Reduction of ochratoxin A during the fermentation of Italian red wine Moscato

Practical Strategies to Reduce Ochratoxin A in Foods

Ochratoxin A (OTA), a potent nephrotoxin, is one of the most deleterious mycotoxins, with its prevalence in agricultural crops and their processed foods around the world. OTA is a major concern to food safety, as OTA exposure through dietary intake may lead to a significant level of accumulation in the body as a result of its long half-life (about 35 days). Its potent renal toxicity and high risk of exposure as well as the difficulty in controlling environmental factors OTA production has prompted the need for timely information on practical strategies for the food industry to effectively manage OTA contamination during food processing. The effects of various food processes, including both nonthermal and thermal methods, on the reduction in OTA were summarized in this review, with emphasis on the toxicity of residual OTA as well as its known and unknown degradation products. Since complete removal of OTA from foodstuffs is not feasible, additional strategies that may facilitate the reduction in OTA in food, such as adding baking soda and sugars, was also discussed, so that the industry may understand and apply practical measures to ensure the safety of its products destined for human consumption.

Obtaining an aflatoxin-free and high-alcohol-content product using contaminated dried figs

Dried fig is one of the most susceptible products to aflatoxin contamination. Since contaminated figs are not suitable for human consumption and cannot be used for any other purposes, they are burned in a chemical incinerator. In this study, we investigated the potential of using aflatoxin-contaminated dried figs as a raw material for ethanol production. For this purpose, contaminated dried figs (and also uncontaminated controls) were subjected to fermentation and subsequent distillation, and the alcohol and aflatoxin levels were determined during the processes. In addition, volatile by-products in the final product were determined using gas chromatography. Contaminated and uncontaminated figs had similar fermentation and distillation patterns. Although fermentation caused significant decreases in aflatoxin levels, there were still toxin residues in the fermented samples at the end of the process. On the other hand, aflatoxins were completely removed in the first step of the distillation. There were minor differences between the volatile compound compositions of the distillates produced from contaminated and uncontaminated figs. It was shown that obtaining aflatoxin-free and high-alcohol-content product using contaminated dried figs is possible according to the lab-scale conducted studies. Aflatoxin-contaminated dried figs can be used as a sustainable raw material for producing ethyl alcohol that can be used as an ingredient of surface disinfectants and/or fuel additive for vehicles.

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.

Monitoring of mycotoxins and pesticides in winemaking

This study monitored concentrations of both pesticides 2,4-dichlorophenoxyacetic acid (2,4-D) and procymidone, and mycotoxin ochratoxin A (OTA) in stages of the winemaking process. Sampling was carried out in the usual vinification process of red wine in a winery between the steps to obtain must and alcoholic fermentation. The highest transference of contaminants in the process occurred in the crushing step to 2,4-D (100%) and maceration to OTA and procymidone (100%). Removal of contaminants in the winemaking process corresponded to 100%, with a half-life (T1/2) longer for procymidone (216.5 h) and shorter for 2,4-D (38.5 h) and OTA (96 h). The processing factors (PFs) (0) for the contaminants, together with the data obtained, characterize winemaking as a process of reducing mycotoxin and pesticides. Results highlight the importance of fermentation to reduce contaminants and that yeasts promote detoxification

Diversity of Mycobiota in Spanish Grape Berries and Selection of Hanseniaspora uvarum U1 to Prevent Mycotoxin Contamination

The occurrence of mycotoxins on grapes poses a high risk for food safety; thus, it is necessary to implement effective prevention methods. In this work, a metagenomic approach revealed the presence of important mycotoxigenic fungi in grape berries, including Aspergillus flavus, Aspergillus niger aggregate species, or Aspergillus section Circumdati. However, A. carbonarius was not detected in any sample. One of the samples was not contaminated by any mycotoxigenic species, and, therefore, it was selected for the isolation of potential biocontrol agents. In this context, Hanseniaspora uvarum U1 was selected for biocontrol in vitro assays. The results showed that this yeast is able to reduce the growth rate of the main ochratoxigenic and aflatoxigenic Aspergillus spp. occurring on grapes. Moreover, H. uvarum U1 seems to be an effective detoxifying agent for aflatoxin B₁ and ochratoxin A, probably mediated by the mechanisms of adsorption to the cell wall and other active mechanisms. Therefore, H. uvarum U1 should be considered in an integrated approach to preventing AFB₁ and OTA in grapes due to its potential as a biocontrol and detoxifying agent.

