Aflatoxin B1 Accumulation Research Articles

Vitamin C가 방사선과 Aflatoxin B1을 처리한 흰쥐의 간세포에서 Aflatoxin B1-DNA Adduct 형성에 미치는 영향

The objective of this study was to examine the effects of vitamin C on the formation of aflatoxin B1 (AFB1)-DNA adduct and AFB1-induing cellular oxidative damage in rat livers treated with radiation and AFB1. Six-week-old male Sprague-Dawley rats were randomly divided into five groups: the control group, the AFB1-treated group, the group treated with AFB1 and vitamin C, the group treated with X-ray and AFB1, and the group treated with X-ray and AFB1 with vitamin C. On the first day of the experiment, only one dose of X-rays was exposed to the entire liver at 1,500 cGy. Next, vitamin C was injected at 10 mg/kg body weight via intraperitoneal injection, followed an hour later by the administration of 0.4 mg/kg of AFB1 via intraperitoneal injection. These treatments were administered every three days for 15 days. On the 16th day, the animals were sacrificed. The AFB1 contents of the rat sera were determined via indirect competitive ELISA. In the quantitative analysis of AFB1 in the rat sera via ELISA, 5.17±0.34 ng/mL of AFB1 was detected in the AFB1-treated groups, but the amount decreased more significantly to 3.23±0.76 ng/mL in the groups treated with AFB1 and vitamin C (p<0.01) than in the AFB1-treated groups. The effect of vitamin C on AFB1-DNA adduct formation was determined via ELISA. The values of AFB1-DNA adduct formation were 9.38±0.41 ng/ml in the AFB1-treated groups, but the amount decreased more significantly to 5.28±0.32 ng/mL in the groups treated with AFB1 and vitamin C (p<0.01) than in the AFB1-treated groups. Immunohistochemistry revealed that the accumulation of the AFB₁was not observed in the normal liver tissue (G1). The AFB1-positive materials were observed in the central vein and the portal vein of the liver tissue from the AFB1 (G2) treatment or the X-ray and AFB1 (G4) co-treatment, but the AFB1-positive materials were observed weakly in the group treated with vitamin C (G3 and G5). These results indicate that vitamin C had ameliorating effects on the AFB1 accumulation of liver tissue.

Antifungal and antiaflatoxigenic activity by vapor contact of three essential oils, and effects of environmental factors on their efficacy

The present investigation reports the antifungal and antiaflatoxigenic properties of essential oils (EOs) from boldo (Pëumus boldus Mol.), poleo (Lippia turbinata var. integrifolia Griseb., clove (Syzygium aromaticum L.) and from boldo and poleo mixtures present in the headspace of peanut extract medium at three water activity levels (aW) (0.98, 0.95 and 0.93). Moreover, the ability of boldo and poleo oils to maintain their antifungal activity was evaluated after subjecting them to environmental variations. Boldo EO at doses ≥1500 μL/L showed a highly significant effect on Aspergillus section Flavi lag phase (>300 h), growth rate (93–100% of inhibition) and aflatoxin B1 (AFB1) accumulation (100% of inhibition) at all aW levels assayed. The antifungal and antiaflatoxigenic effects of poleo and clove EOs were highly dependent on aW. In general boldo–poleo oil mixtures showed less inhibitory activity on Aspergillus strains than the boldo pure oil. The antifungal ability of volatile components released by boldo and poleo EOs was stable against temperature changes; while it was reduced when poleo was stored during six months and when boldo was exposed to sunlight and UV.Boldo and poleo EO volatile fractions can be used as effective non-toxic biopreservatives in stored peanut industry against AF contamination.

Growth and aflatoxin B1 accumulation of gibel carp adult fed with diets of different levels of aflatoxin B1

Growth and aflatoxin B1 accumulation of gibel carp adult fed with diets of different levels of aflatoxin B1

Invitro evaluation of five essential oils as botanical fungitoxicants for the protection of stored peanuts from Aspergillus flavus and A. parasiticus contamination

