Brief in vitro study on Botrytis cinerea and Aspergillus carbonarius regarding growth and ochratoxin A

Aims: To evaluate the effect of Botrytis cinerea growth on ochratoxin A (OTA) production by Aspergillus carbonarius and degradation. Methods and Results: OTA‐producing A. carbonarius and B. cinerea were grown on grape‐like medium at 20°C for 7 days. Radii of colonies were daily recorded and OTA was analysed. In addition, each B. cinerea isolate was inoculated on grape‐like synthetic nutrient medium (SNM) paired with each A. carbonarius isolate at a distance of 45 mm. Botrytis cinerea isolates were also grown in OTA‐spiked SNM. Growth rates of B. cinerea and A. carbonarius were 20 and 7·5 mm day^?1, respectively. The growth of the colonies of each species stopped when they contacted each other in paired cultures. OTA production by A. carbonarius in the contact area was affected by B. cinerea, but no clear trend was observed. All B. cinerea isolates showed to degrade between 24·2% and 26·7% of OTA from spiked SNM. Conclusions: The ecological advantage of B. cinerea, in terms of growth rate, vs. OTA‐producing Aspergillus in some wine‐growing regions and its ability to degrade OTA may explain the low levels of this toxin in noble wines. Significance and Impact of the Study: At determinate conditions, the presence of B. cinerea in grapes with A. carbonarius may help in reducing OTA accumulation.     

Water and temperature relations of growth and ochratoxin A production by Aspergillus carbonarius strains from grapes in Europe and Israel

AIMS: This study investigated the in vitro effects of water activity (a(w); 0.85-0.987) and temperature (10-40 degrees C) on growth and ochratoxin A (OTA) production by two strains of Aspergillus carbonarius isolated from wine grapes from three different European countries and Israel on a synthetic grape juice medium representative of mid-veraison (total of eight strains). METHODS AND RESULTS: The synthetic grape juice medium was modified with glycerol or glucose and experiments carried out for up to 56 days for growth and 25 days for OTA production. The lag phase prior to growth, growth rates and ochratoxin production were quantified. Statistical comparisons were made of all factors and multiple regression analysis used to obtain surface response curves of a(w) x temperature for the eight strains and optimum growth and OTA production by A. carbonarius. The lag phase increased from <1 day at 25-35 degrees C and 0.98 a(w) to >20 days at marginal temperatures and water availabilities. Generally, most A. carbonarius strains grew optimally at 30-35 degrees C, regardless of solute used to modify a(w), with no growth at <15 degrees C. The optimum a(w) for growth varied from 0.93 to 0.987 depending on the strain, with the widest a(w) tolerance at 25-30 degrees C. There was no direct relationship among growth, environmental factors and country of origin of individual strains. Optimum conditions for OTA production varied with strain. Some strains produced optimal OTA at 15-20 degrees C and 0.95-98 a(w). The maximum OTA produced after 10 days was about 0.6-0.7 microg g(-1), with a mean production over all eight strains of 0.2 microg g(-1) at optimum environmental conditions. CONCLUSIONS: This work demonstrates that optimum conditions for OTA production are very different from those for growth. While growth rates differed significantly between strains, integration of the OTA production data suggests possible benefits for use of the information on a regional basis. SIGNIFICANCE AND IMPACT OF THE STUDY: Very little detailed information has previously been available on the ecology of A. carbonarius. This knowledge is critical in the development and prediction of the risk models of contamination of grapes and grape products by this species under fluctuating and interacting environmental parameters.     

