Aspergillus Section Nigri Isolates Research Articles

Description and management of Aspergillus section Nigri causing post-harvest bulbs rot of onion

When onions are improperly stored, a post-harvest disease known as black mold of onion bulbs can result in considerable economic losses. Aspergillus section Nigri, one of many species, has been implicated in the development of black mold. In the present study, rot onion bulbs were collected from markets in Qena, Egypt. Thirteen Aspergillus section Nigri isolates were obtained and identified by morphological and molecular characterization. The ochratoxins potential of isolated A. section Nigri was tested, and three isolates were producers at the range of 1.5–15 ppm. For the presence of pks gene, no amplification product was detected. Using the fungal growth inhibition test, the isolates of A. niger were inhibited by eco-friendly materials Cement and Zeolite. Cement exhibited maximum percentage growth inhibition against the tested isolates at 74.7–86.7%. The pathogenicity activity of the A. niger isolates was tested by inoculation of healthy onion bulbs, other onion bulbs covered with Cement and Zeolite before inoculation by A. niger was used. The two treatments significantly reduced bulbs rot disease of onion than untreated bulbs. Seven and nine isolates showed 0% rot on covered bulbs by Cement and Zeolite, respectively as compared with inoculated onions, which exhibited rot ranging from 55 to 80%. Using eco-friendly materials with efficiency against post-harvest bulbs rot of onion was evaluated in this study.

Ochratoxin A Contamination of California Pistachios and Identification of Causal Agents.

Ochratoxin A (OTA) is a potent mycotoxin produced by Aspergillus and Penicillium spp., which contaminates many crops, including pistachios. Pistachios contaminated with OTA may be subjected to border rejections resulting in significant economic losses to the United States agricultural revenues. The current study examined prevalence of OTA in California-grown pistachios and identified its causal agents. OTA was detected in 20% of samples from 2018 to 2021 (n = 809), with 18% of samples exceeding the European Union regulatory limit of 5 μg/kg. Fungi potentially responsible for OTA contamination were isolated from leaves, nuts, and soil collected from 14 pistachio orchards across California. A total of 1,882 isolates of Aspergillus section Nigri and 85 isolates of section Circumdati were recovered. Within section Nigri, 216 (11.5%) isolates were identified as potential OTA producers using a boscalid-resistance assay. Phylogenetic analyses of partial gene sequences for β-tubulin and calmodulin genes resolved section Circumdati into four species: A. ochraceus (33%), A. melleus (28%), A. bridgeri (21%), and A. westerdijkiae (19%). A. westerdijkiae produced the highest levels of OTA in inoculated pistachios (47 μg/g), followed by A. ochraceus (9.6 μg/g) and A. melleus (3.3 μg/g). A. bridgeri did not produce OTA. OTA production by section Circumdati was optimal from 20 to 30°C. All 216 boscalid-resistant isolates from section Nigri were identified as A. tubingensis, and representative isolates (n = 130) produced 3.8 μg/kg OTA in inoculated pistachios. This is the first detailed report on OTA contamination and causal fungi in California pistachios and will be helpful in devising effective management strategies.

Invasive Factors Recognition in Aspergillus Section Nigri Isolates from Patient and Environmental Samples in the Centre Region, Cameroon