Proteomic profiling and glycomic analysis of the yeast cell wall in strains with Aflatoxin B1 elimination ability

The use of microorganisms for Aflatoxin B₁ elimination has been studied as a new alternative tool and it is known that cell wall carried out a critical role. For that reason, cell wall and soluble intracellular fraction of eight yeasts with AFB₁ detoxification capability were analysed. The quantitative and qualitative comparative label-free proteomic allowed the identification of diverse common constituent proteins, which revealed that putative cell wall proteins entailed less than 10% of the total proteome. It was possible to characterize different enzymes linked to cell wall polysaccharides biosynthesis as well as other proteins related with the cell wall organization and regulation. Additionally, the concentration of the principal polysaccharides was determined which permitted us to observe that β-glucans concentration was higher than mannans in most of the samples. In order to better understand the biosorption role of the cell wall against the AFB₁ , an antimycotic (Caspofungin) was used to damage the cell wall structure. This assay allowed the observation of an effect on the normal growth of those yeasts with damaged cell walls that were exposed to AFB₁ . This effect was not observed in yeast with intact cell walls, which may reveal a protective role of this structure against mycotoxins.

Selection of Wine Saccharomyces cerevisiae Strains and Their Screening for the Adsorption Activity of Pigments, Phenolics and Ochratoxin A

Ochratoxin A is a dangerous mycotoxin present in wines and is considered the principal safety hazard in the winemaking process. Several authors have investigated the ochratoxin A adsorption ability of Saccharomyces cerevisiae yeasts, and specifically selected strains for this desired trait. In the present work, a huge selection of wine yeasts was done starting from Portuguese, Spanish and Italian fermenting musts of different cultivars. Firstly, 150 isolates were collected, and 99 non-redundant S. cerevisiae strains were identified. Then, the strains were screened following a multi-step approach in order to select those having primary oenological traits, mainly (a) good fermentation performance, (b) low production of H2S and (c) low production of acetic acid. The preselected strains were further investigated for their adsorption activity of pigments, phenolic compounds and ochratoxin A. Finally, 10 strains showed the desired features. The goal of this work was to select the strains capable of absorbing ochratoxin A but not pigments and phenolic compounds in order to improve and valorise both the quality and safety of red wines. The selected strains are considered good candidates for wine starters, moreover, they can be exploited to obtain a further enhancement of the specific adsorption/non-adsorption activity by applying a yeast breeding approach.

Detoxification of Ochratoxin A by a novel Aspergillus oryzae strain and optimization of its biodegradation

The mycotoxin Ochratoxin A (OTA) causes serious health risks and is found in food products throughout the world. The most promising method to detoxify this compound is biodegradation. In this study, Aspergillus oryzae strain M30011 was isolated and characterized based on its considerable capacity to degrade OTA. The degradation product (compound I) of A. oryzae-treated OTA was isolated, and its toxicity response was also evaluated. Furthermore, the relationships between three key cultivation condition factors affecting the OTA degradation rate were examined using the response surface methodology (RSM). Compound I was identified as ochratoxin α (C₁₁H₉O₅Cl), and the toxicity response experiments indicated that A. oryzae detoxified OTA to a great extent. A maximum degradation rate of 94% was observed after 72h. This study demonstrates the potential for using A. oryzae to detoxify OTA and suggests that it could be applied in the food industry to improve food safety and quality.

The Influence of Non-Saccharomyces Species on Wine Fermentation Quality Parameters

In the past, some microbiological studies have considered most non-Saccharomyces species to be undesirable spoilage microorganisms. For several decades, that belief made the Saccharomyces genus the only option considered by winemakers for achieving the best possible wine quality. Nevertheless, in recent decades, some strains of non-Saccharomyces species have been proven to improve the quality of wine. Non-Saccharomyces species can positively influence quality parameters such as aroma, acidity, color, and food safety. These quality improvements allow winemakers to produce innovative and differentiated wines. For that reason, the yeast strains Torulaspora delbrueckii, Lachancea thermotolerans, Metschnikowia pulcherrima, Schizosaccharomyces pombe, and Pichia kluyveri are now available on the market. Other interesting species, such as Starmerella bacillaris, Meyerozyma guilliermondii, Hanseniospora spp., and others, will probably be available in the near future.