Effect of temperature and water activity on growth and ochratoxin A production boundaries of two Aspergillus carbonarius isolates on a simulated grape juice medium

Aims: To develop and validate a logistic regression model to predict the growth and ochratoxin A (OTA) production boundaries of two Aspergillus carbonarius isolates on a synthetic grape juice medium as a function of temperature and water activity (a_w). Methods and Results: A full factorial design was followed between the factors considered. The a_w levels assayed were 0·850, 0·880, 0·900, 0·920, 0·940, 0·960, 0·980 and the incubation temperatures were 10, 15, 20, 25, 30, 35 and 40°C. Growth and OTA production responses were evaluated for a period of 25 days. Regarding growth boundaries, the degree of agreement between predictions and observations was >99% concordant for both isolates. The erroneously predicted growth cases were 3·4–4·1% false‐positives and 0·7–1·4% false‐negatives. No growth was observed at 10°C and 40°C for all a_w levels assayed, with the exception of 0·980 a_w/40°C, where weak growth was observed. Similarly, OTA production was correctly predicted with a concordance rate >98% for the two isolates with 0·7–1·4% accounting for false‐positives and 2·0–2·7% false‐negatives. No OTA production was detected at 10°C or 40°C regardless of a_w, and at 0·850 a_w at all incubation temperatures. With respect to time, the OTA production boundary shifted to lower temperatures (15–20°C) as opposed to the growth boundary that shifted to higher temperature levels (25–30°C). Using two literature datasets for growth and OTA production of A. carbonarius on the same growth medium, the logistic model gave one false‐positive and three false‐negative predictions out of 68 growth cases and 13 false‐positive predictions out of 45 OTA production cases. Conclusions: The results of this study suggest that the logistic regression model can be successfully used to predict growth and OTA production interfaces for A. carbonarius in relation to temperature and a_w. Significance and Impact of the Study: The proposed modelling approach helps the understanding of fungal‐food ecosystem relations and it could be employed in risk analysis implementation plans to predict the risk of contamination of grapes and grape products by A. carbonarius.     

Aspergillus carbonarius growth and ochratoxin A production on a synthetic grape medium in relation to environmental factors

AIMS: The effects of water activity (0.90-0.99 a(w)), temperature (15-37 degrees C), and their interaction on growth and ochratoxin A (OTA) production by eight isolates of Aspergillus carbonarius were investigated on synthetic nutrient medium (SNM) with composition similar to grapes. METHODS AND RESULTS: Growth data were modelled by an multiple linear regression and response surface models were obtained. Aspergillus carbonarius grew much faster at 30 degrees C than at the other temperature levels tested and its growth rate increased with increasing a(w), maximum growth rate being between 0.95 and 0.99 a(w). In general, isolates grew faster at 35-37 degrees C than at 20 degrees C, although no significant differences were found between these temperatures. OTA accumulation was also favoured by high a(w) levels, and although it was observed in the whole range of temperatures, maximum amounts were detected at 20 degrees C. No OTA was found at the most unfavourable growth conditions. CONCLUSIONS: Optimum a(w) level for growth seems to correspond with optimum for OTA production, meanwhile the most propitious temperature for the toxin production was below the best one for growth. SIGNIFICANCE AND IMPACT OF THE STUDY: Prediction of A. carbonarius growth would allow estimating their presence and therefore, the OTA production, as it was found that conditions for the toxin production were more limited than those permitting growth.     

Partitioning of ochratoxin A in mycelium and conidia of Aspergillus carbonarius and the impact on toxin contamination of grapes and wine

AIMS: Aspergillus carbonarius is an important ochratoxin A (OTA)-producing fungus which is responsible for toxin contamination of grapes and wine. The objectives of this study were to examine the partitioning of OTA in mycelium and conidia of a range of A. carbonarius strains on artificial grape juice and defined media, to determine the excretion patterns of OTA from these spores, and the effect of organic acids used in wine production on OTA excretion from conidia. METHODS AND RESULTS: The results showed that 60-70% of the OTA was accumulated in the conidia of a number of different isolates of A. carbonarius. Calculations showed that on different defined media, an amount of 0.011- to 0.1-pg OTA was present per conidium. The OTA in spores was found to be rapidly excreted into the medium during the initial few hours after conidial germination leading to an increase of OTA in must during maceration for wine production. The presence of tartaric acid inhibited OTA production, but malic acid enhanced this production during mycelial growth. These acids were also shown to affect the time course of germination and the rate of OTA excretion from conidia during germination. CONCLUSIONS: This study is the first to examine and show the partitioning of OTA into spores of strains of A. carbonarius and that rapid excretion of OTA from spores could be a reason for OTA accumulation in musts during wine production. SIGNIFICANCE AND IMPACT OF THE STUDY: Conidia of A. carbonarius could be a major source of OTA contamination of grapes used in wine production. This information could help in the development of effective prevention strategies to minimize wine contamination with this important mycotoxin.     