Background: Aspergillus section Nigri species are invasive opportunistic pathogens, seen in individuals with various immune disorders. The invasive capacity involves the production of varieties of enzymes such as lipases, phospholipase, proteases and hyaluronidase. The determination of proteinase, phospholipase, esterase and biofilm production in patient and environmental isolates approve the pathogenic strength of the species.
 Aims: To evaluate the invasive capacity of Aspergillus section Nigri isolates from patients and environmental samples.
 Methods: Our study is cross sectional and experimental, performed at the outpatient clinic of the otorhinolaryngology department of Central and University teaching hospital during a period of 12 months from March 2018 to February 2019. To determine the invasive capacity of Aspergillus section Nigri species, 400 samples were evaluated in the study (that is; 250 from patients and 150 samples from environment). Patient samples and hospital environment samples were evaluated by standard phenotypic methods for detecting of Proteinase, phospolipase, esterase and biofilm. The variables were statistically analyzed using Chi-square test of independent and SPSS (Version 16.0).
 Results: The isolates recovered from the patient sample shows maximum invasive capacity as compared to the environmental isolates, that is for 44 isolates; 42 isolates showed proteinase activity and biofilm production, followed by phospholipase activity 36, and then esterase 32.The isolates recovered from the hospital environment also showed the production of the various invasive factors, that is for 16 isolates; 15 isolates showed biofilm production, followed by proteinase activity 6, phospholipase 5 and esterase 4.The disparities of the invasive capacity in patient and environment isolates virulence were statistically significant for proteinase, phospholipase and esterase ( that is; p-value <0.05). Majority the isolates recovered from patients and the environment were potential producers of biofilm.
 Conclusion: The isolates recovered from patients sample showed high invasive capacity as compare to the isolates recovered from the environment. This highlights the implications of phospholipase enzyme, proteinase enzyme, esterase enzyme and biofilm used by Aspergillus section Nigri isolates as means of survival in the host system.

Occurrence of aflatoxin- and ochratoxin A-producing Aspergillus species in Thai dried chilli

The present study aimed to examine the presence of aflatoxin- and ochratoxin A (OTA)-producing fungi in dried chilli ( Capsicum spp.). A total of 120 chilli samples, including 60 samples each of chilli powder and dried chilli pods, were examined for fungal contamination. Results showed that 86.7% and 96.7% of chilli powder and dried chilli pods, respectively, were contaminated by fungi at a concentration of <10 3 CFU/g. Overall, 500 fungal isolates were recovered and identified using a morphological method. The most frequent strain was Aspergillus section Flavi (46.6%), followed by Aspergillus section Nigri (34%), Penicillium (7.6%), Aspergillus section Aspergillus (7.6%), Aspergillus section Circumdati (2.2%) and Rhizopus (2%). In total, 37.5% and 43.8% of Aspergillus section Flavi isolates obtained from dried chilli powder and dried chilli pods, respectively, produced aflatoxin. Of the 96 aflatoxigenic isolates, 96.9% of the strains produced aflatoxin B and 3.1% produced both aflatoxin B and G. However, β-tubulin sequence analysis revealed that all aflatoxin-producing isolates were identical to A. flavus . Moreover, 170 isolates of Aspergillus section Nigri , 11 of Aspergillus section Circumdati , 2 of Aspergillus section Flavi producing yellow-to-cinnamon colonies and 38 of Penicillium spp. were examined for their ability to produce OTA. In total, 1 isolate of Aspergillus section Nigri and 2 isolates of Aspergillus section Flavi produced OTA. The first isolate was identified as A. carbonarius , whereas the latter two isolates were both A. alliaceus . The highest OTA production by A. carbonarius (622.4 ng/g) was observed following incubation on MEA at 25 °C for 21 days. Conversely, the two A. alliaceus isolates produced OTA at levels of 583.7 and 743.7 ng/g, respectively, after cultivation on YES at 25 °C for 21 days. To the best of our knowledge, this is the first report regarding the natural occurrence of aflatoxin- and OTA-producing fungi in dried chilli from Thailand. • More than 95% of dried chilli powder and dried chilli pods collected in Thailand was contaminated with fungi. • Aspergillus section Flavi is the most common species in dried chilli. • Aspergillus section Flavi in dried chili samples is frequently aflatoxigenic strain. • Ochratoxin A producing species, A. carbonarius and A. alliaceus , were detected in dried chilli powder.

