Ochratoxin – Characteristics, influences and challenges of global research

Mechanisms of action of bioprotective plant extracts against the ochratoxigenic Penicillium nordicum in dry-cured sausages

Plant extracts are promising strategies to minimise the hazard associated with ochratoxin A (OTA) in dry-cured sausages. Nonetheless, their mechanisms have not been elucidated yet. The mechanisms by which rosemary (REO), thyme (TEO) and oregano (OEO) essential oils and the extract of acorn shell (AE) impact on the OTA production by Penicillium nordicum were evaluated. Their effect on the mould's gene expression, ergosterol synthesis, reactive oxygen species (ROS) production and spore germination and their potential to the OTA detoxification were in vitro studied in three mould strains. Differences at sampling time, plant extract and mould strain levels were found for all mechanisms of the antifungal agents. The relative expression of Hog1 and Rho1 genes were less affected than that of the otanps and otapks genes in treated moulds compared to the non-treated control. All treatments were able to decrease ergosterol production against one strain. Furthermore, REO 500 μL/mL, AE and OEO 50 μL/mL produced the highest fluorescence associated with ROS for another strain at the end of the incubation. Moreover, a significant detoxification of the plant extracts was only found for OEO 50 μL/mL after 24 h of incubation. Besides, spore germination was totally inhibited by TEO and OEO, obtaining the opposite effect for AE. No clear relationship was found when those findings were correlated to the OTA accumulation. Consequently, the antiochratoxigenic effect of plant extracts seems to be due to the involvement of several mechanisms of action. Finally, the plant extracts did not inhibit the potentially protective cultures against ochratoxigenic moulds.

Label-free localized surface plasmon resonance (LSPR) biosensor, based on Au-Ag NPs embedded in TiO2 matrix, for detection of Ochratoxin-A (OTA) in wine

Ochratoxin-A (OTA) is a widespread foodstuff contaminant with potential carcinogenic effects. Innovative sensing technologies that allow on-site and sensitive food screening can have a significant impact on food and environment safety. A novel and quantitative label-free LSPR-based biosensor was specifically designed for OTA detection, employing a portable LSPR spectroscopy sensing system for efficient on-site and cost-effective analysis. This biosensor is comprised of monoclonal anti-OTA antibodies immobilized on the surface of sputtered Au-Ag nanoparticles embedded in a TiO2 matrix. Under optimized conditions, the LSPR-based biosensor demonstrated a linear dynamic response from 0.05 to 2 ng mL-1, with an estimated limit of detection at 7 pg mL-1, using 55 μL of sample, outperforming commercial ELISA technique in relevant bioanalytical parameters. Sensitivity in OTA detection is crucial because it ensures the accurate identification of low concentrations, which is essential for preventing health risks associated to cumulative ingestion of contaminated food products. The robustness and feasibility of the presented LSPR-based biosensing was tested using spiked white wine, exhibiting a satisfactory recovery of 93 %-113 %, confirming its efficacy in a complex matrix.

Untargeted metabolomics to relate changes produced by biocontrol agents against Aspergillus westerdijkiae and Penicillium nordicum in vitro on dry-cured ham

Dry-cured ham is a highly appreciated meat product. During the ripening, moulds grow on its surface such as Penicillium nordicum and Aspergillus westerdijkiae producers of ochratoxin A (OTA). This mycotoxin poses a risk to consumers that must be controlled. The aim of this work is to evaluate the effectiveness of Debaryomyces hansenii and Staphylococcus xylosus isolated from dry-cured ham as a combined biocontrol culture (BCA) to reduce the OTA produced by one strain of A. westerdijkiae and two strain of P. nordicum, and to assess the metabolomic changes they cause. Each mould was inoculated alone and in combination with BCA on dry-cured ham for 14 days at 20 °C. OTA and total metabolites were analysed in a mass spectrometer Orbitrap Q- Exactive Plus. The Compound Discoverer software, in-house Python-based software and the Metaboanalyst software were used for metabolite analysis. BCA reduced the OTA of A. westerdijkiae, P. nordicum 15 and P. nordicum 856 by 78 %, 99 % and 65 % respectively. BCA caused changes in their metabolome, mainly in the phenylalanine metabolism pathway altering compounds such as Phenylacetaldehyde, Phenylpyruvate or trans-2-hydroxycinnamate, the synthesis of phenylalanine, tyrosine, and tryptophan altering compounds such as 4-hydroxyphenylpyruvate or L-tryptophan, and in the synthesis of oxylipins derived from the linoleic acid metabolism such as 13-OxoODE, 9(S)-HODE or 9(10)-EpOME.

