Yeast Extract Sucrose Broth Research Articles

Efficiency evaluation of ordinary and nanoscale extracts of Agaricus bisporus. on inhibition mycelial growth and aflatoxin production of Aspergillus flavus in maize grain

This study aimed to protect maize crops from infection and production of Aspergillus flavus (A. flavus) aflatoxin B1(AFB1), using the ordinary and nanoscale extracts of Agaricus spp. HPLC technology showed that the isolate taken from Musayyib district which coded with (AFA5) was a highest toxin producer. AFB1 at a concentration of 77.02 ppb. PCR product showed that the amplification of the ITS4- region was successful ITS1 according to the primers used, where a single bundle with a size of 744 bp (base pair) appeared. The isolated and diagnostic results of maize samples collected from separate sites showed the presence of A. flavus and different genera of fungi, namely Aspergillus spp., Fusarium spp., Penicillium spp., and Rhizopus spp., issued by the genus Aspergillus spp. with frequency rates of 18.33, 38.87, 20.19, 15.92, and 6.69 % respectively. On Potato Dextrose Agar (PDA), inhibitory effect results of Agaricus bisporus (A. bisporus) extract in inhibiting A. flavus growth, with inhibition percentages for the ordinary extract of 43.95, 34.59, and 10.90%, respectively, and for the nano extract 18.74, 43.71, and 76.56 % at 250,500 and 100 ppm respectively. AFB1 production was reduced by adding A. bisporus extracts (ordinary and nano) to Yeast Extract Sucrose Broth (YES) medium by 66% and 72.14%, respectively. Overall, our study presented a new insight for future scientific researches possibility of biocompands production using nanotechnology from natural resources that have the ability to safely environmentally control on mycotoxins production that present in agricultural production especially maize grains and encourage to widespread commercially use.

Inhibitory Effects of Bacillus subtilis Isolated from Meju (Fermented Soybean Brick) on the Growth of Aspergillus parasiticus

Background: Meju is a base material for making soy sauce, soybean paste, and red chili pepper paste, which are representative ingredients of Korean cuisine. Objectives: This study aimed to isolate a predominant bacterial strain of B. subtilis from meju and to observe its inhibitory effects on an aflatoxigenic mold. Methods: We used yellow soybeans (Glycine max (L.) Merr.) grown in South Korea, and meju was produced according to the recommended methods of the Korea Food Research Institute. The identification of the strain was conducted based on its morphological and biochemical characteristics and 16S rDNA sequence. Evaluation of the bacterial effect against A. parasiticus ATCC 15517 was done in yeast extract–sucrose broth at 28 °C. Its inhibitory effect was evaluated using two approaches: mycelial weight and aflatoxin production. Aflatoxins were determined using high-performance liquid chromatography. Results: In the meju samples fermented for three months, a B. subtilis strain, K-0924 was identified. At the end of the incubation period of A. parasiticus, dry mycelial weight was significantly reduced by more than 80% (p < 0.01) and total aflatoxin production was inhibited by more than 63% (p < 0.05) in the presence of B. subtilis. Conclusions: These results indicate that B. subtilis K-0924 inhibits the growth and aflatoxin production of toxigenic Aspergillus, which can be contaminated with meju. We could expect more inhibition by other bacteria related to fermentation of meju, and further examination is necessary on species other than B. subtilis.

Genome analysis of Pseudomonas strain 4B with broad antagonistic activity against toxigenic fungi.