The antifungal potential of five plant-derived essential oils (EOs) (boldo [Pëumus boldus Mol.], poleo [Lippia turbinata var. integrifolia (Griseb.)], clove [Syzygium aromaticum L.], anise [Pimpinella anisum], and thyme [Thymus vulgaris]) was evaluated against aflatoxigenic Aspergillus strains on peanut-based medium conditioned at different water activity (aW) levels (0.98, 0.95, 0.93). Effects of EOs added to the peanut meal extract agar on the lag phase, growth rate, and aflatoxin B1 (AFB1) accumulation by Aspergillus flavus and A. parasiticus were evaluated. The five EOs analyzed have been shown to influence lag phase, growth rate, and AFB1 accumulation. Although the low dose (500 ppm) of boldo, poleo, and clove showed no significant effects on lag phase (range of increase = 0–75%) and growth rate (range of reduction = 0–65%), the application of high concentrations of these EOs (2500 μl l−1 for boldo and poleo and 1500 μl l−1 for clove) completely inhibited growth of Aspergillus species, regardless of aqueous medium availability. The anti-aflatoxigenic property of boldo and poleo EOs (500 μl l−1) was more marked with the medium aW reduction; inhibition percentages were estimated at 75, 83, and 100% at 0.98, 0.95, and 0.93 aW, respectively.These findings support the application of boldo, poleo, and clove EOs for surface treatment and leave open the possibility of using them as vapor exposure to prevent mold contamination in stored peanut.

Influence of sub-lethal antioxidant doses, water potential and temperature on growth, sclerotia, aflatoxins and aflD (=nor-1) expression by Aspergillus flavus RCP08108

Effects of interacting conditions of sub-lethal levels of antioxidants, water potential (Ψ) and temperature were evaluated on growth, sclerotial characteristics, aflatoxin B1 (AFB1) production and aflD (=nor-1) gene expression by Aspergillus flavus strain RCP08108. These studies were carried out on peanut meal extract agar osmotically modified to −2.8,−7.1, −9.9 and −16.0MPa and incubated at 28 and 20°C. The food grade antioxidants added were butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) at (1+1mM−M1) and (5+5mM−M2). To relate the aflD expression after toxigenic A. flavus grew under interacting stress conditions, real-time PCR was used. Antioxidant mixtures caused a higher and significant (p<0.001) reduction in growth rate. The major impact on size and volume sclerotia was produced by Ψ; followed by antioxidant mixtures. High AFB1 levels were observed in response to the M1 applied at −7.1MPa. Induction of the aflD gene was observed in response to the M1 treatment at −2.8, −7.1 and −9.9MPa; but significant decreases of AFB1 production and aflD transcripts were observed; when the fungus grew in the presence of the M2 treatment.These results showed that it is necessary to apply food-grade antioxidants into the peanut storage system at levels higher than 5mM. This is an important tool to avoid sub-lethal antioxidant doses that can lead to fungal growth, increase resistance structures, and stimulate aflD gene expression and AFB1 accumulation in this substrate.

Impact of a Streptomyces (AS1) strain and its metabolites on control of Aspergillus flavus and aflatoxin B1 contamination in vitro and in stored peanuts

Six actinomycetes were isolated from peanuts in Egypt. Of these, a Streptomyces strain (AS1) was found in in vitro assays to inhibit directly or via secondary metabolites both germination and growth of Aspergillus flavus. Tests of the AS1 cells for direct control of A. flavus populations or aflatoxin B1 (AFB1) production on stored peanuts was unsuccessful over 14-day storage periods. However, crude extracts of AS1 metabolites at 50 and 100 ppm completely inhibited spore germination of conidia of A. flavus in vitro over 48 h. Comparison of solvents for extracting the metabolites showed that the ethyl acetate extract was most effective. This gave greater than 85% inhibition of mycelial growth at these concentrations at different water availabilities (water activity; a w; 0.95, 0.92, and 0.89) and 25°C. Doses of 50, 200, and 500 ppm of AS1 metabolites significantly inhibited populations of A. flavus on stored peanuts at two water stress levels (0.90, 0.93 a w) at 25°C over 14-day storage periods. The amounts of AFB1 produced by A. flavus on peanuts stored at 0.90 a w were significantly decreased by AS1 metabolites for only 7 days. However, at 0.93 a w doses of 200 and 500 ppm significantly controlled AFB1 accumulation in peanuts for 14 days.