Quercetin protects the liver of broiler chicken against oxidative stress and apoptosis induced by ochratoxin A

Ochratoxin A (OTA) is a mycotoxin that causes major health concerns in human and animals. Quercetin (QUE) is a flavonoid that possesses antioxidant, anti-inflammatory and anti-apoptotic properties. This report aims to investigate the ameliorative effects of QUE against OTA-induced hepatotoxicity in broiler chicken. Forty broiler chicks were equally allocated into 4 groups: Group I (control), Group II (OTA), Group III (QUE) and Group IV (OTA + QUE). OTA (0.5 mg/kg) and QUE (0.5 g/kg) were incorporated into the chicken feed for 42 days. The results presented a significant decrease in body weight and elevation in feed conversion ratio, and a significant elevation of the activities of serum alanine aminotransferase and aspartate aminotransferase enzymes in the OTA birds. Additionally, there was a significant decrease in catalase activity and reduced glutathione content and a significant elevation in malondialdehyde level in the liver of OTA-exposed birds. Various hepatocellular lesions were also noticed in the OTA-exposed birds. OTA exposure up-regulated the phosphatase and tensin homologue (PTEN) and the pro-apoptotic genes and down-regulated the anti-apoptotic genes in the liver. The addition of QUE ameliorated most of the hepatotoxic effects of OTA.

Application of Anti-Immune Complex Reagents in Small Molecule Analyte Immunoassays

The detection of small molecule analytes (SMAs) is of great significance for food and drug testing, environmental monitoring, and disease diagnosis. However, the performance of commercially available SMA immunoassays is limited by their low sensitivity and specificity due to the competitive format, leaving significant room for improvement. In recent years, the application of noncompetitive immunoassays for the detection of SMAs has become a hot topic, especially with the rapid evolution of antibody development technology. The remarkable development and application of anti-immune complex (anti-IC) reagents targeting antigen-specific antibodies have garnered significant interest from researchers and diagnostic companies, particularly in the field of SMA detection. The discovery and development history of anti-IC antibodies, the advantages and limitations of different anti-IC reagent preparation methods, and the mechanisms of interaction between ICs and anti-IC antibodies are reviewed. A comprehensive overview of the application of anti-IC antibodies in SMAs assay, including pesticide residue detection, mycotoxin detection, and clinical testing, as well as current challenges and potential solutions in noncompetitive immunoassays, is also summarized to provide a reference for the rapid and accurate detection of SMAs.

Detection of foodborne pathogens in contaminated food using nanomaterial-based electrochemical biosensors

Foodborne pathogens are a grave concern for the for food, medical, environmental, and economic sectors. Their ease of transmission and resistance to treatments, such as antimicrobial agents, make them an important challenge. Food tainted with these pathogens is swiftly rejected, and if ingested, can result in severe illnesses and even fatalities. This review provides and overview of the current status of various pathogens and their metabolites transmitted through food. Despite a plethora of studies on treatments to eradicate and inhibit these pathogens, their indiscriminate use can compromise the sensory properties of food and lead to contamination. Therefore, the study of detection methods such as electrochemical biosensors has been proposed, which are devices with advantages such as simplicity, fast response, and sensitivity. However, these biosensors may also present some limitations. In this regard, it has been reported that nanomaterials with high conductivity, surface-to-volume ratio, and robustness have been observed to improve the detection of foodborne pathogens or their metabolites. Therefore, in this work, we analyze the detection of pathogens transmitted through food and their metabolites using electrochemical biosensors based on nanomaterials.

Deciphering Staphylococcus xylosus and Staphylococcus equorum mode of action against Penicillium nordicum in a dry-cured ham model system