Utilization of AFLP markers for PCR-based identification of Aspergillus carbonarius and indication of its presence in green coffee samples

AIMS: The objective of this work was to test whether ochratoxin A (OTA) production of Aspergillus niger and A. carbonarius is linked to a certain genotype and to identify marker sequences with diagnostic value aiding identification of A. carbonarius, a fungus of major concern regarding OTA production in food and food raw materials. METHODS AND RESULTS: Aspergillus niger and A. carbonarius were isolated mainly from Brazilian coffee sources. The ability of isolates to produce OTA was tested by thin layer chromatography (TLC). Strains were genetically characterized by AFLP fingerprinting and compared with each other and with reference strains. Cluster analysis of fingerprints showed clear separation of A. niger from A. carbonarius strains. To obtain marker sequences, AFLP fragments were isolated from silver stained polyacrylamide gels, cloned and sequenced. Sequences obtained were used to develop species- specific PCR primers for the identification of A. carbonarius in pure culture and in artificially and naturally infected samples of green coffee. CONCLUSIONS: No clear correlation between genetic similarity of the strains studied and their potential to produce OTA was found. The PCR assays designed are a useful and specific tool for identification and highly sensitive detection of A. carbonarius. SIGNIFICANCE AND IMPACT OF THE STUDY: The developed PCR assays allow specific and sensitive detection and identification of A. carbonarius, a fungus considered to be one of the major causative agents for OTA in coffee and grape-derived products. Assays may provide powerful tools to improve quality control and consumer safety in the food processing industry.     

Aspergillus niger and Aspergillus carbonarius in Corinth Raisin and Wine-Producing Vineyards in Greece: Population Composition, Ochratoxin A Production and Chemical Control

Vineyard surveys of Corinth raisin cultivar carried out in the Peloponnese region of Greece during 2002 and of wine‐producing grape cultivars (Cabernet Sauvignon and Grenache Rouge) on the island of Rhodes, Greece, during 2003, demonstrated the occurrence of various Aspergillus spp. in berries of bunches at harvest. Aspergillus niger and A. carbonarius were predominantly isolated from sampled berries. Although the prevailing Aspergillus spp. isolates belonged mainly to A. niger aggregate, isolates of A. carbonarius were by far the most efficient Ochratoxin A (OTA) producers as revealed by the enzyme‐linked immunosorbent assay test. This study provides the first evidence concerning the composition of Aspergillus populations in raisin and wine‐producing vineyards and offers convincing data for their ability to produce various levels of OTA in Corinth raisins and wine‐producing grapes in Greece. Furthermore, it demonstrates that chemical applications with the fungicide Switch, especially under low to intermediate Aspergillus infection of vineyards, could both significantly reduce the occurrence of OTA‐producing Aspergillus spp. and restrict sour rot severity. In contrast, vineyard applications with the fungicides Carbendazim or Chorus were ineffective in controlling the fungus in Corinth raisin cultivar.     