Pseudomonas sp. 4B isolated from the effluent pond of a bovine abattoir was investigated as antifungal against toxigenic fungi. The complete genome of Pseudomonas 4B was sequenced using the Illumina MiSeq platform. Phylogenetic analysis and genome comparisons indicated that the strain belongs to the Pseudomonas aeruginosa group. In silico investigation revealed gene clusters associated with the biosynthesis of several antifungals, including pyocyanin, rhizomide, thanamycin, and pyochelin. This bacterium was investigated through antifungal assays, showing an inhibitory effect against all toxigenic fungi tested. Bacterial cells reduced the diameter of fungal colonies, colony growth rate, and sporulation of each indicator fungi in 10-day simultaneous growing tests. The co-incubation of bacterial suspension and fungal spores in yeast extract-sucrose broth for 48h resulted in reduced spore germination. During simultaneous growth, decreased production of aflatoxin B1 and ochratoxin A by Aspergillus flavus and Aspergillus carbonarius, respectively, was observed. Genome analysis and in vitro studies showed the ability of P. aeruginosa 4B to reduce fungal growth parameters and mycotoxin levels, indicating the potential of this bacterium to control toxigenic fungi. The broad antifungal activity of this strain may represent a sustainable alternative for the exploration and subsequent use of its possible metabolites in order to control mycotoxin-producing fungi.

Enhancement of Anti-MRSA Potential Produced by an Endophytic Fungus Ceratobasidium Ramicola IBRLCM127 via Submerged Fermentation System

Introduction: Exploring endophytic fungi isolated from medicinal herbs could be a turning point in the research of secondary metabolites biosynthesis, as these endophytic fungi are capable of synthesizing the similar compounds as their host plant. The advantages of manipulating endophytic fungi for bioactive compound production are the reduction of dependency rate on slow-growing and rare plants, cost-effective, continuous process, environmentally friendly and high yield in a short period. Thus, the current study envisages investigating the influence of culture conditions against the anti-MRSA potential production of the endophytic fungal isolate, Ceratobasidium ramicola IBRLCM127 isolated from the local medicinal plant Curcuma mangga Valeton & Zijp. Methods: The endophytic fungal isolate was used to produce fungal metabolites through submerged fermentation. The physical parameter improvement was investigated using the ‘one-factor-at-a-time’ technique. The fungal fermentative broth was subjected to an anti-MRSA assay using Lorian method, whereas the growth of a fungus was determined based on the cell growth weight. Results: The highest anti-MRSA potential of 42.50±0.1 U/ml and 5.49±0.1 g/L of mycelial growth was observed after improving the basal medium containing yeast extract sucrose broth incorporated with water extract from the host plant, 6 days old of inoculum age, 2 agar plugs of mycelia, incubation temperature of 25 0C and 12 days of cultivation 12 days of cultivation shaken at 120 rpm in the absence of light. Conclusion: The improved culture conditions shorten the incubation period and yield a significant enhancement of anti-MRSA potential and fungal growth with 13.27% and 10.91%, respectively.

Anti-yeast activity of endophytic fungi isolated from medicinal herb Ocimum sanctum with emphasis on Candida albicans

Endophytic fungi, Lasiodiplodia pseudotheobromae IBRL OS-64 and Muscodor sp. IBRL OS-94 were previously isolated from the leaf of medicinal plant, Ocimum sanctum was screened for their anti-yeast activity against pathogenic yeast. Both fungal isolates were cultivated in submerged fermentation using yeast extract sucrose broth as culture medium enriched with plant water extract and incubated for 20 d at 30°C with an agitation speed of 120 rpm. Preliminary study via agar plug diffusion assay revealed that both fungal isolates possess a fair anti-yeast activity against three out of four test yeast including Candida albicans, C. utilis and Rhodotorula rubra. On the disk diffusion assay, the ethyl acetate extract of L. pseudotheobromae IBRL OS-64 and Muscodor sp. IBRL OS-94 showed significant anti-yeast activity with the size of the inhibition zone ranging in between 9.6±0.5 - 21.3±0.5 mm and 14.4±0.5 - 20.2±0.7 mm respectively. As for ethyl acetate extract from L. pseudotheobromae OS-64, the MIC and MYC values were in the range of 500 – 1000 μg/mL and 2000 – 8000 μg/mL respectively. On the other hand, the MIC and MYC values of ethyl acetate extract of Muscodor sp. OS-94 ranged between 250 – 500 μg/mL and 1000 – 4000 μg/mL respectively. The time-kill assay demonstrated that the growth of C. albicans cell was dose-dependent in which the extract concentration was lower and higher than the MIC value showing yeastostatic and yeastocidal effects respectively. The scanning and transmission electron microscopes observation revealed that the candidal cells expose to extract experienced severity of morphological deterioration which led to cell death beyond repair and thus suggesting that the fungal extract could be a potential anti-candidal agent.

