Environment factors influence in vitro interspecific interactions between A. ochraceus and other maize spoilage fungi,growth and ochratoxin production

The effect of water availability (water activity,a_w; 0.995–0.90) and temperature (18–30 °) on in vitro interactions between an ochratoxin producing strain of Aspergillus ochraceus and six other spoilage fungi was assessed in dual culture experiments on a maize meal-based agar medium. Inprimary resource capture of nutrient substrate, A. ochraceus was dominant against many of the interacting species, being able to overgrow and replace A. candidus, and sometimes A. flavus and the Eurotium spp. regardless of a_w or temperature. However, with freely available water (0.995 a_w) A. alternata and A. niger were dominant, with mutual antagonism between A. ochraceus and A. flavus at 25–30 °C. In the driest conditions tested (0.90 a_w) there was also mutual antagonism between A. ochraceus and the two Eurotium spp. Overall, under allconditions tested the Index of Dominance for A. ochraceus was much higher than for other competing species combined suggesting that A. ochraceus wasa good competitive colonist able to replace a numberof other species. However, the growth rate ofA. ochraceus was modified and decreased by the interaction with competitors. Interaction between A. ochraceus and species such as A. alternata (18°C/0.995) and Eurotium spp. (0.995–0.95 and 25–30 °C) resulted in a significant stimulation of ochratoxin production. Theresults are discussed in relation to the effect that environmental factors have on the possible competitiveness of A. ochraceus in the maizegrain ecosystem and the role of ochratoxin in nicheexclusion of competitors. This revised version was published online in June 2006 with corrections to the Cover Date.     

Heat-stability of peroxidase in mycelia of some toxigenic and nontoxigenic Aspergilli and Penicillia

Seven-day-old mycelia from 19 cultures of Aspergillus and 12 cultures of Penicillium were heated to 50, 60, 65, 70, 75, 80, 85, 90 or 95 C for no more than min, and tested for residual peroxidase. The peroxidase from all aspergilli survived heating at 50 through 80 C. Peroxidase from toxigenic strains of Aspergillus flavus, Aspergillus parasiticus and Aspergillus ochraceus survived heating at 85 C and often at 90 C, whereas peroxidase from nontoxigenic strains of A. flavus was inactivated at 90 C and markedly reduced in activity at 85 C. Peroxidase from all penicillia survived heating at all temperatures through 80 C, although the activity of several cultures was reduced at 80 C. Peroxidase activity in mycelia of two strains of Penicillium cyclopium and one of Penicillium puberulum failed to survive heating at 85 C. One strain each of Penicillium roqueforti and Penicillium viridicatum exhibited some peroxidase activity after heating at 90 C, whereas the peroxidase of all other penicillia was inactivated at this temperature.     

Hydrolytic enzymes secreted by Paecilomyces lilacinus cultured on sclerotia of Aspergillus flavus

Sclerotia, the survival stage of Aspergillus flavus, are compact masses of mycelia capable of with-standing harsh climatic conditions. Six strains of Paecilomyces lilacinus, originally isolated from sclerotia of A. flavus var. flavus or A. flavus var. parasiticus, were also able to colonize the sclerotia from four different strains of A. flavus under laboratory conditions. P. lilacinus strains did not differ significantly in their colonization ability, but host susceptibility appeared to be an important factor. P. lilacinus strains were cultured in vitro for 96 h on a basal salt medium containing either ground sclerotia of A. flavus or glucose plus asparagine. Activities of hydrolytic enzymes such as polysaccharidases, proteases, and chitinases were determined in the culture supernatants. Supernatants from fungal cultures grown in the basal medium containing glucose plus aspargine medium showed very little or no enzyme activity, whereas fungi grown on ground sclerotia produced a variety of enzymes. Specifically, all strains produced chitinases (endochitinase and N-acetyl glucosaminidase), -1,3-glucanase, chymoelastase and chymotrypsin, suggesting that these enzymes may be required for colonization of sclerotia. Production of -1,4-glucanase, dextranase, cellulase, and trypsin was strain variable, suggesting that these enzymes may not be required.The mention of firm names or trade products does not imply that they are endorsed or recommended by the U.S. Department of Agriculture over other firms or similar products not mentioned Correspondence to: S. C. Gupta     