Genotypic identification of ochratoxigenic Aspergilli that contaminated beef luncheon and their protease activity

Twenty-six fungal species belonging to 10 genera were collected from 40 beef luncheon samples marketed in the Qena city on Czapek–Dox agar at 28 °C. A. section Nigri and A. flavus were the most prevalent species among isolated fungi; they were contaminating 65% and 50% of the luncheon samples. According to the phylogenetic analysis using β-tubulin gene, the selected A. section Nigri was identified as A. niger and A. tubingensis. All selected isolates belonging to A. niger and A. tubingensis showed positive results for the presence of the PKS gene. Using VICAM fluorometer, the average level of ochratoxin A was found to range from 4.1 to 7.1 and 4.6 to 8.2 ppm for A. tubingensis and A. niger, respectively. All Aspergillus section Nigri isolates were protease producers except two isolates belonging to A. tubingensis. A significant difference was observed in protease production between A. tubingensis and A. niger (P = 0.005); the most active protease producers were AnL 12 and 19 (A. niger) and AtL 3 and 4 (A. tubingensis) were weak producers.

Species identification, antifungal susceptibility, and clinical feature association of Aspergillus section Nigri isolates from the lower respiratory tract.

Species of Aspergillus section Nigri are generally identified by molecular genetics approaches, whereas in clinical practice, they are classified as A. niger by their morphological characteristics. This study aimed to investigate whether the species of Aspergillus section Nigri isolated from the respiratory tract vary depending on clinical diagnosis. Forty-four Aspergillus section Nigri isolates isolated from the lower respiratory tracts of 43 patients were collected from February 2012 to January 2017 at the National Hospital Organization (NHO) Tokyo National Hospital. Species identification was carried out based on β-tubulin gene analysis. Drug susceptibility tests were performed according to the Clinical and Laboratory Standards Institute (CLSI) M38 3rd edition, and the clinical characteristics were retrospectively reviewed. A. welwitschiae was isolated most frequently, followed by A. tubingensis. More than half of the A. tubingensis isolates exhibited low susceptibility to azoles in contrast to only one A. welwitschiae isolate. Approximately three quarters of the patients from whom A. welwitschiae was isolated were diagnosed with colonization, whereas more than half the patients from whom A. tubingensis was isolated were diagnosed with chronic pulmonary aspergillosis (CPA). More attention needs to be given to the drug choice for patients with CPA with Aspergillus section Nigri infection because A. tubingensis, which was found to be frequently azole-resistant, was the most prevalent in these patients.

Species identification, antifungal susceptibility, and clinical feature association of Aspergillus section Nigri isolates from the lower respiratory tract.

Species of Aspergillus section Nigri are generally identified by molecular genetics approaches, whereas in clinical practice, they are classified as A. niger by their morphological characteristics. This study aimed to investigate whether the species of Aspergillus section Nigri isolated from the respiratory tract vary depending on clinical diagnosis. Forty-four Aspergillus section Nigri isolates isolated from the lower respiratory tracts of 43 patients were collected from February 2012 to January 2017 at the National Hospital Organization (NHO) Tokyo National Hospital. Species identification was carried out based on β-tubulin gene analysis. Drug susceptibility tests were performed according to the Clinical and Laboratory Standards Institute (CLSI) M38 3rd edition, and the clinical characteristics were retrospectively reviewed. A. welwitschiae was isolated most frequently, followed by A. tubingensis. More than half of the A. tubingensis isolates exhibited low susceptibility to azoles in contrast to only one A. welwitschiae isolate. Approximately three quarters of the patients from whom A. welwitschiae was isolated were diagnosed with colonization, whereas more than half the patients from whom A. tubingensis was isolated were diagnosed with chronic pulmonary aspergillosis (CPA). More attention needs to be given to the drug choice for patients with CPA with Aspergillus section Nigri infection because A. tubingensis, which was found to be frequently azole-resistant, was the most prevalent in these patients.

Clinical and microbial epidemiology of otomycosis in the city of Yasuj, southwest Iran, revealing Aspergillus tubingensis as the dominant causative agent.