Effect of Lactic Acid Bacteria Strains on the Growth and Aflatoxin Production Potential of Aspergillus parasiticus, and Their Ability to Bind Aflatoxin B1, Ochratoxin A, and Zearalenone in vitro.

The increased consumption of plant-based foods has intensified the concern related to mycotoxin intoxication. This study aimed to investigate the effect of selected lactic acid bacteria (LAB) strains on the growth of Aspergillus parasiticus NRRL 2999 and its production of aflatoxin (AF). The ability of the heat-killed (100°C for 1 h) LAB strains to bind aflatoxin M1 (AFM1) in milk and aflatoxin B1 (AFB1), ochratoxin A (OTA), and zearalenone (ZEN) in potassium phosphate buffer (PPB) was also evaluated in vitro. Ten LAB strains were tested individually, by inoculating them simultaneously with the fungus or after incubation of the fungus for 24 or 48 h at 25°C. Double layer yeast extract sucrose (YES) agar, de Man Rogosa and Sharpe (MRS) agar, and YES broth were incubated for 7 days at 25°C to follow the development of the fungus. Levilactobacillus spp. 3QB398 and Levilactobacillus brevis 2QB422 strains were able to delay the growth of A. parasiticus in YES broth, even when these strains were inoculated 24 h after the fungus. The inhibitory effect of these LAB strains was confirmed by the reduction of fungus colony size, suggesting dominance of LAB by competition (a Lotka-Voltera effect). The production of AFB1 by A. parasiticus was inhibited when the fungus was inoculated simultaneously with Lactiplantibacillus plantarum 3QB361 or L. plantarum 3QB350. No AFB1 was found when Levilactobacillus spp. 2QB383 was present, even when the LAB was inoculated 48 h after the fungus. In binding studies, seven inactivated LAB strains were able to promote a reduction of at least 50% the level of AFB1, OTA, and ZEN. This reduction varied depending on the pH of the PPB. In milk, however, only two inactivated LAB strains were able to reduce AFM1, with a reduction of 33 and 45% for Levilactobacillus spp. 3QB398 (Levilactobacillus spp.) and L. brevis 2QB422, respectively. Nevertheless, these results clearly indicate the potential of using LAB for mycotoxin reduction.

Toxigenicity and phylogeny of Aspergillus section Flavi in poultry feed in Iran.

Background and Purpose:This study was conducted to evaluate the presence of aflatoxigenic strains and level of aflatoxin in poultry feed. Aflatoxigenic strains were investigated in corn and soybean meal as the ingredients of poultry feed, as well as in two types of commercial feed, namely pellet and mash. The gene sequencing was performed to identify the species of Aspergillus section Flavi.Materials and Methods:All samples were randomly collected from feed storage silos located in Iran in 2018. The samples were cultured on specialized media for 2 weeks at 28ºC. Identification of Aspergillus section Flavi isolates was based on macro- and microscopic morphological criteria and molecular analysis. The thin-layer chromatography (TLC) was applied to confirm the aflatoxigenic isolates. In addition, the level of aflatoxin B1 (AFB1) produced by these isolates was determined by high-performance liquid chromatography. The strains were subjected to sequence analysis, and Bt2 PCR products were purified by the QIAquick PCR purification kit. At the final stage, the phylogenetic tree was built.Results:Among 54 isolates identified as Aspergillus section Flavi, 20 (37%) isolates were found to produce aflatoxin at a range of 11.28±1.18 to 2239.92±92.26 µg/g fungal dry weight. The aflatoxigenic isolates had the frequencies of 45%, 40%, 10%, and 5% in the corn, pellet, soybean meal, and mash samples, respectively. Furthermore, the mean concentrations of AFB1 were significantly higher in the corn samples (707.04±39.05) than that of other poultry feed samples (P<0.05). A total of 34 (63%) isolates were detected as non-aflatoxigenic on the yeast extract-sucrose broth in TLC analysis. The toxigenic isolates produced the highest (2232.62±55.49) and lowest (11.28±1.18) levels of AFB1 in the corn samples, compared to other feedstuffs. Furthermore, the mean level of AFB1 in mash product was 554.09±10.36 µg/g, compared to a mean level of 229.22±11.09 µg/g in pellets. The isolates were randomly selected, sequenced, and then analyzed. Subsequently, the phylogenetic tree of Aspergillus section Flavi was plotted.Conclusion:The process of converting raw ingredients to compound poultry feed is more hazardous when there is not enough time and temperature provided to eliminate aflatoxigenic isolates. Therefore, Aspergillus section Flavi in poultry feed can pose a threat to the poultry industry and poultry products, thereby affecting the health status of humans. Unprocessed/processed materials, such as corns and pelleted feed, need further monitoring, especially when conditions are not optimal for destroying the fungus.