Predictive assessment of ochratoxin A accumulation in grape juice based-medium by Aspergillus carbonarius using neural networks

Aims:  To study the ability of multi-layer perceptron artificial neural networks (MLP-ANN) and radial-basis function networks (RBFNs) to predict ochratoxin A (OTA) concentration over time in grape-based cultures of Aspergillus carbonarius under different conditions of temperature, water activity ( a _w) and sub-inhibitory doses of the fungicide carbendazim.
Methods and Results:  A strain of A. carbonarius was cultured in a red grape juice-based medium. The input variables to the network were temperature (20–28°C), a _w (0·94–0·98), carbendazim level (0–450 ng ml⁻¹) and time (3–15 days after the lag phase). The output of the ANNs was OTA level determined by liquid chromatography. Three algorithms were comparatively tested for MLP. The lowest error was obtained by MLP without validation. Performance decreased when hold-out validation was accomplished but the risk of over-fitting is also lower. The best MLP architecture was determined. RBFNs provided similar performances but a substantially higher number of hidden nodes were needed.
Conclusions:  ANNs are useful to predict OTA level in grape juice cultures of A. carbonarius over a range of a _w, temperature and carbendazim doses.
Significance and Impact of the Study:  This is a pioneering study on the application of ANNs to forecast OTA accumulation in food based substrates. These models can be similarly applied to other mycotoxins and fungal species.     

Specific detection of Aspergillus carbonarius by SYBR® Green and TaqMan® quantitative PCR assays based on the multicopy ITS2 region of the rRNA gene

Agroproducts contaminated by ochratoxin A (OTA) represent a risk for human and animal health and, therefore, maximum limits have been established by Food Safety Authorities. Reduction of OTA contamination may be accomplished by early detection of OTA-producing fungal species using rapid, specific and sensitive detection and quantification by PCR-based methods. Aspergillus carbonarius is one of the most important OTA-producing species, in particular in grapes and derivatives from Mediterranean regions. In this work, highly efficient quantitative PCR assays using SYBR Green I and TaqMan methods were developed for specific detection of A. carbonarius to be used in grapes. The primers and the TaqMan probe were based on the internal transcribed region 2 multicopy region (internal 2 sequence of the rRNA gene). The specificity and sensitivity of both assays were tested on genomic DNA mixtures of several A. carbonarius strains and other fungal species frequently present in grapes. Both methods were also compared using grapes inoculated with different spore concentrations of A. carbonarius , detecting up to 0.4 pg DNA g⁻¹ grape berries. The efficiency and sensitivity of both methods were comparable and only the lower cost of SYBR Green might favour its use in routine screenings.     

Interpretation of variability of mitochondrial genomes in the species Aspergillus carbonarius

For interpretation of intraspecific polymorphism and the considerable differences in the size of mtDNAs among three groups of A. carbonarius, restriction maps were constructed from several enzymes. Functional maps were also developed to compare genome organisations and gene content. The appearance of various mtDNAs of A. carbonarius strains are different in size, but their gene content is almost identical. The 1.1 kb size difference between two closely related subgroups (1a, 1b) can be attributed to the presence or absence of an intron in cox2 gene. This phenomenon demonstrates that the migration of introns is possibly responsible for the development of variable mitochondrial genomes in nature. The striking differences in size and restriction patterns between two main mtDNA groups might derive from both the intronal variations and the altered intergenic organisation.     

Aspergillus species producing ochratoxin A: isolation from vineyard soils and infection of Semillon bunches in Australia