Otomycosis is a mycotic infection of the external auditory canal and can be caused by a wide range of fungal species. In this study, we aimed to identify fungal isolates from patients suspected of otomycosis. External ear canal samples were taken from patients referred to the outpatient department of Shahid-Mofatteh Clinic in the city of Yasuj, Iran, and examined by direct microscopy and culture. DNA of the isolated fungi was tested by internal transcribed spacer PCR restriction fragment length polymorphism analysis for identification of yeasts and β-tubulin sequencing for identification of Aspergillus species. Among 275 patients suspected of otomycosis, 144 cases (83 female and 61 male) were confirmed with otomycosis. For 89% (n=128) of positive cultures, microscopy was also positive, while there were no cases with a microscopy-positive and culture-negative result. The predominant predisposing factor was self-cleaning of the external ear using unhygienic tools, and the main risk occupation was 'housewife'. The most common isolated fungi were typically Aspergillus (n=120), including 73 isolates of Aspergillus section Nigri, 43 of section Flavi, 3 of section Terrei and 1 of section Fumigati. After sequencing, 44 out of 73 strains primarily identified as Aspergillus niger turned out to be Aspergillus tubingensis. Thirty-five isolates were identified as Candida, including Candida parapsilosis (n=22), Candida albicans (n=12) and Candida tropicalis (n=1). Aspergillus tubingensis was the most common species involved in otomycosis. This work corroborates the difficulty of precise identification of species within the black Aspergilli by morphological characteristics.

The eliminatory effects of cold argon plasma jet on aflatoxin B1 produced by different isolates of Aspergillus section nigri

Aflatoxin and ochratoxin are among the most resistant and severe toxins produced by Aspergillus spp. The aim of this study was an evaluation of eliminatory effects of cold argon plasma jet on aflatoxin B1. Sampling of wheat, corn, oatmeal, flour and rice products from northern cities of Iran was carried out. The fungal species were cultured on CHAPK medium and next to sabouraud dextrose broth + malt extract (SB + ME) and also SB + yeast extract (SB + YE) media to obtain aflatoxin B1. The ELISA test was conducted to measure the aflatoxin level. The mean initial concentration of the aflatoxin from charts analysis in the SB +ME medium was 16.106 μg / kg (10.4, 8.32 and 7.55 μg / kg at 30, 60 and 360 sec, respectively), and in the SB +YE medium from 23.699 μg / kg (12.82, 9.93 and 9.54 μg / kg, respectively), at the same time. Furthermore, the mean concentrations of aflatoxin B1 by tables analysis in the SB+ ME medium changed from 20.02 μg / kg to 6.87, 10.46 and 7.55 μg / kg, at 30, 60 and 360 sec, respectively, and in the medium SB +YE from 28.85 μg / kg reached 6.56.6, 8.43 and 7.02 μg / kg, respectively, at the same time. In this study, the change or decrease in the concentration of aflatoxin B1, from Lin/Log and Log/Lin analyses of charts was significant (p&lt;0.05) at 60 s and 360 s of application of the cold argon plasma jet in both media. The cold plasma as a new technology in various fields of food and agriculture can provide effective and suitable solutions in order to promote the goals of food industry, especially in the areas of mycotoxin elimination.

Fumonisin-production by Aspergillus section Nigri isolates from Japanese Foods and Environments.

Fumonisins are well known as mycotoxins produced by various Fusarium species. Recently Aspergillus niger has been reported to be a fumonisin B2 (FB2) producer. Aspergillus niger is a member of Aspergillus section Nigri. Members of this section are common food contaminants and are also distributed widely in the environment. This study aimed to determine 1) optimum culture conditions of A. niger for fumonisin production including growth medium, temperature and incubation period and 2) fumonisin production among isolates of Aspergillus section Nigri and closely related species isolated from Japanese food and environmental samples. Growth on Czapek yeast extract broth +5% NaCl (CYBS) at 28°C for 7 days resulted in the highest levels of FB2 production as determined by quantitative LC-MS/MS of culture extracts. Sixty-two isolates were collected from various foods in domestic markets as well as from soil and air. The isolates principally separated into two groups; A. niger and A. luchuensis/A. piperis/A. tubingensis, following molecular phylogenetic analysis. ELISA using the tip culture method was shown to be suitable for screening of the fumonisin-producing strains. Phylogenic analysis of Aspergillus section Nigri isolates from food and environmental samples indicated that fumonisin producing strains could be grouped into the A. niger clade. Nineteen of 35 (54%) isolates classified as A. niger were FB2 producers. The current study suggests that FB2-producing A. niger are distributed throughout several regions of Japan.