Impact of some environmental factors on growth and ochratoxin A production by Aspergillus niger and Aspergillus welwitschiae

Ochratoxin A (OTA) is a nephrotoxic mycotoxin which may contaminate various foods and feed products worldwide. Aspergillus niger is one of the species responsible for OTA contamination in grapes and derived products. This species has recently been split into A. niger and Aspergillus welwitschiae. Both species can not be distinguished by phenotypic or extrolite profiles and to date there is no ecophysiological information of A. welwitschiae.The aim of this study was to determine the effects of water activity (aw) (0.90; 0.95 and 0.98–0.99), culture media (Yeast Extract Sucrose Broth (YESB); Synthetic Grape Juice Medium (SGM); White grape juice (WGJ)) and temperature (15 °C, 25 °C and 35 °C) on the growth and OTA production of four strains of A. niger and six strains of A. welwitschiae. The assay was performed in microtiter plates, determining the absorbance at 530 nm and the concentration of OTA at 1, 2, 4 and 10 days.No significant differences were observed in absorbance and OTA values between the two species under study. The highest absorbance values were recorded in YESB, followed by SGM and WGJ. Absorbance values increased with increasing aw and temperature. The highest OTA values were obtained at 0.98–0.99 aw and the best culture media for OTA production was YESB, followed by WGJ and SGM. The studied strains of A. niger produced the highest mean OTA level at 25 °C whereas A. welwitschiae strains produced the highest mean OTA concentration at 15 °C, although not differing significantly from concentration produced at 25 °C.To our knowledge, this is the first report on the impact of some environmental factors on growth and OTA production by A. welwitschiae.

English

The endophytic fungi isolated from leaves of Ocimum sanctum Linn. of different ages were examined for antimicrobial activity. The agar plug diffusion assay was used for primary screening. A total of 148 fungal endophytes were successfully isolated and cultured but only 134 of them (90.5%) exhibited inhibitory activity towards at least one test microorganisms. Moreover, the colonization rate indicated that the old leaves were frequently and densely colonized by endophytes. The results suggested that healthy leaves at older stages of growth can be a potential source for the isolation of endophytic fungi with antimicrobial properties. The ethyl acetate extract prepared from the fermentative broth exhibited better antimicrobial activity and it suggested the antimicrobial activity of the isolates was affected by the culture medium. A better antimicrobial activity was observed in the yeast extract sucrose broth as compared to malt extract broth. Significant improvements in the antimicrobial activity of the crude extract were observed after addition of water extract of the host plant in the culture medium. Key words: Ocimum sanctum Linn., endophytic fungi, antimicrobial activity, host plant extract.

Occurrence of Penicillium brocae and Penicillium citreonigrum, which Produce a Mutagenic Metabolite and a Mycotoxin Citreoviridin, Respectively, in Selected Commercially Available Rice Grains in Thailand.