Degrading Ochratoxin A and Zearalenone Mycotoxins Using a Multifunctional Recombinant Enzyme

Zearalenone (ZEA) is an estrogenic and ochratoxin A (OTA) is a hepatotoxic Fusarium mycotoxin commonly seen in cereals and fruits products. No previous investigation has studied on a single platform for the multi degradation mycotoxin. The current study aimed to investigate the bifunctional activity of a novel fusion recombinant. We have generated a recombinant fusion enzyme (ZHDCP) by combining two single genes named zearalenone hydrolase (ZHD) and carboxypeptidase (CP) in frame deletion by crossover polymerase chain reaction (PCR). We identified enzymatic properties and cell cytotoxicity assay of ZHDCP enzyme. Our findings have demonstrated that ZEA was completely degraded to the non-toxic product in 2 h by ZHDCP enzyme at an optimum pH of 7 and a temperature of 35 °C. For the first time, it was found out that ZEA 60% was degraded by CP degrades in 48 h. Fusion ZHDCP and CP enzyme were able to degrade 100% OTA in 30 min at pH 7 and temperature 30 °C. ZEA- and OTA-induced cell death and increased cell apoptosis rate and regulated mRNA expression of Sirt1, Bax, Bcl2, Caspase3, TNFα, and IL6 genes. Our novel findings demonstrated that the fusion enzyme ZHDCP possess bifunctional activity (degrade OTA and ZEA), and it could be used to degrade more mycotoxins.

The Management of Compounds that Influence Human Health in Modern Winemaking from an HACCP Point of View

The undesirable effects of some hazardous compounds involved in the different steps of the winemaking process may pose health risks to consumers; hence, the importance of compliance with recent international food safety standards, including the Hazard Analysis and Critical Control Point (HACCP) standards. In recent years, there has been a rise in the development of new technologies in response to the hazardous effects of chemical compounds detected during the winemaking process, whether naturally produced or added during different winemaking processes. The main purpose was to reduce the levels of some compounds, such as biogenic amines, ethyl carbamate, ochratoxin A, and sulfur dioxide. These technological advances are currently considered a necessity, because they produce wines free of health-hazardous compounds and, most importantly, help in the management and prevention of health risks. This review shows how to prevent and control the most common potential health risks of wine using a HACCP methodology.

Reduction of Mycotoxins during Fermentation of Whole Grain Sorghum to Whole Grain Ting (a Southern African Food)

Mycotoxins are fungal secondary metabolites that pose health risks to exposed individuals, requiring necessary measures to reduce them. Using liquid chromatography-tandem mass spectrometry (LC-MS/MS), mycotoxins were quantified in whole grain sorghum and ting subsequently derived from two sorghum varieties (high and low tannin). The whole grain (WG) ting samples were obtained by fermenting sorghum with Lactobacillus fermentum strains (FUA 3165 and FUA 3321). Naturally (spontaneously) fermented WG-ting under the same conditions were equally analysed. Among the mycotoxins investigated, fumonisin B₁ (FB₁), B₂ (FB₂), B₃ (FB₃), T-2 toxin (T-2), zearalenone (ZEA), alpha-zearalenol (α-ZOL) and beta-zearalenol (β-ZOL) were detected in sorghum. Results obtained showed that mycotoxin concentrations significantly (p ≤ 0.05) reduced after fermentation. In particular, L. fermentum FUA 3321 showed the capability to significantly (p ≤ 0.05) reduce all the mycotoxins by 98% for FB₁, 84% for T-2 and up to 82% for α-ZOL, compared to raw low tannin sorghum. Fermenting with the L. fermentum strains showed potential to effectively reduce mycotoxin contamination in whole grain ting. Thus, we recommended L. fermentum FUA 3321 in particular to be used as a potential starter culture in sorghum fermentation.