English

Section Nigri is among the most important from the genus Aspergillus, since it possesses economical and biotechnological properties. Its identification is considered quite hard and complex. Due to this fact, Aspergillus taxonomy has been carried out by morphological, biochemical and molecular data. Morphological characterization besides molecular analyses was performed to properly identify Aspergillus section Nigri. A set of 42 Aspergillus section Nigri isolates were obtained from Brazilian Atlantic Rainforest. From these isolates, 16.7% originated from leaf litter layer and 83.3%, from soil. The isolates were divided into three different groups according to analyzed characteristics. 26 were identified as Aspergillus aculeatus, 12 as Aspergillus aculeatinus and 4 belonged to a group called “Aspergillus niger Aggregate”, considered as biseriate. Key words: Fungi, taxonomy, morphological identification, polymerase chain reaction (PCR), ITS.

Mycobiota of spices and aromatic herbs

A total of 67 samples of spices and herbs were tested for mould contamination. From 50.7% of samples, moulds were not isolated. The most dominant genera were Aspergillus and Penicillium. Potential producers of mycotoxins Aspergillus spp. and Penicillium spp. were tested for the ability to produce some mycotoxins. Isolates of potentially toxinogenic species were found to produce various mycotoxins, namely alfatoxin B1 (Aspergillus flavus), cyclopiazonic acid (Aspergillus flavus), sterigmatocystin (Emericella nidulans), roquefortine C (Penicillium allii, P. chrysogenum, P. crustosum, P. expansum), penitrem A (P. crustosum) and patulin (P. expansum). Some of the tested isolates produce two mycotoxins: A. flavus (aflatoxin B1 and cyclopiazonic acid), P. crustosum (roquefortine C and patulin) and P. expansum (roquefortine C and patulin). None of the tested isolates of Aspergillus section Nigri screened, appeared to produce ochratoxin A. Totally 11 samples were analysed for the presence of aflatoxins and ochratoxin A. Aflatoxin B1 was found in 5 (45.5%) out of 11 samples analysed with levels ranging from 0.14 to 2.9 µg.kg-1. In one sample we detected aflatoxin G1. Ochratoxin A was found in 3 samples (27.3%), with levels ranging from 2.2 to 5.19 µg.kg-1. No sample was contaminated by aflatoxins or ochratoxin A above the maximum admitted threshold established by the European legislation.

Transformation of zearalenone to zearalenone-sulfate by Aspergillus spp.

The primary goal of this research was to assess the biotransformation of zearalenone (ZEA), an oestrogenic mycotoxin, into ZEA-sulfate by some Aspergillus section Nigri isolates. A. niger isolates were shown to be able to convert ZEA after 72 h of incubation at different ZEA concentrations (5 to 150 µg/ml). The product formula corresponding to ZEA-sulfate was determined by accurate mass measurement. This conjugate was shown to be less oestrogenic than ZEA using a MCF-7 proliferation assay. This study demonstrated that A. niger has the ability to transform ZEA over a broad range of ZEA concentrations (5 to 150 µg/ml) and that sulfonation could lead to a less toxic compound. These results are significant as little is known about the ability of fungi, and especially A. niger, to detoxify ZEA by sulfonation. This study could lead to a way of detoxifying feed naturally contaminated with mycotoxins.