Commercially available rice grains in Thailand were examined to isolate the monoverticillate Penicillium species responsible for toxic yellowed rice. Penicillium species were obtained from seven out of 10 rice samples tested. Among them, one Penicillium citreonigrum isolate and six Penicillium brocae isolates were morphologically identified. The P. citreonigrum isolate produced the mycotoxin citreoviridin on a yeast extract sucrose broth medium. Mycotoxin surveys showed that citreoviridin was not detected in any samples, but one out of 10 rice samples tested was positive for aflatoxin B1 at a level of 5.9 μg/kg. An Ames test revealed that methanol extracts from rice grains inoculated with selected P. brocae isolates were positive for strains TA100 and YG7108 of Salmonella typhimurium, suggesting the presence of base-pair substitution and DNA alkylation mutagens. Our data obtained here demonstrated that aflatoxin B1 and toxic P. citreonigrum were present on domestic rice grains in Thailand, although limited samples were tested. Penicillium brocae, which may produce mutagenic metabolites, was isolated for the first time from the surface of Thai rice grains.

Antifungal Activity and Aflatoxin Degradation of Bifidobacterium Bifidum and Lactobacillus Fermentum Against Toxigenic Aspergillus Parasiticus.

Food and feedstuff contamination with aflatoxins (AFTs) is a serious health problem for humans and animals, especially in developing countries. The present study evaluated antifungal activities of two lactic acid bacteria (LAB) against growth and aflatoxin production of toxigenic Aspergillus parasiticus. The mycelial growth inhibition rate of A. parasiticus PTCC 5286 was investigated in the presence of Bifidobacterium bifidum PTCC 1644 and Lactobacillus fermentum PTCC 1744 by the pour plate method. After seven days incubation in yeast extract sucrose broth at 30°C, the mycelial mass was weighed after drying. The inhibitory activity of LAB metabolites against aflatoxin production by A. parasiticus was evaluated using HPLC method. B. bifidum and L. fermentum significantly reduced aflatoxin production and growth rate of A. parasiticus in comparison with the controls (p≤0.05). LAB reduced total aflatoxins and B1, B2, G1 and G2 fractions by more than 99%. Moreover, LAB metabolites reduced the level of standard AFB1, B2, G1 and G2 from 88.8% to 99.8% (p≤0.05). Based on these findings, B. bifidum and L. fermentum are recommended as suitable biocontrol agents against the growth and aflatoxin production by aflatoxigenic Aspergillus species.

A new in vitro method to detect growth and ochratoxin A-producing ability of multiple fungal species commonly found in food commodities

The aim of the study was to develop a new screening method to detect growth and ochratoxin A (OTA) production by multiple fungi growing in a small quantity of culture media, using microtiter plates.Eight ochratoxigenic species were included in the study. The strains were inoculated in sterile 96-well flat-bottom microtiter plates containing Yeast Extract Sucrose broth and Czapek Yeast Extract broth and incubated at 25 °C. Growth was daily monitored by absorbance measurements for 4 days and extended to 7 and 10 days for Penicillium spp. The entire experiment was repeated twice on different days. On each sampling time, five of the seven replicate wells inoculated for each strain and culture media were randomly selected and the content of each well was removed, extracted and injected into the HPLC. No statistically significant differences were observed for absorbance and OTA values, neither between replicates nor between experiments. Quantifiable OTA levels were detected after 48 h of incubation in Aspergillus alliaceus, Aspergillus carbonarius and Aspergillus niger, after 72 h in Aspergillus flocculosus, Aspergillus steynii and Aspergillus westerdijkiae and after 7 days in Penicillium nordicum and Penicillium verrucosum. The method offers the necessary tools for a rapid detection of growth and OTA production avoiding the use of plate cultures and can be very useful when many fungal isolates need to be screened.

Antifungal effect of eugenol and carvacrol against foodborne pathogens Aspergillus carbonarius and Penicillium roqueforti in improving safety of fresh-cut watermelon.