Development of an Antifungal and Antimycotoxigenic Device Containing Allyl Isothiocyanate for Silo Fumigation

The aims of this study were to evaluate the antifungal activity of the bioactive compound allyl isothiocyanate (AITC) against Aspergillus flavus (8111 ISPA) aflatoxins (AFs) producer and Penicillium verrucosum (D-01847 VTT) ochratoxin A (OTA) producer on corn, barley, and wheat. The experiments were carried out initially in a simulated silo system for laboratory scale composed of glass jars (1 L). Barley and wheat were contaminated with P. verrucosum and corn with A. flavus. The cereals were treated with a hydroxyethylcellulose gel disk to which 500 µL/L of AITC were added; the silo system was closed and incubated for 30 days at 21 °C. After that, simulated silos of 100 L capacity were used. Barley, wheat, and corn were contaminated under the same conditions as the previous trial and treated with disks with 5 mL of AITC, closed and incubated for 90 days at 21 °C. In both cases, the control test did not receive any antifungal treatment. The growth of the inoculated fungi and the reduction in the formation of AFs and OTA were determined. In the lab scale silo system, complete inhibition of fungal growth at 30 days has been observed. In corn, the reduction of aflatoxin B1 (AFB₁) was 98.5%. In the 100 L plastic drums, a significant reduction in the growth of A. flavus was observed, as well as the OTA formation in wheat (99.5%) and barley (92.0%).

Mycobiota and co-occurrence of mycotoxins in South African maize-based opaque beer

Beer, a beverage consumed throughout the world, is mainly derived from cereals. In this study, fungal and mycotoxin contamination, as well as the physicochemical properties of maize-based opaque beer (umqombothi) obtained from the Gauteng province of South Africa, was investigated. The mean water activity, pH and total titratable acidity of the analysed beer samples were 0.91, 3.76 and 1.20% lactic acid, respectively. The investigation revealed Aspergillus, Penicillium, Phoma and Saccharomyces as the predominant fungal genera with a mean fungal load of 3.66 × 10⁵ CFU/mL. Among the mycotoxigenic fungal species recovered, Aspergillus flavus had the highest incidence of 26%. Previously unreported strains such as P. chrysogenum strain AD25, A. sydowii strain AD 22 and A. tritici strain AD 11 were found. Furthermore, mycotoxin quantitative analysis via liquid chromatography-tandem mass spectrophotometry showed that deoxynivalenol was the dominant mycotoxin occurring in 84% of the samples. This was followed by enniatin B that occurred in 75% of samples ranging from 12 to 44 μg/L and fumonisin B₁ (FB₁) (incidence of 53% at a maximum level of 182 μg/L). Generally, there was low occurrence aflatoxins, whereas T-2, HT-2, nivalenol, zearalenone, 3- and 15-acetyl-deoxynivalenol were not detected. All the samples analysed had safe levels of mycotoxins tested but were contaminated by at least two mycotoxins that could pose some additive or synergistic health effects among consumers. On average: a 60 kg adult consuming 1-6 L/day of the beer was exposed to FB₁ + FB₂ at an estimated 2.20-13.20 μg/kg body weight/day. These values were far above the maximum tolerable daily intake of 2 μg/kg bw/day established by the Joint FAO/WHO Expert Committee on Food Additives (JECFA). The study demonstrates that consumption of umqombothi can significantly enhance dietary exposure to multiple mycotoxins among consumers, and therefore accentuates the need for strategies aimed at reducing toxigenic fungal colonization and mycotoxin contamination in the beer processing chain.

Aflatoxins and ochratoxin A in different cocoa clones (Theobroma cacao L.) developed in the southern region of Bahia, Brazil

Brazil is the sixth largest producer of cocoa beans in the world, after Côte d'Ivoire, Ghana, Indonesia, Nigeria and Cameroon. The southern region of Bahia stands out as the country's largest producer, accounting for approximately 60% of production. Due to damage caused by infestation of the cocoa crop with the fungus Moniliophthora perniciosa, which causes 'witch's broom disease', research in cocoa beans has led to the cloning of species that are resistant to the disease; however, there is little information about the development of other fungal genera in these clones, such as Aspergillus, which do not represent a phytopathogenicity problem but can grow during the pre-processing of cocoa beans and produce mycotoxins. Thus, the aim of this work was to determine the presence of aflatoxin (AF) and ochratoxin A (OTA) in cocoa clones developed in Brazil. Aflatoxin and ochratoxin A contamination were determined in 130 samples from 13 cocoa clones grown in the south of Bahia by ultra-performance liquid chromatography with a fluorescence detector. The method was evaluated for limit of detection (LOD) (0.05-0.90 μg kg^-1), limit of quantification (0.10-2.50 μg kg^-1) and recovery (RSD) (89.40-95.80%) for AFB₁, AFB₂, AFG₁, AFG₂ and OTA. Aflatoxin contamination was detected in 38% of the samples in the range of <LOD-17.795 μg kg^-1, with AFB₁ in 25% of the total samples, whereas ochratoxin A was positive in 18% of the samples in the range of <LOD-274.90 μg kg^-1.