The Use of Micromycetes for Cleaning Parts of Aircraft Engines

Mycelial fungi Penicillium funiculosum, P. citrinum, P. expansum, P. chrysogenum, Aspergillus ochraceus, A. alliaceus, A. luchaensis, A. flavus, and A. niger were isolated from enrichment cultures. These fungi actively destruct carbon deposits formed during operation of aircraft. A biotechnological method for removing fouling from parts of aircraft engines (PAE) was developed. This method is less laborious, more rapid, and ecologically cleaner than contemporary chemical methods. Scanning microscopy was suggested for estimating the degree of decarbonization of PAE surfaces.     

Mycotoxins of fungal strains from stored herbal plants and mycotoxin contents of Nigerian crude herbal drugs

The ability of fungi isolated from stored herbal drug plants to produce mycotoxins in semisynthetic media was studied. The results obtained show that aflatoxins and ochratoxin A, were produced by Aspergillus flavus, A. parasiticus and A. ochraceus isolates. The time-production courses of aflatoxins B₁, B₂, ₁ and ochratoxin A in crude herbal drug preparations show that more of these toxins were produced with increase in time of storage of the drugs. The results indicate that the potential exists for the toxigenic strains to elaborate mycotoxins in a large quantity in herbal drug substrates than in semisynthetic media.This revised version was published online in October 2005 with corrections to the Cover Date.     

Decolourisation and dephenolisation potential of selected <Emphasis Type="Italic">Aspergillus</Emphasis> section <Emphasis Type="Italic">Nigri</Emphasis> strains – <Emphasis Type="Italic">Aspergillus tubingensis</Emphasis> in olive mill wastewater

Aspergillus section Nigri strains Aspergillus aculeatus Ege-K 258, A. foeditus var. pallidus Ege-K156, A. niger Ege-K 4 and A. tubingensis Ege-K 265 were used to treat olive mill wastewater (OMW) in an investigation aimed at exploring their dephenolisation and decolourisation ability and, consequently, the economic feasibility of using any or all of these strains in a pre-treatment step in the processing of OMW. Of these strains A. tubingensis Ege-K 265 resulted in an 80% decolourisation of twofold-diluted OMW and a 30% decolourisation of undiluted OMW; in addition, it was able to remove approximately 30% of all phenolic compounds in both twofold-diluted and undiluted OMW. We conclude that A. tubingensis Ege-K 265 could be effectively used in the pre-treatment step of a combined aerobic-anaerobic process to solve the environmental problems caused by OMW in Mediterranean countries.     

White-rot fungi capable of decolourising textile dyes under alkaline conditions

Twelve white-rot fungal strains belonging to seven different species were screened on plates under alkaline condition to study the decolourisation of the textile dyes Reactive Black 5 and Poly R-478. Three strains of Trametes versicolor (Micoteca da Universidade do Minho (MUM) 94.04, 04.100 and 04.101) and one strain of Phanerochaete chrysosporium (MUM 94.15) showed better decolourisation results. These four strains were used for decolourisation studies in liquid culture medium. All four selected strains presented more efficient decolourisation rates on Reactive Black 5 than on Poly R-478. For both dyes on solid and liquid culture media, the decolourisation capability exhibited by these strains depended on dye concentration and pH values of the media. Finally, the decolourisation of Reactive Black 5 by T. versicolor strains MUM 94.04 and 04.100 reached 100 %. In addition, the highest white-rot fungi ligninolytic enzyme activities were found for these two strains.     