Background:Essential oil components eugenol and carvacrol (ranging between 100 and 200 ppm for carvacrol and between 250 and 750 ppm for eugenol) were tested for antifungal activity against foodborne pathogenic fungal species Aspergillus carbonarius A1102 and Penicillium roqueforti PTFKK29 in in vitro and in situ conditions.Materials and Methods:In vitro antifungal activity of eugenol and carvacrol was evaluated by macrobroth method, while watermelon Citrullus lanatus L. Sorento slices were used for antifungal assays in situ.Results:Selected components, eugenol and carvacrol showed significant inhibitory effect against tested fungi (A. carbonarius A1102 and P. roqueforti PTFKK29) in yeast extract sucrose broth, as well as in in situ conditions. The minimal inhibitory concentration (MIC) of eugenol against A. carbonarius A1102 determined by macrobroth method was 2000 ppm, while against P. roqueforti PTFKK29 determined MIC was 1000 ppm. Carvacrol inhibited growth of A. carbonarius A1102 at minimal concentration of 500 ppm, while against P. roqueforti PTFKK29, MIC was 250 ppm. The assays in real food system watermelon slices for eugenol and carvacrol show that the inhibitory effect against both selected fungal species was concentration dependent. Furthermore, our results showed that antifungal effect of carvacrol as well as eugenol applied on watermelon slices in all concentrations was a result of effective synergy between an active antifungal compound and lower incubation temperature (15°C) in inhibition of A. carbonarius A1102.Conclusion:The present study suggests that the use of eugenol and carvacrol is promising natural alternative to the use of food chemical preservatives, in order to improve safety and quality of fresh-cut and ready-to-eat fruits.

Inhibitory Effect of Clove (Syzygium aromaticum) on the Growth of Penicillium citrinum and Citrinin Production

AbstractClove was studied for its effect on the growth of Penicillium citrinum and citrinin production in culture medium and rice. The minimum concentration at which clove inhibited fungal growth and citrinin production was determined and recorded as 1.8 mg/mL in yeast extract sucrose broth. All concentrations of clove inhibited the fungal growth; however, citrinin production was inhibited significantly only at higher concentration. At 1.6 mg/mL, clove inhibited fungal growth and citrinin production by 80 and 58%, respectively; hence, this concentration was used to study the relationship between P. citrinum and citrinin production. Clove inhibited the growth of P. citrinum in culture media by 60–70%, throughout the observation period of 14 days. Along with the fungal growth inhibition, citrinin production was inhibited significantly. In rice, clove delayed the growth of Penicillium by 3 days; however, after 5 days of incubation, fungal growth and citrinin production were equivalent to the control.Practical ApplicationsCitrinin is a nephrotoxin and found as a common contaminant in rice, wheat and red yeast rice. This study showed the potential of clove in controlling P. citrinum and citrinin in culture media and rice. As spices are commonly used in many food ingredients, clove may be recommended for use in processed and ready‐to‐eat foods as a preservative. The use of whole clove eliminates the need for extracting essential oils and is more economical.

The potential effects of Zataria multiflora Boiss essential oil on growth, aflatoxin production and transcription of aflatoxin biosynthesis pathway genes of toxigenic Aspergillus parasiticus

This study aims at evaluating the effects of Zataria multiflora (Z. multiflora) essential oil (EO) on growth, aflatoxin production and transcription of aflatoxin biosynthesis pathway genes. Total RNAs of Aspergillus parasiticus (A.parasiticus) ATCC56775 grown in yeast extract sucrose (YES) broth medium treated with Z. multiflora EO were subjected to reverse transcription- polymerase chain reaction (RT-PCR). Specific primers of nor-1, ver-1, omt-A and aflR genes were used. In parallel mycelial dry weight of samples were measured and all the media were assayed by high-pressure liquid chromatography (HPLC) for aflatoxinB1 (AFB1), aflatoxinB2 (AFB2), aflatoxinG1 (AFG1), aflatoxinG2 (AFG2) and aflatoxin total (AFTotal) production. The results showed that mycelial dry weight and aflatoxin production reduce in the presence of Z. multiflora EO (100 ppm) on day 5 of growth. It was found that the expression of nor-1, ver-1, omt-A and aflR genes was correlated with the ability of fungus to produce aflatoxins on day 5 in YES medium. RT-PCR showed that in the presence of Z.multiflora EO (100 ppm) nor-1, ver-1 and omtA genes expression was reduced. It seems that toxin production inhibitory effects of Z. multiflora EO on day 5 may be at the transcription level and this herb may cause reduction in aflatoxin biosynthesis pathway genes activity.

