilizing with the capture DNA (c DNA) and the sequential hybridization of p DNA@Ag₂S, the photocurrent intensity reduced obviously because part photo-generated electron transformed to Ag₂S rather than Bi₂S₃/BiOI/ZnO electrode. Subsequently, the photocurrent intensity increased evident when immobilized the target OTA, owing to the OTA could bind the p DNA@Ag₂S to form the specific-complex that were released from the electrode surface. Under optimal conditions, the prepared PEC microfluidic sensor exhibited a linear concentration of OTA from 0.01 pg/mL to 200 ng/mL with a low detection limit of 0.0035 pg/mL (S/N = 3). Furthermore, it achieved high sensitivity, good specificity, and acceptable stability and further provided an efficient method for sensitive detection of other target mycotoxins in practical application.

Toxigenic fungal species and natural occurrence of mycotoxins in crops harvested in Argentina

Mycotoxins are secondary metabolites produced by fungal species that mainly belong to Aspergillus, Fusarium, Penicillium and Alternaria, which can grow in a variety of crops including cereals, oilseeds and fruits. Consequently, their prevalence in foods and by-products not only affects human and animal health but also causes important losses in both domestic and international markets. This review provides data about toxigenic fungal species and mycotoxin occurrence in different crops commonly grown in Argentina. This information will be relevant to establish adequate management strategies to reduce the impact of mycotoxins on human food and animal feed chains and to implement future legislation on the maximum permitted levels of these fungal metabolites.

Reducing Ochratoxin A Content in Grape Pomace by Different Methods

Grape pomace (GP) is the residue of grapes after wine making and is a valuable source of dietary polyphenol and fiber for health promotion. However, studies found the presence of ochratoxin A (OTA) in GP at very high concentrations, which raises a safety issue in the value-added utilization of GP. This study evaluated the effects of thermal pressure, baking, acid and enzymatic treatments on OTA content in GP. Thermal pressure treatment was conducted with wet GP at 121 °C for 10-30 min in an autoclave; acid treatments were conducted with hydrochloric acid, acetic acid, citric acid, and lactic acid, respectively, at 50 °C for 24 h. Baking was conducted using a cookie model. For enzymatic treatment, purified OTA solution was treated with carboxypeptidase A, alcalase, flavourzyme, pepsin, and lipase, respectively, and the effective enzymes were selected to treat GP. Results show that autoclaving for 10-30 min reduced 19-80% of OTA, varying with treatment time and GP variety. The effectiveness of acid treatment was similar to that of autoclaving and varied with acid type and GP variety. Baking increased the detectable OTA. Among all tested enzymes, carboxypeptidase A was the most effective in reducing OTA, followed by lipase and flavourzyme, but their effects were significantly lower in GP samples.

Antifungal efficacy of sanitizers and electrolyzed waters against toxigenic Aspergillus

The presence of mycotoxin-producing fungi in food production environments is a cause of concern since they can contaminate food products, synthesizing toxic compounds in later steps. To avoid this, an effective hygiene and sanitation process of the environment and equipment should be adopted, using sanitizing agents with adequate antifungal efficacy. This work evaluated the effectiveness of different chemical sanitizers: benzalkonium chloride (0.3%, 1.2%, 2%), biguanide (2%, 3.5%, 5%), iodine (0.2%, 0.6%, 1%), peracetic acid (0.3%, 0.6%, 1%), sodium hypochlorite (0.5%, 0.75%, 1%), besides a new non-polluting technology, the electrolyzed water, both the acid in the chlorine concentrations of 60, 85 and 121 ppm and the respective basic electrolyzed water formed against strains of toxigenic Aspergillus flavus, Aspergillus nomius, Aspergillus parasiticus, Aspergillus carbonarius, Aspergillus niger, Aspergillus ochraceus and Aspergillus westerdijkiae through the methodology recommended by the European Committee for Standardization. Benzalkonium chloride and iodine were the most effective sanitizers to eliminate Aspergillus from the Flavi and Nigri section. Peracetic acid showed the best elimination of the growth of Aspergillus from Circumdati section. Sodium hypochlorite, biguanide, and electrolyzed water agents were the least effective, reducing less than 3 log from initial control, not being the most suitable agents for the control of toxigenic fungi in food industries.

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.