Differential Adsorption of Ochratoxin A and Anthocyanins by Inactivated Yeasts and Yeast Cell Walls during Simulation of Wine Aging

The adsorption of ochratoxin A (OTA) by yeasts is a promising approach for the decontamination of musts and wines, but some potential competitive or interactive phenomena between mycotoxin, yeast cells, and anthocyanins might modify the intensity of the phenomenon. The aim of this study was to examine OTA adsorption by two strains of Saccharomyces cerevisiae (the wild strain W13, and the commercial isolate BM45), previously inactivated by heat, and a yeast cell wall preparation. Experiments were conducted using Nero di Troia red wine contaminated with 2 μg/L OTA and supplemented with yeast biomass (20 g/L). The samples were analyzed periodically to assess mycotoxin concentration, chromatic characteristics, and total anthocyanins over 84 days of aging. Yeast cell walls revealed the highest OTA-adsorption in comparison to thermally-inactivated cells (50% vs. 43% toxin reduction), whilst no significant differences were found for the amount of adsorbed anthocyanins in OTA-contaminated and control wines. OTA and anthocyanins adsorption were not competitive phenomena. Unfortunately, the addition of yeast cells to wine could cause color loss; therefore, yeast selection should also focus on this trait to select the best strain.

Saccharomyces cerevisiae cell wall components as tools for ochratoxin a decontamination

The aim of this study was to evaluate the usefulness of Saccharomyces cerevisiae cell wall preparations in the adsorption of ochratoxin A (OTA). The study involved the use of a brewer’s yeast cell wall devoid of protein substances, glucans obtained by water and alkaline extraction, a glucan commercially available as a dietary supplement for animals and, additionally, dried brewer’s yeast for comparison. Fourier Transform Infrared (FTIR) analysis of the obtained preparations showed bands characteristic for glucans in the resulting spectra. The yeast cell wall preparation, water-extracted glucan and the commercial glucan bound the highest amount of ochratoxin A, above 55% of the initial concentration, and the alkaline-extracted glucan adsorbed the lowest amount of this toxin. It has been shown that adsorption is most effective at a close-to-neutral pH, while being considerably limited in alkaline conditions.

Selection of autochthonous Saccharomyces cerevisiae strains as wine starters using a polyphasic approach and ochratoxin A removal

Over the last few years, the selection of autochthonous strains of Saccharomyces cerevisiae as wine starters has been studied; however, researchers have not focused on the ability to remove ochratoxin A (OTA) as a possible trait to use in oenological characterization. In this article, a polyphasic approach, including yeast genotyping, evaluation of phenotypic traits, and fermentative performance in a model system (temperature, 25 and 30°C; sugar level, 200 and 250 g liter(-1)), was proposed as a suitable approach to select wine starters of S. cerevisiae from 30 autochthonous isolates from Uva di Troia cv., a red wine grape variety grown in the Apulian region (Southern Italy). The ability to remove OTA, a desirable trait to improve the safety of wine, was also assessed using enzyme-linked immunosorbent assay. The isolates, identified by PCR-restriction fragment length polymorphism analysis of the internal transcribed spacer region and DNA sequencing, were differentiated at strain level through the amplification of the interdelta region; 11 biotypes (I to XI) were identified and further studied. Four biotypes (II, III, V, VIII) were able to reduce OTA, with the rate of toxin removal from the medium (0.6 to 42.8%, wt/vol) dependent upon the strain and the temperature, and biotypes II and VIII were promising in terms of ethanol, glycerol, and volatile acidity production, as well as for their enzymatic and stress resistance characteristics. For the first time, the ability of S. cerevisiae to remove OTA during alcoholic fermentation was used as an additional trait in the yeast-selection program; the results could have application for evaluating the potential of autochthonous S. cerevisiae strains as starter cultures for the production of typical wines with improved quality and safety.