Mycotoxin-Producing Ability and Chemotype Diversity of Aspergillus Section Flavi from Soils of Peanut-Growing Regions in Iran

Invasion of crops with Aspergillus flavus may result in contamination of food and feed with carcinogenic mycotoxins such as aflatoxins (AF) and cyclopiazonic acid (CPA). In the present study, distribution and toxigenicity of Aspergillus flavus and A. parasiticus in soils of five peanut fields located in Guilan province, Northern Iran was investigated. From a total of 30 soil samples, 53 strains were isolated which all of them were finally identified as A. flavus by a combination of colony morphology, microscopic criteria and mycotoxin profiles. Chromatographic analysis of fungal cultures on yeast extract sucrose broth by tip culture method showed that 45 of the 53 A. flavus isolates (84.9%) were able to produce either CPA or AFB1, while eight of the isolates (15.1%) were non-toxigenic. The amounts of CPA and AFB1 produced by the isolates were reported in the range of 18.2-403.8μg/g and 53.3-7446.3μg/g fungal dry weights, respectively. Chemotype classification of A. flavus isolates based on the ability for producing mycotoxins and sclerotia showed that 43.4% were producers of CPA, AFB1 and sclerotia (group I), 13.2% of CPA and AFB1 (group II), 9.4% of AFB1 and sclerotia (group III), 13.2% of AFB1 (group IV), 5.7% of CPA and sclerotia (group V) and 15.1% were non-toxigenic with no sclerotia (group VI). No strain was found as producer of only CPA or sclerotia. These results indicate different populations of mycotoxigenic A. flavus strains enable to produce hazardous amounts of AFB1 and CPA are present in peanuts field soils which can be quite important regard to their potential to contaminate peanuts as a main crop consumed in human and animal nutrition.

The inhibitory effect of oregano extract on the growth of Aspergillus spp. and on sterigmatocystin biosynthesis

The aim of this study was to investigate the effect of oregano extract on the growth of Aspergillus species (Aspergillus niger, Aspergillus carbonarius, and Aspergillus wentii) isolated from food and biosynthesis of sterigmatocystin (STC) by Aspergillus versicolor. Antifungal determinations were conducted using the agar plate method. The effect of oregano extract on the biosynthesis of STC was determined in a Yeast Extract Sucrose (YES) broth. The STC content and mycelial growth of A. versicolor were determined on the 7th, 14th, and 21st day with all applied concentrations of oregano extract and control sample. The composition of oregano extract was determined by gas chromatography–mass spectrometry (GC–MS) and 21 different components were identified. The major components were carvacrol (34.20%) and carvone (18.05%). At 2.5 mL/100 mL concentration, the oregano extract completely inhibited the growth of A. wentii, while the growth of A. carbonarius and A. niger was reduced by 95.6% and 45.6%, respectively. Significant reductions in STC biosynthesis during 21 days of incubation were observed for extract concentrations higher than 0.06 mL/100 mL. The obtained results showed that the tested oregano extract could be used as a food preservative to prevent food-borne fungal infections and mycotoxin production.