Biodegradation of Kerosene by Aspergillus flavus Using Statistical Experimental Designs

The ability of different local fungal isolates to degrade kerosene in liquid medium was studied. The results showed that the percent of kerosene degradation varied among the different tested fungi and that 60–96% of kerosene was degraded after 7 days in the presence of 0.2% (v/v) of Tween 80. The absence of the surfactant led to about 28.34% decrease of biodegradation. The degradation of 2% (v/v) of kerosene by the most efficient fungus (Aspergillus flavus) was significantly influenced by the incubation period and the composition of culture medium. Statistical experimental designs were used to optimize the process of kerosene degradation by the fungus. Under optimized medium compositions and culture conditions, A. flavus degraded kerosene (100%) after 111.3 h of incubation. Optimal conditions obtained in this work provided a solid foundation for further use of A. flavus in treatment of kerosene-polluted soil. The optimized conditions were applied to bioremediate 2.5% (v/w) kerosene-polluted soil by A. flavus, and the fungus efficiently degraded kerosene after 35 days of incubation.     

Decolourization of Black Oxidized Olive-Mill Wastewater by a New Tannase-Producing Aspergillus flavus Strain Isolated from Soil

Summary By contaminating a Tunisian soil with black oxidized and sterilized olive-mill wastewaters (OMW), 30 new indigenous fungal soil strains able to overcome the OMW toxicity could be directly selected. Ten of the fungal strains previously isolated were screened for their capability to grow in a liquid culture medium containing oxidized OMW as the only source of carbon and energy. According to these preliminary tests, strain F2 showed the best capability of removing black colour and COD (chemical oxygen demand) and was further identified as Aspergillus flavus. After optimization of batch-liquid culture conditions in the presence of oxidized OMW, the time course of biomass and enzyme production by A. flavus F2 was followed in relation to colour and COD removal. A. flavus F2 could efficiently decolourize and detoxify the black oxidized OMW (58 and 46% of colour and COD removal, respectively, after 6 days of cultivation), concomitantly with the production of tannase (8000 UI/l on day 3).     

Behaviour of Aspergillus flavus in presence of Aspergillus niger during biosynthesis of aflatoxin B1

Aspergillus niger or Aspergillus tamarii when grown as mixed cultures with toxigenic A. flavus inhibits biosynthesis of aflatoxin by A. flavus, owing primarily to its ability to produce inhibitors of aflatoxin biosynthesis and to their ability to degrade aflatoxin. Gluconic acid partly prevents aflatoxin production. The other factors such as changes in pH of the medium and the effect on the growth of A. flavus have no role in imparting capabilities to these cultures to inhibit aflatoxin production by A. flavus.     

Bio-activity of fungal culture filtrates against root-knot nematode egg hatch and juvenile motility and their effects on growth of mung bean (Vigna radiata L. Wilczek) infected with the root-knot nematode,Meloidogyne incognita

Culture filtrates of selected soil fungi, namely Aspergillus flavus, Aspergillus fumigatus, Aspergillus niger, Fusarium oxysporum, Penicillium vermiculatum and Rhizopus nigricans exhibited variable response to egg hatching and mortality of the root-knot nematode, Meloidogyne incognita. Higher concentrations of the culture filtrates of all the fungi inhibited egg hatching and proved to be toxic to the juveniles of M. incognita. In addition, development of the gall and multiplication of M. incognita were also found adversely affected in varying degrees on all the plants of Vigna radiata treated with the filtrates. The culture filtrate of A. niger showed highest toxicity to the nematode than those of any other fungus tested. Soil drench application of the culture filtrates gave better seedling growth and least nematode multiplication in comparison to seed soaking treatment.     

FT-IR Spectroscopy for Rapid Differentiation of Aspergillus flavus, Aspergillus fumigatus, Aspergillus parasiticus and Characterization of Aflatoxigenic Isolates Collected from Agricultural Environments