AIMS: The incidence of toxigenicity among Australian isolates of Aspergillus niger and Aspergillus carbonarius was assessed. Aspergillus rot and concomitant production of ochratoxin A (OA) in bunches inoculated with A. carbonarius were also investigated. METHODS AND RESULTS: Aspergillus niger and A. carbonarius were isolated from vineyard soils. Aspergillus niger was more widespread than A. carbonarius, and two restriction fragment length polymorphism types of A. niger, N and T, were present. Three of 113 A. niger isolates and all 33 A. carbonarius isolates produced OA. Aspergillus carbonarius was inoculated onto Semillon bunches with and without damage in the month before harvest. Damaged berries at greater than 12.3 (o) Bx were particularly susceptible to Aspergillus rot and production of OA, which was concentrated in severely mouldy berries. CONCLUSIONS: OA in Australian grapes results mainly from infection of berries by A. carbonarius. It is concentrated in discoloured, shrivelled berries. The potential for Aspergillus rot and OA production appears to commence after veraison and increase with berry damage and ripeness. SIGNIFICANCE AND IMPACT OF THE STUDY: Minimizing damage to grapes between veraison and harvest significantly reduces Aspergillus rot and OA formation. Monitoring the extent of Aspergillus rot in bunches infected with toxigenic Aspergillus spp. may give some indication of OA contamination.     

Modelling the effect of temperature and water activity on growth of Aspergillus niger strains and applications for food spoilage moulds

AIMS: To develop a model for the combined effect of water activity (a(w)) and temperature on growth of strains of Aspergillus niger, and comparison with data on food spoilage moulds in the literature. METHODS AND RESULTS: An extended combined model describing the growth of two strains of A. niger, as a function of temperature (25-30 degrees C) and a(w) (0.90-0.99) was developed. The growth rate (micro) was expressed as the increase in colony radial growth per unit of time. This extends the previous square root model showing the relationship between temperature and bacterial growth rate developed by Ratkowsky et al. (1983) and the parabolic relationship between the logarithm of the growth rate and a(w) developed by Gibson et al. (1994). A good correlation between the experimental data and the model predictions was obtained, with regression coefficients (r(2)) > 0.99. In addition, the use of this model allowed predictions of the cardinal a(w) levels: a(w(min)), and a(w(opt)). The estimation of the minimum a(w) levels (a(w(min))) was in accordance with data in the literature for similar and a range of other Aspergillus and related species, regardless of the solutes used for a(w) modification. The estimation of the optimal a(w) (a(w(opt))) and the optimal growth rate (micro(opt)) were in good agreement with the experimental results and data from the literature. CONCLUSIONS: This approach enables accurate prediction of the combined effects of environmental factors on growth of spoilage fungi for rapid prediction of cardinal limits using surface response curves. SIGNIFICANCE AND IMPACT OF THE STUDY: This approach is a rapid method for predicting optimal and marginal conditions for growth of a wide range of spoilage micro-organisms in relation to interacting environmental conditions and will have applications for improving shelf-life of intermediate moisture foods.     

Modelling the effect of water activity and temperature on growth rate and aflatoxin production by two isolates of Aspergillus flavus on paddy

Aims: This study was conducted to characterize the growth of and aflatoxin production by Aspergillus flavus on paddy and to develop kinetic models describing the growth rate as a function of water activity (a_w) and temperature. Methods and Results: The growth of A. flavus on paddy and aflatoxin production were studied following a full factorial design with seven a_w levels within the range of 0·82–0·99 and seven temperatures between 10 and 43°C. The growth of the fungi, expressed as colony diameter (mm), was measured daily, and the aflatoxins were analysed using HPLC with a fluorescence detector. The maximum colony growth rates of both isolates were estimated by fitting the primary model of Baranyi to growth data. Three potentially suitable secondary models, Rosso, polynomial and Davey, were assessed for their ability to describe the radial growth rate as a function of temperature and a_w. Both strains failed to grow at the marginal temperatures (10 and 43°C), regardless of the a_w studied, and at the a_w level of 0·82, regardless of temperature. Despite that the predictions of all studied models showed good agreement with the observed growth rates, Davey model proved to be the best predictor of the experimental data. The cardinal parameters as estimated by Rosso model were comparable to those reported in previous studies. Toxins were detected in the range of 0·86–0·99 a_w with optimal a_w of 0·98 and optimal temperature in the range of 25–30°C. Conclusions: The influences of a_w and temperature on the growth of A. flavus and aflatoxin production were successfully characterized, and the models developed were found to be capable of providing good, related estimates of the growth rates. Significance and Impact of the Study: The results of this study could be effectively implemented in minimizing the risk of aflatoxin contamination of the paddy at postharvest.     