Environmental-friendly gold nanoparticle immunochromatographic assay for ochratoxin A based on biosynthetic mimetic mycotoxin-conjugates

Ochratoxin A (OTA) is a possibly carcinogenic mycotoxin which is one of the most abundant food contaminants. It can be normally monitored and detected by immunochromatographic assays (ICG) which have a good sensitivity and specificity and easy to operate. However, the development of normal ICG is based on traditional OTA-conjugates or chemosynthetic mimotope peptides, which are very high-cost reagents with a detrimental effect on the environment and operators. This study takes advantage of both biosynthetic mimetic OTA-conjugates and a convenient IGG to develop a novel environmental-friendly and low-cost ICG for the rapid detection of OTA. Qualitatively, the visual cut-off level of the developed ICG for OTA was 0.8 ng/ml, which is 10-fold more sensitive than the chemosynthetic mimotope peptide based ICG, while there is no cross-reaction with other mycotoxins. The assay takes only 15 min to acquire results visible to the naked eye. Quantitatively, the half inhibition concentration of the ICG setup with mimetic OTA-conjugates was 0.187 ng/ml, with a linear range of 0.015 to 0.5 ng/ml. These results demonstrate the potential to adapt the method for detecting other toxic mycotoxins.

Biosynthetic Mycotoxin Conjugate Mimetics-Mediated Green Strategy for Multiplex Mycotoxin Immunochromatographic Assay

Various mycotoxins widely co-exist in agro-products, and their combined effects cause toxicity and potential carcinogenicity to humans and animals. In this work, we developed an economical and sensitive quantum dots (QDs)/QD microbead (QDs/QB)-based multiplex immunochromatographic assay (mICA) for the rapid detection of fumonisin B₁ (FB₁), zearalenone (ZEN), and ochratoxin A (OTA) without the building-up process of mycotoxin conjugates. QDs and QBs were selected as fluorescent reporters and conjugated with antimycotoxin monoclonal antibodies for improving sensitivity. Furthermore, phage-displayed FB₁, ZEN, and OTA mimotope peptide-based soluble and monovalent fusions to maltose-binding protein (MBP) were applied onto the test line of the mICA as the mimetic coating antigen. Under the optimized conditions, the visual detection limits (vLODs) of peptide-MBP-based mICA could be obtained as 0.25 ng/mL for FB₁, 3.0 ng/mL for ZEN, and 0.5 ng/mL for OTA within 10 min. The results for spiked real sample detection indicate good accuracy, reproducibility, and practicability. In addition, the proposed mICA was comparable with ultraperformance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS) in terms of reliability in detecting FB₁, ZEN, and OTA using natural samples. From the point of promoting commercial production, these time-saving and low-cost peptide-MBP antigens applied in ICA might provide promising potential for promoting productivity and decreasing the cost of production.

Nanobody-alkaline phosphatase fusion-mediated phosphate-triggered fluorescence immunoassay for ochratoxin a detection

Ochratoxin A (OTA) is a kind of mycotoxin that seriously harms the health of humans and animals. In this study, a nanobody-alkaline phosphatase fusion-mediated phosphate-triggered fluorescence immunoassay (Nb-AP-mediated PT-FIA) was developed for detecting OTA. Based on the constructed phosphate-triggered fluorescence sensing system for Nb-AP and the optimal working conditions, the Nb-AP-mediated PT-FIA has a half maximal inhibition concentration (IC₅₀) of 0.46 ng/mL, a limit of detection (IC₁₀) of 0.12 ng/mL, and a linear range (IC_20-80) of 0.2-1.26 ng/mL, respectively. The recovery experiment indicated acceptable accuracy and precision of the Nb-AP-mediated PT-FIA, and the results were validated by high performance liquid chromatography with fluorescence detector. Thus this proposed method is applicable to sensitive, rapid, and low-cost detection of OTA and other toxic analytes with low molecular weight in food and environment.

Antimicrobial Bacillus velezensis HC6: production of three kinds of lipopeptides and biocontrol potential in maize

AIMS

To study the antimicrobial agents of the Bacillus velezensis strain HC6 and assess the application potential of B. velezensis HC6 in maize.

METHODS AND RESULTS

We applied a dual culture technique to test the antimicrobial activity of B. velezensis HC6 against bacteria and fungi of common contaminated crops. Bacillus velezensis HC6 showed antagonistic action on pathogenic fungi, including Aspergillus and Fusarium, as well as pathogenic bacteria (especially Listeria monocytogenes). When applied in maize, B. velezensis HC6 could also inhibit the growth of multiple pathogenic fungi and reduce their production of aflatoxin and ochratoxin. Three kinds of antimicrobial lipopeptides, including iturin, fengycin and surfactin were identified in B. velezensis HC6 culture supernatant by high-performance liquid chromatography and MALDI-TOF mass spectrometry. Iturin and fengycin showed obvious antimicrobial activity to the tested fungal strains.

CONCLUSIONS

Bacillus velezensis HC6 produces three kinds of lipopeptides which showed antimicrobial activity against several common pathogenic fungi and bacteria. Bacillus velezensis HC6 is potential to be biocontrol bacteria in maize.