In agricultural areas, Aspergillus flavus, Aspergillus fumigatus and Aspergillus parasiticus are commonly identified in various feedstuffs and bioaerosols originated from feed handling. Some isolates belonging to these fungal species could produce mycotoxins and constitute a risk factor for human and animal health. In this study, Fourier-transform infrared spectroscopy was used for a rapid detection and characterization of 99 isolates collected from agricultural areas. The results showed a first cluster corresponding to strains previously attributed to the A. fumigatus group according to current taxonomic concepts, and a second cluster divided in 2 groups around reference strains of A. flavus and A. parasiticus species. The toxigenic capacity of isolates was evaluated by high performance liquid chromatography coupled to mass spectrometry. In the A. flavus group, only 6 strains of A. parasiticus and 4 strains of A. flavus were able to produce aflatoxins on culture media. FT-IR spectroscopy, respectively, allowed the differentiation of non-toxigenic and toxigenic A. flavus and A. parasiticus isolates at 75 and 100%. Discrimination between toxigenic and non-toxigenic A. fumigatus was not possible because all of the isolates produced at least one mycotoxin.     

Proof of concept: could snake venoms be a potential source of bioactive compounds for control of mould growth and mycotoxin production

The objective was to screen 10 snake venoms for their efficacy to control growth and mycotoxin production by important mycotoxigenic fungi including Aspergillus flavus, Aspergillus westerdijkiae, Penicillium verrucosum, Fusarium graminearum and F. langsethiae. The Bioscreen C rapid assay system was used. The venoms from the Viperidae snake family delayed growth of some of the test fungi, especially F. graminearum and F. langsethiae and sometimes A. flavus. Some were also able to reduce mycotoxin production. The two most potent crude snake venoms (Naja nigricollis and N. siamensis; 41 and 43 fractions, respectively) were further fractionated and 83/84 of these fractions were able to reduce mycotoxin production by >90% in two of the mycotoxigenic fungi examined. This study suggests that there may be significant potential for the identification of novel fungistatic/fungicidal bioactive compounds as preservatives of raw and processed food commodities post-harvest from such snake venoms.     

Study of mixed function oxidase system in <Emphasis Type="Italic">Aspergillus ochraceus</Emphasis> (NCIM 1146)

Aspergillus ochraceus (NCIM-1146) has shown the ability to degrade cholesterol, camphor and naphthalene, when 96 h grown mycelium incubated in medium containing these organic compounds. Presence of higher level of electron transport components and biotransformation enzyme activity were observed in Aspergillus ochraceus, when grown in potato dextrose medium for 96 h. The enzyme activity preferred NADPH as a cofactor and shows inhibition in the presence of CO, indicating cytochrome P-450 mediated reactions. A significant increase in the levels of electron transport components and biotransformation enzyme activity were observed in presence of different inducers (viz. cholesterol, camphor, naphthalene, veratrole, phenobarbital, n-hexane, kerosene and saffola oil) when compared with mycelium incubated in same way with similar conditions for 2 min incubation. Analyses of the products of cholesterol and camphor using HPLC and GCMS confirm the degradation of these compounds.     

Viral influences on aflatoxin formation by Aspergillus flavus

Summary A nontoxigenic isolate of Aspergillus flavus (NRRL 5565) contains a viral genome consisting of 3 double-stranded RNA (ds-RNA) components with molecular weights of approximately 3 kb each. It thus shares a characteristical feature with a virus occuring in strains of Penicillium chrysogenum.Application of known inhibitors of doublestranded RNA virus synthesis results in stable aflatoxin formation by this originally nontoxigenic strain and the simultaneous loss of its ds-RNA traits. Since the inhibitor induced toxicity can be completely reverted by incubation with a virus from Penicillium chrysogenum (PcV), it is presumed that PcV or a functional related virus possibly constitutes the aflatoxin repressing determinant in Aspergillus flavus.     

Airborne fungi in the hospitals of metropolitan Delhi

Summary The fungal airspora of a large hospital in Delhi Metropolis was studied from May 1989 – April 1991, using Andersen Six Stage Volumetric Sampler and Burkard Personal Slide Sampler. Simultaneously, samples were also collected from outside the hospital to act as a control. Samplers were operated for 10 min. each time, at 10 - day intervals. Additional samples were also collected from different sections of 3 other hospitals. Some of the dominant forms encountered wereCladosporium spp.,Aspergillus flavus, Smut,Fusarium spp.,Aspergillus niger, Alternaria spp.,Penicillium citrinum, Aspergillus versicolor, andPenicillium oxalicum. Aspergillus flavus showed significantly high concentration inside hospital (n=66, x=53 CFU m^–3, p<0.05) as compared to outside air. The peak period for fungi was observed to be from June – September. The spore concentration was much lower in hospital units receiving filtered air as compared to control environment, but in naturally ventilated hospitals the concentration was similar to that of outside air.     