Potential of ochratoxin A production by Aspergillus carbonarius strains isolated from grapes at different ecological factors

Aspergillus carbonarius is known to colonize and produce ochratoxin A (OTA) on grapes and its derived products which is harmful to humans. We screened and tested A. carbonarius strains which isolated from grapes for production of OTA and selected three high OTA producing strains (ACSP1, ACSP2, ACSP3) for this study. These strains were further tested for their ability to produce OTA at different ecological factors [temperature 15, 25, 30, 35°C; water activity (a_w) 0.98, 0.95, 0.90, 0.88; and pH 4.0, 7.0, 9.0, 10.0]. Out of the three strains tested, A. carbonarius ACSP3 produced high levels of OTA than ACSP2 and ACSP1 in all the ecological factors. At 30°C A. carbonarius strains produced the highest OTA compared with other temperature regimes. With reference to water activity, a_w 0.98 favoured mycelial growth and accumulation of more OTA with all the three A. carbonarius strains. Further, pH 4.0 was encouraged the greatest production of OTA in all the strains. No growth was observed at a_w 0.88 and pH 10.0 in all the three strains except the strain ACSP3 at high pH. Our work demonstrated that temperature 30°C, a_w 0.98 and pH 4.0 is optimum for growth and production of OTA by A. carbonarius strains. Maximum amounts of OTA were found at earlier growth stages (7–9 days of incubation) in all the strains of A. carbonarius. The present study revealed that different ecological factors had great impact on OTA production by A. carbonarius which is useful for understanding OTA contamination and to develop proper management practices in future research programmes.     

Mycelial growth and ochratoxin A production by Aspergillus section Nigri on simulated grape medium in modified atmospheres

Aims:  To evaluate the impact of modified atmosphere packaging on in vitro growth of Aspergillus carbonarius and Aspergillus niger , and possible effects on ochratoxin A (OTA) biosynthesis.
Methods and Results:  Ochratoxigenic isolates belonging to the species A. carbonarius and A. niger were grown on a synthetic grapejuice medium (SNM) and packaged in combinations of controlled O₂ (1% and 5%) and CO₂ levels (0% and 15%), and in air as a control. Colony diameters were recorded every 3 days up to 21 days, and OTA was analysed after 7, 14 and 21 days. The greatest reductions in mycelial growth rate were observed at 1% O₂ followed by 1% O₂/15% CO₂, whereas 5% O₂ stimulated the growth of all isolates. OTA production by A. carbonarius and A. niger isolates was minimized at 1% O₂/15% CO₂ and 1% O₂, respectively, after 7 days of incubation. Maximal OTA accumulation after 7 days was observed for all isolates in the control pack and at 5% O₂.
Conclusions:  Of the atmospheres tested, only 1% O₂ combined with 15% CO₂ consistently reduced fungal growth and OTA synthesis by A. carbonarius and A. niger .
Significance and Impact of the Study:  Storage under modified atmospheres is unlikely to be suitable as the sole method for OTA minimization and grape preservation; other inhibitory factors are necessary.     

Growth and ochratoxin A production by Aspergillus carbonarius at different pHs and grape maturation stages

Aims: The objective of this work was to study the effect of some factors, linked to grape composition during ripeness process, on the growth and ochratoxin A (OTA) production of Aspergillus carbonarius isolated from grapes. Methods and Results: Aspergillus carbonarius isolates were tested (i) in vitro, in Czapek yeast autolysate agar (CYA) at different pHs (2·5–4·5) and incubation times (2–6 days), and (ii) in situ, in fresh grapes collected at different maturation stages. Aspergillus carbonarius was able to grow with the same intensity at the different maturation stages and pH levels tested. In general, a similar trend of OTA production by A. carbonarius in response to acidity in media and in grape was observed. Low pH level seemed optimal for maximum OTA production. Conclusions: Aspergillus carbonarius strains can strongly grow and produce OTA on grape from the early stages of maturation. Extrinsic environmental conditions at the harvest period and skin thickness are, probably, the mains factors contributing to OTA contamination of grapes at the end of maturation. Significance and Impact of the Study: The results lead to a better understanding of the critical point during grape maturation for the growth of ochratoxigenic fungi and the toxin production.     