SIGNIFICANCE AND IMPACT OF THE STUDY

Bacillus velezensis HC6 shows obvious antimicrobial activity to important crops pathogenic fungi which usually produce mycotoxins that are harmful to animal and human health. We demonstrate that three different types of lipopeptides produced by B. velezensis contributed to the antimicrobial activity. Bacillus velezensis HC6 has the potential to be effective biocontrol agent in crops.

Occurence of Ochratoxin A and Biogenic Amines in Croatian Commercial Red Wines

Food safety is one of the main concerns in the world and in wine it depends mostly on metabolites of microbial origin. The aim of this study was to investigate the occurrence of natural contaminants, ochratoxin A and biogenic amines (cadaverine, histamine, putrescine and tyramine), in Croatian commercial red wines originating from different Croatian wine-making regions. Ochratoxin A was detected in 92.8% of samples, however its concentrations in all samples were more than 10-fold lower than the limit set by the European Union (2 µg/kg), marking these wines as safe for consumption. The frequency of occurrence and measured concentrations of ochratoxin A were higher in wines produced in southern regions with highest values obtained in wines from southern Dalmatian islands. All samples were contaminated with cadaverine and putrescine, while 88.2% and 82.7% were contaminated with histamine and tyramine, respectively. Histamine concentrations ranged from below the limit of detection to 8.5 mg/L. Higher histamine concentrations were measured in wines with higher pH values which coincided with southern geographic origin. These results reinforce the need for routine detection and quantification of biogenic amines in Croatian wines to achieve better control of vinification and minimize their formation.

Intraspecific variability of growth and ochratoxin A production by Aspergillus carbonarius from different foods and geographical areas

Ochratoxin A (OTA) is a nephrotoxic mycotoxin naturally found in a wide range of food commodities throughout the world. Aspergillus carbonarius is the most important source of OTA in food commodities such as wine, grapes and dried vine fruits and is also responsible for the formation of OTA in coffee. The aim of this study was to determine the simultaneous effect of three culture media (Czapek Yeast Extract Broth (CYB); Synthetic Grape Juice Medium (SGM) and White grape juice (WGJ)) at three water activity (a_w) levels (0.90; 0.95 and 0.98-0.99), and three incubation temperatures (15 °C, 25 °C and 35 °C) on the growth and OTA production by 16 strains of A. carbonarius. The strains were mainly isolated from grapes from areas with a Mediterranean climate. All the strains were confirmed for identity by sequencing of the calmodulin gene. The assay was performed in microtiter plates, determining the absorbance at 530 nm and the concentration of OTA after 1, 2, 4 and 10 days of incubation. No significant differences were observed in absorbance values between the strains. The highest absorbance values were recorded in CYB at 0.99 a_w and at 0.95 a_w after 10 days of incubation at 25 °C and 35 °C. None of the strains were able to grow at 0.90 a_w and 15 °C in any culture media after 10 days of incubation. OTA concentration was statistically higher at 15 °C than at 25 °C or 35 °C. The highest significant OTA values were obtained at 0.98-0.99 a_w and the best culture media for OTA production was CYB, followed by WGJ and SGM. While strains isolated from Mediterranean climate foods had a similar behavior despite being isolated from different geographical areas, OTA concentration produced by one Robusta coffee strain from Thailand was statistically higher at 25 °C than at 15 °C. This would suggest that the type of food matrices and consequently the adaptation of A. carbonarius strains to different climatic conditions would have a greater influence on the ecophysiology of the strains than only their geographical origin.

A simple and sensitive electrochemiluminescence aptasensor for determination of ochratoxin A based on a nicking endonuclease-powered DNA walking machine

Ochratoxin A (OTA) poses a serious threat to the health of human beings and animals. In this paper, a simple and sensitive electrochemiluminescence (ECL) aptasensor was constructed to detect OTA based on electrochemiluminescence resonance energy transfer (ECL-RET) and a nicking endonuclease-powered DNA walking machine. Originally, the signal of cadmium sulfide semiconductor quantum dots (CdS QDs) was quenched efficiently by Cy5. After the addition of OTA, the walker autonomously hybridized with Cy5-labeled DNA and released plenty of Cy5-DNA from the electrode surface with the help of a nicking endonuclease. As a result, the signal of CdS QDs recovered efficiently. As an artificial and popular signal amplification technique, the DNA walking machine greatly improved the sensitivity. Under optimal conditions, the aptasensor not only detected OTA in a linear range from 0.05 nM to 5 nM with a detection limit of 0.012 nM (S/N = 3), but also showed an excellent selectivity for OTA over other mycotoxins.