English

&nbsp; Previous work indicated that some of the new synthesized analogues of dehydroacetic acid (DHA) were inhibitory to the growth of mycotoxin producing moulds and accumulation of aflatoxin B1&nbsp;(AFB1) and ochratoxin A (OTA). The objective of this study was to determine the specific new synthesized chemical compounds that may be effective against mould growth and vomitoxin (deoxynivalenol) (DON) accumulation by&nbsp;Fusarium graminearum. The effect of the investigated 3-/2-aminophenylamine-(p-toluoyl)-4-hydroxy-6-(p-tolyl)-2H-pyrane-2-one (Schiff base) and 4-hydroxy-3-(p-toluoyl)-6-(p-tolil)-2H-pyrane-2-one (DHT) on growth and DON accumulation were studied using a mould&nbsp;F. graminearumZMPBF 1244 and maize grain hybrid to determine the possible use of these compounds as a mean of controlling DON accumulation. Schiff base was inhibitory at 0.05 and 0.1 &micro;g/g and DHT at 0.5 &micro;g/g of maize grain. The inhibitory effect of these substances was judged to be the inhibition of growth rather than toxin accumulation. When growth&nbsp;occurred&nbsp;after a delay, DON accumulation occurred when the cultures reached secondary metabolism. Given sufficient time, cultures which were inhibited initially, but which subsequently inhibited their growth, produced toxin levels equivalent to the control cultures. Levels of the Schiff base above 0.2 &micro;g/g almost completely inhibited mould growth or permitted only a small amount of growth that never reached secondary metabolism and never produced DON during the time of this study. &nbsp; Key words:&nbsp;Fusarium graminearum, vomitoxin, Schiff base, chitin,&nbsp;Artemia salina.

Low levels of Aflatoxin B1 could cause mortalities in juvenile hybrid sturgeon, Acipenser ruthenus ♂×A. baeri♀

Toxicity of aflatoxin B1 (AFB1) was investigated in juvenile hybrid sturgeon Acipenser ruthenus ♂ × A. baeri♀, an important coldwater finfish farmed in China and other countries. Seven experimental diets (Diet A–G) containing different levels of AFB1 (0, 1, 5, 10, 20, 40 and 80 μg kg−1 diet) were fed to juvenile sturgeon weighing 10.53 ± 0.17 g kg−1 to determine its effect on survival, growth, feed consumption, hematocrit, liver histology as well as muscular and hepatic toxin accumulation. The experiment lasted for 35 days and was conducted in two periods of 25 and 10 days each. No external changes or unusual behaviour was observed in the fish fed diets with AFB1. Mortality was observed in fish fed with highest levels of AFB1 (80 μg kg−1– Diet G) from day 12 onwards. After 25 days, fish fed the diet of 80 μg AFB1 kg−1 showed significant lower survival (50 ± 5.77%) followed by those fed 40 μg AFB1 kg−1 diet (80 ± 5.77%) and 20 μg AFB1 kg−1 diet (86.66 ± 3.33%). No significant difference was observed in specific growth rate (SGR) or hepatosomatic index (HSI) between groups. Hematocrit was significantly higher in the fish fed the diet of highest AFB1. The fish were weighed at day 25 in some treatments (Diets F and G) because of high mortality. However, feeding was continued for another 10 days to observe mortality or behavioural changes if any in the other groups. After 35 days, survival in the fish fed Diet F (40 μg AFB1 kg−1) was 40% and those fed Diet E (20 μg AFB1 kg−1) was 36.2%. Significant histopathological changes including nuclear hypertrophy, hyperchromasia, extensive biliary hyperplasia, focal hepatocyte necrosis and presence of inflammatory cells were observed in the liver of fish fed high levels of aflatoxin (40 and 80 μg kg−1). AFB1 accumulation in fish muscle and liver increased with increased dietary AFB1 levels. It could be confirmed that 10 μg AFB1 kg−1 diet was the maximum allowable level in hybrid sturgeon diet.

Potential of aflatoxin B1 production by Aspergillus flavus strains on commercially important food grains

In this study, we investigated the potential of aflatoxin B1 (AFB1) production by five Aspergillus flavus strains previously isolated from sorghum grains on cereals (barley, maize, rice, wheat and sorghum), oilseeds (peanuts and sesame) and pulses (greengram and horsegram). Five strains of A. flavus were inoculated on all food grains and incubated at 25 °C for 7 days; AFB1 was extracted and estimated by enzyme-linked immunosorbent assay. All A. flavus strains produced AFB1 on all food grains ranging from 245.4 to 15 645.2 μg kg−1. Of the five strains tested, strain Af 003 produced the highest amount of AFB1 on all commodities ranging from 2245.2 to 15 645.2 μg kg−1. Comparatively, the AFB1 accumulation was high on rice grains ranging from 3125.2 to 15 645.2 μg kg−1, followed by peanuts ranging from 2206.2 to 12 466.5 μg kg−1. Less AFB1 accumulation was observed in greengram and sesame seeds ranging from 645.8 to 2245.2 and 245.4 to 2890.6 μg kg−1, respectively. Our results showed that all food grains tested are susceptible to A. flavus growth and subsequent AFB1 production.