Simultaneous determination of aflatoxin B1, aflatoxin B2, mycophenolic acid and sterigmatocystin in grape pomace by UHPLC-MS/MS

A reliable ultrahigh performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method was developed for the simultaneous determination of aflatoxin B1, aflatoxin B2, mycophenolic acid and sterigmatocystin in grape pomace. The samples were extracted by acetonitrile aqueous solution and further purified using a solid-phase extraction-based homemade clean-up cartridge. Next, the analytes were separated on a reversed-phase C18 column with a mobile phase consisting of water and acetonitrile. The separated compounds were detected with a tandem quadrupole mass spectrometer operating in positive electro-spray ionisation mode using multiple reaction monitoring. The established method was extensively validated by determining linearity (R2≯0.999), recovery (97.5-102.8%) and precision (relative standard deviation ≤7.0%). This method was then used for the simultaneous determination of the four mycotoxins in grape pomace samples.

In vitro removal of ochratoxin A by two strains of Saccharomyces cerevisiae and their performances under fermentative and stressing conditions

AIMS

The aim of this research was to study the effect of time, temperature, sugar content and addition of diammonium phosphate (DAP) on ochratoxin A (OTA) removal by two strains of Saccharomyces cerevisiae using a completely randomized design.

METHODS AND RESULTS

The strains were grown in a medium containing OTA (2 μg l(-1)), two sugar levels (200 and 250 g l(-1)), with or without DAP (300 mg l(-1)), and incubated at 25-30°C. The yeasts were able to decrease the toxin amount by c. 70%, with the highest removing effect observed after 3 days at 30°C in the presence of 250 g l(-1) of sugars and with DAP; after 10 days, the toxin was partially released into the medium. The strains produced high ethanol and glycerol contents, showed high tolerance to single/combined stress conditions and possessed β-d-glucosidase, pectinase and xylanase activities.

CONCLUSIONS

Ochratoxin A removal was affected by time, temperature, sugar and addition of DAP. Moreover, the phenomenon was reversible.

SIGNIFICANCE AND IMPACT OF THE STUDY

Ochratoxin A removal could be an interesting trait for the selection of promising strains; however, the strains removing efficiently the toxin could release it back; thus, the selection of the starter should take into account both the removal and the binding ability of OTA.

Ochratoxin A removal by Saccharomyces cerevisiae strains: effect of wine-related physicochemical factors

BACKGROUND

This study investigated the effect of some physicochemical parameters on the removal of ochratoxin A (OTA) by yeasts.

RESULTS

Two wild strains of Saccharomyces cerevisiae (W47 and Y28) were used to assess OTA removal under various conditions of temperature, pH, ethanol content and incubation time. All samples were analysed for OTA concentration by enzyme-linked immunosorbent assay (ELISA). In addition, yeast oenological traits were investigated: qualitative and technological traits were assessed on appropriate laboratory media, while the main products of microfermentation (sugars, ethanol, glycerol, acetic acid) were evaluated by Fourier transform infrared spectroscopy (FTIR). The results showed OTA reduction by 36-42% in cultures containing 100 g L⁻¹ ethanol incubated at pH 3.5 and 37 °C.

CONCLUSION

OTA removal was affected by contact time, pH and ethanol content, as it was increased at low pH and by 100 g L⁻¹ ethanol. Moreover, the phenomenon was reversible, as OTA was lowest after 4 days, then it was partially released in the medium.

A Saccharomyces cerevisiae wine strain inhibits growth and decreases Ochratoxin A biosynthesis by Aspergillus carbonarius and Aspergillus ochraceus

The aim of this study was to select wine yeast strains as biocontrol agents against fungal contaminants responsible for the accumulation of ochratoxin A (OTA) in grape and wine and to dissect the mechanism of OTA detoxification by a Saccharomyces cerevisiae strain (DISAABA1182), which had previously been reported to reduce OTA in a synthetic must. All of the yeast strains tested displayed an ability to inhibit the growth of Aspergillus carbonarius both in vivo and in vitro and addition of culture filtrates from the tested isolates led to complete inhibition of OTA production. S. cerevisiae DISAABA1182 was selected and further tested for its capacity to inhibit OTA production and pks (polyketide synthase) transcription in A. carbonarius and Aspergillus ochraceus in vitro. In order to dissect the mechanism of OTA detoxification, each of these two fungi was co-cultured with living yeast cells exposed to yeast crude or to autoclaved supernatant: S. cerevisiae DISAABA1182 was found to inhibit mycelial growth and OTA production in both Aspergilli when co-cultured in the OTA-inducing YES medium. Moreover, a decrease in pks transcription was observed in the presence of living cells of S. cerevisiae DISAABA1182 or its supernatant, while no effects were observed on transcription of either of the constitutively expressed calmodulin and β-tubulin genes. This suggests that transcriptional regulation of OTA biosynthetic genes takes place during the interaction between DISAABA1182 and OTA-producing Aspergilli.