ITS-RFLP characterization of black Aspergillus isolates responsible for ochratoxin A contamination in cocoa beans

In the present study, ochratoxigenic mycobiota in cocoa beans was identified at species level by digestion of the ITS products using the endonucleases HhaI, NlaIII and RsaI. Of the 132 isolates of Aspergillus section Nigri collected from cocoa beans, 89 were identified as A. tubingensis, 27 as A. niger, 10 as A. tubingensis-like and 6 as A. carbonarius. No variation was observed between RFLP patterns (C, N, T1 and T2) described previously for grape isolates and those of the cocoa isolates analysed. With respect to OTA-producing fungi, a high percentage of black aspergilli (50.7%) was able to produce OTA. Additionally, most of the OTA-producing isolates were of moderate toxigenicity, producing amounts of OTA from 10 μg g−1 to 100 μg g−1. Percentages of OTA-producing isolates in the A. niger aggregate were higher than in other substrates, ranging from 30% to 51.7%. Furthermore, the detected levels of OTA production in the A. niger aggregate, particularly in A. tubingensis species was higher than in A. carbonarius, ranging from 0.7 μg g−1 to 120 μg g−1 (mean 24.55 μg g−1). Due to the high occurrence, percentage of ocratoxigenic isolates and their ability to produce OTA, isolates belonging to the A. niger aggregate could be considered as the main cause of OTA contamination in cocoa beans used for manufacturing cocoa products.

Water activity and temperature effects on growth of Aspergillus niger, A. awamori and A. carbonarius isolated from different substrates in Argentina

The objectives of this study were to determine the effect of water activity, temperature, and their interactions on a) mycelial growth rate and b) the lag phase prior to grow of seven isolates of Aspergillus section Nigri isolated from peanuts, maize kernels, dried grapes and coffee cherries from Argentina. Three Aspergillus niger, three A. awamori and one A. carbonarius isolates examined showed optimum a W level for growth at 0.97 with optimal temperature of 30 °C. for most of the isolates and 25 °C for only one ( A. awamori RCP176). Minimal a W for growth was 0.85 at the highest temperature tested. Overall growth was reduced up to 50% at 0.93 a W. Growth was also to a large extend inhibited at 0.85 a W for most isolates even after 21 days of incubation at temperatures lower than 30 °C. The analysis of variance of the effect of single (isolate, a W and temperature), two- and three-way interaction showed that all factors alone and all interactions were statistically significant ( P < 0.001) in relation to growth rates and lag phase for A. niger, A. awamori and A. carbonarius isolates. These data are relevant since these species are isolated in high frequency on numerous substrates for human and animal consumption in Argentina.

Occurrence of ochratoxin A producing fungi in wine and table grapes in Israel

A 3-year survey was conducted to assay the number of Aspergillus Section Nigri isolates and in vitro ochratoxin A (OTA) production capacity in 10 vineyards in Israel. The survey included field sampling of two wine cultivars, ‘Sauvignon Blanc’ and ‘Cabernet Sauvignon’ as well as the table grape cultivar ‘Superior’. A total of 2114 isolates were analyzed and of those 161 isolates were shown to produce OTA. The major finding was that Aspergillus carbonarius (336 tested strains) is the most consistent producer of OTA, with approximately 35% of the isolates identified as positive in vitro. In comparison, 3.1% of other isolates from the Aspergillus niger aggregate (of 1432 strains) produced OTA in vitro. In contrast, none of the 346 tested strains with a uniseriate head morphology produced OTA. The incidence of infected berries was very low before veraison, while at harvest, this frequency was twice as high. In general, the composition of black Aspergilli did not differ during berry development. Generally, more OTA-producing isolates were isolated from the surface of table grapes cv. ‘Superior’ compared to ‘Sauvignon Blanc’. None of the samples collected at harvest contained traces of OTA in the juice. This study shows that grapes in Israel are contaminated with ochratoxigenic species which represent a risk of OTA contamination.