Penicillium nordicum is one of the major producers of ochratoxin A (OTA) in dry-cured ham. Staphylococcus xylosus Sx8 and Staphylococcus equorum Se31 have been previously proposed as biocontrol agents (BCAs) to prevent the OTA contamination, although their antifungal mode of action has not been established yet. Thus, the aim of this work was to elucidate their mode of action against P. nordicum in a dry-cured ham model system. For this, the effect of live cells, dead cells, and cell-free broth; the nutritional utilisation pattern, niche overlap index (NOI), interactions by dual-culture assays, antifungal effect of volatile compounds, OTA detoxification, and effect on fungal proteome were determined. No fungal growth was observed after 14 days of co-culture with live cells of each staphylococcus at 15 or 20 °C. However, such inhibition was not observed with either dead cells or extracellular extracts. The number of carbon sources utilised by P. nordicum was higher than those used by both cocci at 20 °C, whilst the opposite occurred at 15 °C. According to NOI, nutritional dominance depends on temperature, at 20 °C P. nordicum dominated the niche, but at 15 °C the mould is dominated by the BCAs. The volatile pattern generated by each coccus did not show antifungal effect, and both staphylococci failed to degrade or adsorb OTA. However, in the interaction assay, S. xylosus and S. equorum were able to decrease the fungal growth and its OTA production. In addition, proteomic analyses showed changes in the abundance of proteins related to the cell wall integrity (CWI), carbohydrate metabolism and the biosynthesis of secondary metabolites such as OTA. In conclusion, overall, the antagonistic effects of the two studied cocci against P. nordicum are greater at 15 °C than at 20 °C, being linked to competition for space and nutrients, triggering alterations in CWI pathway, OTA biosynthesis, and carbohydrate metabolism.

Effects of Aspergillus niger Infection on the Quality of Jujube and Ochratoxin A Cumulative Effect

The jujube is one of the most popular fruits in China because of its delicious taste and high nutritional value. It has a long history of usage as an important food or traditional medicine. However, the jujube is easily infected by fungi, which causes economic losses and threatens human health. When the jujube was infected by Aspergillus niger (H1), the changes in nutritional qualities were determined, such as the content of total acid, vitamin C, reducing sugar, etc. In addition, the ability of A. niger (H1) to produce ochratoxin A (OTA) in different inoculation times and culture media was evaluated, and the content of OTA in jujubes was also analyzed. After jujubes were infected by A. niger (H1), the total acid, and vitamin C contents increased, while the total phenol content decreased, and the reducing sugar content increased after an initial decrease. Although A. niger (H1) infection caused the jujubes to rot and affected its quality, OTA had not been detected. This research provides a theoretical foundation for maximizing edible safety and evaluating the losses caused by fungal disease in jujubes.

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.

Public health risk associated with the co-occurrence of aflatoxin B1 and ochratoxin A in spices, herbs, and nuts in Lebanon

Background

Aflatoxin B1 and ochratoxin A are mycotoxins produced by filamentous fungi that attack crops on field and storage. Both mycotoxins present a risk on public health since aflatoxin B1 is a hepatotoxic and hepatocarcinogenic agent while ochratoxin A can be nephrotoxic. Those mycotoxins can be found in several food items including spices, herbs, and nuts.

Objectives

In Lebanon, few studies address aflatoxin B1 and ochratoxin A contamination in spices, herbs, and nuts. So, the aim of this study is to investigate the concentrations of those two mycotoxins particularly in spices and herbs and the concentration of aflatoxin B1 in nuts, and to determine the dietary exposure of the Lebanese population and their possible attribution to liver cancer and renal damage.

Methods

In this work, a total of 198 samples of spices, herbs, and nuts were collected from different sites. Aflatoxin B1 and ochratoxin A were quantified using immune-affinity columns. A food frequency questionnaire was used to quantify the consumption of spices, herbs, and nuts in Lebanon. Exposure to aflatoxin B1 and ochratoxin A was calculated accordingly and liver and kidney cancer risks were evaluated.

Results

Aflatoxin B1 was respectively found in 100, 20.4, and 98.6% of the spices, herbs, and nuts samples, while ochratoxin A was found in 100 and 44.4% of spices and herbs, respectively. Aflatoxin B1 was found at mean concentration of 0.97, 0.27, and 0.40 μg/kg in spices, herbs, and nuts, respectively while ochratoxin A was found at mean concentrations of 38.8 and 1.81 μg/kg in spices and herbs, respectively. Aflatoxin B1 occurrence was shown to be associated in this study with 0.017 additional cancer cases per 100,000 persons per year, and ochratoxin A weekly exposure was shown to be 5.04 ng/kg bw less than the Provisional Tolerable Weekly Intake of 100 ng/kg bw which indicates low risk of renal damage from spices and herbs consumption.

Conclusion

The consumption of spices, herbs, and nuts in Lebanon could lead to an increase in health risks associated with aflatoxin B1 and ochratoxin A, specifically spices. The reported occurrence may be directly related to poor storage conditions.