Influence of water activity, temperature and time on mycotoxins production on barley rootlets

AIMS: The objective of this study was to determine the ochratoxin (OT) and aflatoxin (AF) production by three strains of Aspergillus spp. under different water activities, temperature and incubation time on barley rootlets (BR). METHODS AND RESULTS: Aspergillus ochraceus and Aspergillus flavus were able to produce mycotoxins on BR. Aspergillus ochraceus produced ochratoxin A (OTA) at 0.80 water activity (a(w)), at 25 and 30 degrees C as optimal environmental conditions. The OTA production varies at different incubation days depending on a(w). Aflatoxin B(1) (AFB1) accumulation was obtained at 25 degrees C, at 0.80 and 0.95 a(w), after 14 and 21 incubation days respectively. Temperature was a critical factor influencing OTA and AFB(1) production. CONCLUSIONS: This study demonstrates that BR support OTA and AFB(1) production at relatively low water activity (0.80 a(w)) and high temperatures (25-30 degrees C). SIGNIFICANCE AND IMPACT OF THE STUDY: The study of ecophysiological parameters and their interactions would determine the prevailing environmental factors, which enhance the mycotoxin production on BR used as animal feed.     

Incubation time and water activity effects on ochratoxin A production by Aspergillus section Nigri strains isolated from grapes

AIMS: The objective of this study was to determine the temporal ochratoxin A (OTA) accumulation profile of Aspergillus section Nigri at different water activity (aw) levels. METHODS AND RESULTS: Two Aspergillus carbonarius and two Aspergillus niger aggregate strains isolated from grapes were tested in vitro for OTA accumulation at 25 degrees C on synthetic nutrient medium, over periods of 20 days at different aw levels. Results were modelled by a multiple linear regression and response surface predictive models were obtained. High levels of aw favoured OTA production by these moulds. Maximum amounts of OTA were found at the earlier growth states (5 days for A. carbonarius and 7-13 days for A. niger aggregate). CONCLUSIONS: Provided that A. section Nigri, and mainly A. carbonarius, play the main role in OTA presence in grapes, it would be critical to adjust the harvest and processing time to significantly reduce the chances for OTA accumulation. SIGNIFICANCE AND IMPACT OF THE STUDY: Ochratoxin A production by A. section Nigri has been shown for the first time to occur optimally after as little as 5 days on a grape-like medium.     

Isolation, Structure elucidation, and antimycobacterial properties of dimeric naphtho-gamma-pyrones from the marine-derived fungus Aspergillus carbonarius

Two new dimeric naphtho-gamma-pyrones, compounds 1 and 2, were isolated from the AcOEt extract of the fungal strain WZ-4-11 of Aspergillus carbonarius, together with eight known analogues, including 10,10'-bifonsecin B (3), 6'-O-demethylnigerone (4), nigerone (5), isonigerone (6), fonsecin (7), rubrofusarin B (8), TMC 256A1 (9), and flavasperone (10). Their structures were elucidated by means of UV, CD, IR, and 1D- and 2D-NMR spectroscopy, in combination with HR-MS analysis. The fully assigned (1)H- and (13)C-NMR data of 3, and the (13)C-NMR data of 6 are reported for the first time. Compounds 1 and 2 showed weak antimycobacterial activities against Mycobacterium tuberculosis H37Rv, with MIC values of 43.0 and 21.5 microM, resp.