Survey of the mycobiota of Spanish malting barley and evaluation of the mycotoxin producing potential of species of Alternaria, Aspergillus and Fusarium

The present work deals with the toxigenic mycobiota occurring in Spanish malting barley and the capability for producing mycotoxins by several important toxigenic fungi. One hundred and eighty seven samples of malting barley were gathered from Spanish breweries before processing. One hundred and fifty kernels per sample were surface-sanitized with a 2% sodium hypochlorite solution and incubated on three culture media. The most abundant fungi were species of Alternaria, Aspergillus, Penicillium and Fusarium, which were present in 93%, 82.3%, 57.8% and 27.8% of the samples, respectively. To evaluate their mycotoxin producing potential a number of isolates belonging to each genus, except Penicillium, were randomly selected and incubated on culture media known to be appropriate for production of mycotoxins. Alternariol and alternariol monomethyl ether were produced by 26.7% of Alternaria spp. isolates (all belonged to Alternaria alternata). All tested isolates of F. verticillioides produced fumonisin B 1 (FB 1) and 61.3% of them produced fumonisin B 2 (FB 2), whereas FB 1 was synthesized by 83.3% and FB 2 by 77.8% of F. proliferatum isolates. Twenty percent of the isolates of the Aspergillus flavus/ A. parasiticus group had the capability to produce aflatoxin B 1 and aflatoxin B 2. Thirty out of 34 isolates of F. graminearum produced deoxynivalenol and zearalenone whereas the other 4 isolates produced nivalenol. Ochratoxin A was detected in 75% and 15% of isolates of Aspergillus section Nigri and A. ochraceus, respectively. This is the first survey carried out in Spain on the toxigenic mycobiota contaminating malting barley in breweries and the mycotoxin producing capacity of several species. The information obtained is useful for assessing the risk of mycotoxins in beer.

Influence of water activity and temperature on growth of isolates of Aspergillus section Nigri obtained from grapes

The effects of water activity ( a w) and temperature on growth of Aspergillus section Nigri isolated from wine grapes were investigated on an agar medium with composition similar to that of grapes. Temperatures in the range of 10–37 °C were tested. Optimum temperatures for growth were between 30 and 37 °C. Water activity levels ranging from 0.90 to 0.995 were tested. Optimum a w for growth was 0.98 in most cases. Statistical differences were found among the groups tested ( A. carbonarius, A. niger aggregate and A. section Nigri uniseriates). Growth rates models for the factors assayed have been obtained.

Influence of water activity and temperature on growth of isolates of Aspergillus section Nigri obtained from grapes

The effects of water activity ( a w ) and temperature on growth of Aspergillus section Nigri isolated from wine grapes were investigated on an agar medium with composition similar to that of grapes. Temperatures in the range of 10–37 °C were tested. Optimum temperatures for growth were between 30 and 37 °C. Water activity levels ranging from 0.90 to 0.995 were tested. Optimum a w for growth was 0.98 in most cases. Statistical differences were found among the groups tested ( A. carbonarius , A. niger aggregate and A . section Nigri uniseriates). Growth rates models for the factors assayed have been obtained.

Occurrence of ochratoxin A and toxigenic potential of fungal isolates from Spanish grapes

AbstractThis paper reports the results from an extensive survey of filamentous fungi isolated from wine‐producing grapes and their capacity to produce ochratoxin A (OTA) on Czapek Yeast Autolysate agar (CYA), in order to assess their potential for producing this toxin in grapes. Grapes were sampled from four Spanish wine‐producing regions during 2001. The fungal infection in berries increased with time, reaching 100% at harvest. A total of 386 isolates of Aspergillus section Nigri and 10 of Aspergillus section Circumdati were isolated and tested for their ability to produce OTA in CYA. 21 strains produced OTA (18 Aspergillus section Nigri and 3 Aspergillus section Circumdati). Aspergillus section Circumdati isolates produced higher amounts of OTA than Aspergillus section Nigri ones, with means of 10.76 µg g−1 CYA and 1.42 µg g−1 CYA, respectively. Despite this, black aspergilli are believed to be highly responsible for the OTA levels found in musts and wines, as it is more widespread in grapes. Musts (n = 40) produced from the grapes collected were analysed. 15% were found to contain OTA, concentrations ranging from 0.091 to 0.813 ng ml−1 (detection limit: 0.07 ng ml−1), but no correlation was found with the ochratoxigenic moulds isolated from grapes. Copyright © 2004 Society of Chemical Industry