Nanobody/NanoBiT system-mediated bioluminescence immunosensor for one-step homogeneous detection of trace ochratoxin A in food

Hazardous small molecules in food and environment seriously threatens human health, which requires sensitive and rapid tools for monitoring. Using a previously identified nanobody against ochratoxin A (OTA), we herein proposed a homogeneous sensing platform "nanobody/NanoLuc Binary Technology (NanoBiT) system" and developed a nanobody/NanoBiT system-mediated bioluminescence immunosensor (NBL-Immunosens) for OTA using LgBiT (Lg) and SmBiT (Sm), two subunits of the split nanoluciferase (NanoLuc). The core elements of NBL-Immunosens include Lg-nanobody fusion (NLg) and Sm-labeled OTA-bovine serum albumin conjugate (OSm). The antigen-antibody interaction between NLg and OSm triggers the reconstitution of NanoLuc for generating luminescence signals. Moreover, free OTA can compete with OSm for binding to NLg, resulting the decrease of dose-dependent signals. NBL-Immunosens can detect OTA in a one-step assay of 5 min without washing and exhibit a limit of detection of 0.01 ng/mL with a linear range of 0.04-2.23 ng/mL. It shows high selectivity for OTA and has good accuracy and precision in the spiking-and-recovery experiments. Furthermore, its effectiveness was evaluated with real cereal samples and confirmed by liquid chromatography tandem mass spectrometry and commercial ELISA kits. Hence, the NBL-Immunosens is a very promising tool for rapid, accurate, and selective detection of trace OTA in food.

Development of a graphene oxide nanosheet and double-stranded DNA structure based fluorescent "signal off" aptasensor for ochratoxin A detection in malt

A "signal off" fluorescent aptasensor based on graphene oxide (GO) nanosheet and double-stranded DNA structure was fabricated for OTA detection. In the absence of OTA, the aptamer and its complementary DNA (cDNA) formed double-stranded conjugates that could coexist with GO, presenting fluorescence responses. Then, the presented OTA was captured by the aptamers, causing the release of cDNA-FAM probes. The free probes were adsorbed by GO, leading to an OTA concentration-dependent fluorescence quenching through fluorescence resonance energy transfer. Under optimum conditions, the fluorescent aptasensor exhibited outstanding sensitivity with a LOD of 11 pg/mL and a wide dynamic range of 0.04-30 ng/mL. The selectivity of the aptasensor was confirmed against other four mycotoxins, and the feasibility and reliability were verified by determining OTA in the spiked malt samples with satisfactory recovery of 95.50%-112.05%. This aptasensing platform could be adapted to measure other mycotoxins by replacing the aptamer sequences for food safety.

Exposure and risk characterizations of ochratoxins A and aflatoxins through maize (Zea mays) consumed in different agro-ecological zones of Ghana

Mycotoxin contamination of foodstuffs is a serious food safety concern globally as the prolonged ingestion of these toxins has the tendency to worsen the risk of hepatocellular carcinoma. This study aimed at estimating ochratoxin A (OTA) and aflatoxin (AF) levels above international (European Food Safety Authority, EFSA) and local (Ghana Standards Authority, GSA) standards as well as the health risks associated with the consumption of maize (n = 180) sampled from six (6) regions representing the agro-ecological zones of Ghana. OTA and AF were measured with High-Performance Liquid Chromatography with a Fluorescence detector. Out of the 180 samples analyzed for total aflatoxins (AFtotal), 131/180 tested positive and 127 (70.50%) exceeded the limits of EFSA and ranged 4.27-441.02 µg/kg. While for GSA, 116 (64.44%) of samples exceeded this limit and ranged between 10.18 and 441.02 µg/kg. For OTA, 103/180 tested positive and 94 (52.22%) of samples between the range 4.00-97.51 µg/kg exceeded the tolerable limit of EFSA, whereas 89 (49.44%) and were in the range of 3.30-97.51 µg/kg exceeded the limits of GSA. Risk assessment values for total aflatoxins (AFtotal) ranged between 50 and 1150 ng/kg bw/day, 0.4-6.67, 0-0.0323 aflatoxins ng/kg bw/day and 1.62-37.15 cases/100,000 person/year for Estimated Daily Intake (EDI), Margin of Exposure (MOE), Average Potency, and Cancer Risks respectively. Likewise, ochratoxin (OTA) values were in the ranges of 8.6 × 10-3-450 ng/kg bw/day, 0.05-2059.97, 0-0.0323 ochratoxins ng/kg bw/day and 2.78 × 10-4-14.54 cases/100,000 person/year. Consumption of maize posed adverse health effects in all age categories of the locations studied since the calculated MOE values were less than 10,000.

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.

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.