Inhibition of A. carbonarius growth and reduction of ochratoxin A by bacteria and yeast composites of technological importance in culture media and beverages

Five composites of yeast and six of bacterial isolates from fermented products were studied, in order to assess their ability to inhibit Aspergillus carbonarius growth and reduce OTA concentration in culture media and beverages. The antagonistic effect of the above composites against A. carbonarius growth was studied in synthetic grape medium of pH 3.5 and a(w) 0.98, 0.95, 0.92 after incubation at 25°C. Different combinations of initial inocula of bacteria or yeast composites and fungi were used (10(2)cfu/mL vs 10(5)spores/mL; 10(5)cfu/mL vs 10(2)spores/mL; and 10(5)cfu/mL vs 10(5)spores/mL). Regarding the OTA reduction experiment, 10(3) and 10(7)cfu/mL of the bacteria and yeast composites were inoculated in liquid media of different pH (3.0, 4.0, 5.0, and 6.1 or 6.5) and initial OTA concentration (50 and 100μg/L) and incubated at 30°C. Moreover, grape juice, red wine, and beer were supplemented with 100μg/L of OTA and inoculated with composites of 16 yeasts (16YM) and 29 bacterial (29BM) strains (10(7)cfu/mL) to estimate the kinetics of OTA reduction at 25°C for 5days. Fungal inhibition and OTA reduction were calculated in comparison to control samples. None of the bacterial composites inhibited A. carbonarius growth. The high inoculum of yeast composites (10(5) cfu/mL) showed more efficient fungal inhibition compared to cell density of 10(2) cfu/mL. All yeast composites showed higher OTA reduction (up to 65%) compared to bacteria (2-25%), at all studied assays. The maximum OTA reduction was obtained at pH 3.0 by almost all yeast composites. For all studied beverages the decrease in OTA concentration was higher by yeasts (16YM) compared to bacteria (29BM). The highest OTA reduction was observed in grape juice (ca 32%) followed by wine (ca 22%), and beer (ca 12%). The present findings may assist in the control of A. carbonarius growth and OTA production in fermented foodstuffs by the use of proper strains of technological importance.

Modification of aflatoxin B1 and ochratoxin A toxicokinetics in rats administered a yeast cell wall preparation

The cell wall of Saccharomyces cerevisiae can bind mycotoxins in vitro, but there is scarce information on whether this property decreases the absorption of mycotoxins in vivo. The effect of a yeast cell wall preparation (YCW) on toxicokinetics and balance excretion (urine and faeces) of aflatoxin B(1) (AFB1) and ochratoxin A (OTA) was tested in rats after oral administration of each toxin. The (3)H-labelled mycotoxins were used at low doses. Co-administration of YCW with AFB1 decreased the extent, but not the rate, of absorption. Concurrently, radioactivity excreted in faeces increased by up to 55% when compared with controls, whilst the excretion in urine decreased (p < 0.05). The effect of YCW on OTA was less marked, although it increased radioactivity excretion in faeces (up to 16%; p < 0.05) it did not result in changes in urine and toxicokinetic parameters. The in vivo effect is in agreement with the reported in vitro binding ability for these toxins (AFB1 > OTA). In conclusion, these results indicate that YCW could be used to protect monogastric animals against exposure to low dietary levels of selected mycotoxins.

Chemical, physical and biological approaches to prevent ochratoxin induced toxicoses in humans and animals

Ochratoxins are polyketide derived fungal secondary metabolites with nephrotoxic, immunosuppressive, teratogenic, and carcinogenic properties. Ochratoxin-producing fungi may contaminate agricultural products in the field (preharvest spoilage), during storage (postharvest spoilage), or during processing. Ochratoxin contamination of foods and feeds poses a serious health hazard to animals and humans. Several strategies have been investigated for lowering the ochratoxin content in agricultural products. These strategies can be classified into three main categories: prevention of ochratoxin contamination, decontamination or detoxification of foods contaminated with ochratoxins, and inhibition of the absorption of consumed ochratoxins in the gastrointestinal tract. This paper gives an overview of the strategies that are promising with regard to lowering the ochratoxin burden of animals and humans.