Studies on the mycoflora associated with sugarcane factory waste and pollution of River Nile in upper Egypt

Sixty-nine species and four varieties that belong to 28 genera of terrestial fungi were recovered from polluted and non-polluted water and mud samples on glucose and cellulose-Czapek's agar at 28°C. The most common species from the two substrates on the two types of media were Aspergillus flavus, A. fumigatus, A.niger, Cladosporium cladosporioides, Fusarium oxysporum, Mycosphaerella tassiana and Penicillium chrysogenum. Twenty-six species belonging to 14 genera were isolated from polluted (26 species and 14 genera) and non-polluted (17species and 10 genera) mud samples on Sabouraud's dextrose agar at 28°C. The most prevalent species were Acremonium retiulum, Alternaria alternata, Aspergillus flavus, Aphanoascus fulvescens, A. terreus, Aphanoascus sp., Penicillium funiculosum and Stachybotrys chartarum.     

Fungi associated with food and feed commodities from Ecuador

Freshly harvested soybean, rice and corn from farms and corn-based pelleted feeds were collected from ranches from the coastal and mountain regions in Ecuador during 1998, and assessed for fungal contamination. The most prevalent fungi on pelleted feed were Aspergillus flavus and Fusarium graminearum. The prevalent fungi recovered from soybean were F. verticillioides, F. semitectum, Aspergillus flavus and A. ochraceus. In rice, F. oxysporum was the most prevalent toxigenic fungal species recorded, followed by F. verticillioides and A. flavus. In corn, F. verticillioides was the most prevalent fungus isolated in both the coastal and mountain regions, with high isolation frequencies of A. flavus and A. parasiticus at the coast. Based on the toxigenic species recovered, ochratoxin A may pose a contamination risk for soybean. A higher probability of aflatoxin contamination of corn was found in the coastal samples compared to those of the mountain region, while a risk of fumonisin contamination of corn exists in both regions.This revised version was published online in October 2005 with corrections to the Cover Date.     

Genetic variability of aflatoxin B<Subscript>1</Subscript> producing <Emphasis Type="Italic">Aspergillus flavus</Emphasis> strains isolated from discolored rice grains

Twenty-two aflatoxin B₁ (AFB1) producing Aspergillus flavus strains were isolated from 1,200 discolored rice grain samples collected from 20 states across India and tested their potential to produce AFB1 on different agar media. Further these isolates were characterized through randomly amplified polymorphic DNA method. All the strains of A. flavus were produced AFB1 on yeast extract sucrose agar media and none of the strains on A. flavus and A. parasiticus agar. Among the 22 strains, two strains from Tamil Nadu (DRAf 009) and Maharashtra (DRAf 015) produced high amount of AFB1 in all the media tested. To assess the genetic variability in A. flavus, the isolates were analyzed by using random amplified polymorphic DNA markers. Isolates showed 17–80% similarity with standard culture of A. flavus (MTCC 2799).     

Inhibitory effects of condiments and herbal drugs on the growth and toxin production of toxigenic fungi

The effects of thirteen kinds of powdered herbal drugs and seven kinds of commercial dry condiments on the growth and toxin production ofAspergillus parasiticus, A. flavus,A. ochraceus, andA. versicolor were observed by introducing these substances into culture media for mycotoxin production.Of the twenty samples tested, cinnamon bark completely inhibited the fungal growth, while the others only inhibited the toxin production.The inhibitors were easily extracted from the samples with solvents such as hot water, chloroform, or ethanol.The extracts from coptis, philodendron bark, mustard, green tea leaves, and zanthoxylum completely inhibited the aflatoxin production ofA. parasiticus, however, they had little or no inhibitory effect againstA. flavus.