Effects of Onion (Allium cepa L.) and Garlic (Allium sativum L.) Essential Oils on the Aspergillus versicolor Growth and Sterigmatocystin Production

In the present study the effects of individual and combined essential oils (EOs) extracted from onion (Allium cepa L.) bulb and garlic (Allium sativum L.) clove on the growth of Aspergillus versicolor and sterigmatocystin (STC) production were investigated. The EOs obtained by hydrodistillation were analyzed by GC/MS. Twenty one compounds were identified in onion EO. The major components were: dimethyl-trisulfide (16.64%), methyl-propyl-trisulfide (14.21%), dietil-1,2,4-tritiolan (3R,5S-, 3S,5S- and 3R,5R- isomers) (13.71%), methyl-(1-propenyl)-disulfide (13.14%), and methyl-(1-propenyl)-trisulfide (13.02%). The major components of garlic EO were diallyl-trisulfide (33.55%), and diallyl-disulfide (28.05%). The mycelial growth and the STC production were recorded after 7, 14, and 21 d of the A. versicolor growth in Yeast extract sucrose (YES) broth containing different EOs concentrations. Compared to the garlic EO, the onion EO showed a stronger inhibitory effect on the A. versicolor mycelial growth and STC production. After a 21-d incubation of fungi 0.05 and 0.11 μg/mL of onion EO and 0.11 μg/mL of garlic EO completely inhibited the A. versicolor mycelial growth and mycotoxins biosynthesis. The combination of EOs of onion (75%) and garlic (25%) had a synergistic effect on growth inhibition of A. versicolor and STC production.

A survey on distribution and toxigenicity of Aspergillus flavus from indoor and outdoor hospital environments

In the present study, genetic diversity and mycotoxin profiles of Aspergillus flavus isolated from air (indoors and outdoors), levels (surfaces), and soils of five hospitals in Southwest Iran were examined. From a total of 146 Aspergillus colonies, 63 isolates were finally identified as A. flavus by a combination of colony morphology, microscopic criteria, and mycotoxin profiles. No Aspergillus parasiticus was isolated from examined samples. Chromatographic analyses of A. flavus isolates cultured on yeast extract-sucrose broth by tip culture method showed that approximately 10% and 45% of the isolates were able to produce aflatoxin B(1) (AFB(1)) and cyclopiazonic acid (CPA), respectively. Around 40% of the isolates produced sclerotia on Czapek-Dox agar. The isolates were classified into four chemotypes based on the ability to produce AF and CPA that majority of them (55.5%) belonged to chemotype IV comprising non-mycotoxigenic isolates. Random amplified polymorphic DNA (RAPD) profiles generated by a combination of four selected primers were used to assess genetic relatedness of 16 selected toxigenic and non-toxigenic isolates. The resulting dendrogram demonstrated the formation of two separate clusters for the A. flavus comprised both mycotoxigenic and non-toxigenic isolates in a random distribution. The obtained results in this study showed that RAPD profiling is a promising and efficient tool to determine intra-specific genetic variation among A. flavus populations from hospital environments. A. flavus isolates, either toxigenic or non-toxigenic, should be considered as potential threats for hospitalized patients due to their obvious role in the etiology of nosocomial aspergillosis.

Inhibition of ochratoxin A production of Aspergillus carbonarius by yeast species

A total of 21 yeast strains isolated from wine-grapes of Turkey were screened for their ability to inhibit ochratoxin A (OTA) accumulation by Aspergillus carbonarius in both yeast extract sucrose (YES) broth and grape juice. In monoculture, A. carbonarius produced a mean level of 39.03 &amp;micro;g/l and 21.32 &amp;micro;g/l OTA when grown in YES medium and grape juice, respectively. However, its ability to produce OTA in YES medium was greatly reduced in the presence of yeast strains except for Candida lusitaniae E2, Kloeckera spp. E4, and Rhodotorula glutinis D6. The percentage of inhibition of OTA production in YES medium ranged between 4.67% and 99.87%. Similarly, OTA production was inhibited in grape juice by more than 50% in the presence of yeast strains apart from Candida famata E6, R. glutinis, C. famata O3, Kloeckera spp. B3, and C. lusitaniae D9. The present study highlights the potential use of yeast isolates in the biocontrol of ochratoxin A-producing A. carbonarius.