Varietal differences in accumulation of aflatoxin B1 in Indian rice cultivars

Rice (paddy) seeds are known to be colonised by Aspergillus flavus in the field or under storage conditions and contaminated with aflatoxins which have impact on human and animal health. In this study, we investigated the varietal differences in 30 Indian healthy rice cultivars used for human consumption (15 normal and 15 basmati) for accumulation of aflatoxin B1 (AFB1) after inoculation with aflatoxin-producing A. flavus (DRAf 009). Significant varietal differences in AFB1 accumulation were observed in normal and basmati rice cultivars. Comparatively, the accumulation of AFB1 is higher in normal cultivars, ranging from 3-628 µg/kg, than in basmati cultivars, ranging from 0.2-7.2 µg/kg. The highest accumulation of AFB1 in normal cultivars was observed in PR 106 (628 µg/kg) and the lowest in IR 64 (3 µg/kg). In basmati rice cultivars, the highest accumulation of AFB1 was observed in Ranbir basmati (7.2 µg/kg) and the lowest in Vasumati (0.2 µg/kg). All these cultivars were evaluated for their total phenolic content (TPC) in rice bran using the Folin-Ciocalteau method. The results indicated that the TPC of normal and basmati cultivars was in the range of 1.96-2.45 and 2.13-2.65 mg gallic acid equivalent (mg/g of bran), respectively. This study may be used as a basis to develop A. flavus resistant rice cultivars and proper storage structures to produce aflatoxin-free rice. This is the first report on the evaluation of various rice cultivars for accumulation of AFB1 after inoculation with A. flavus.

Natural maize phytochemicals for control of maize mycoflora and aflatoxigenic fungi

This research was undertaken to evaluate the effects of the natural phytochemicals trans-cinnamic acid (CA) alone at concentrations of 20 and 25 mM, ferulic acid (FA) at concentration of 30 mM and two mixtures, CA-FA (20+30 mM) and CA-FA (25+30 mM) on natural maize mycoflora, Aspergillus section Flavi population and aflatoxin B1 production. These studies were carried out in maize grain in relation to a water activity of 0.99, 0.97 and 0.94. CA at 25 mM and the mixture CA-FA (25+30 mM) were the most effective treatments at inhibiting natural maize mycoflora at all aw assayed after 11 and 35 days of incubation at 25 °C. In general, 20 mM CA caused complete inhibition of Aspergillus section Flavi population at all aw values tested during all incubation period without an additional inoculum. 20 mM CA and 25 mM CA showed the major inhibitory effect on aflatoxin B1 accumulation of control and Aspergillus section Flavi additionally inoculated during all incubation periods. The data showed that CA and FA could be considered as effective fungitoxicants for natural maize mycoflora and aflatoxigenic fungi in the aw range 0.99 to 0.94. The information obtained shows promise for controlling aflatoxigenic fungi in stored maize.

Evidence that a wortmannin-sensitive signal transduction pathway regulates aflatoxin biosynthesis

A signal transduction pathway involving cAMP and protein kinase A (PKA) regulates aflatoxin accumulation and nor-1 and ver-1 (aflatoxin structural genes) promoter function in Aspergillus parasiticus by modulating expression of a key transcriptional activator, AflR. To understand the function of this pathway in greater detail we treated A. parasiticus in culture with wortmannin, a frequently used probe of phosphatidyl inositol (PI)-3 kinase activity. A. parasiticus D8D3 (nor-1::GUS reporter) and I4 (ver-1::GUS reporter) were grown on a defined solid growth medium (GMS agar) under aflatoxin-inducing conditions. GMS containing wortmannin (1 microM) reduced aflatoxin B1 accumulation up to 15-fold accompanied by a similarly large decrease in ver-1 and nor-1 promoter activity. Wortmannin inhibited growth (colony diameter) and asexual sporulation but to a much smaller extent. Wortmannin treatment increased intracellular cAMP levels up to 25-fold; total PKA activity also increased within 10 min of wortmannin exposure. These data support a regulatory model in which PI-3 kinase activity modulates intracellular cAMP accumulation and PKA activity. This in turn regulates AflR expression and activity, aflatoxin gene expression and aflatoxin accumulation.

Evidence that a wortmannin-sensitive signal transduction pathway regulates aflatoxin biosynthesis

A signal transduction pathway involving cAMP and protein kinase A (PKA) regulates aflatoxin accumulation and nor-1 and ver-1 (aflatoxin structural genes) promoter function in Aspergillus parasiticus by modulating expression of a key transcriptional activator, AflR. To understand the function of this pathway in greater detail we treated A. parasiticus in culture with wortmannin, a frequently used probe of phosphatidyl inositol (PI)-3 kinase activity. A. parasiticus D8D3 (nor-1::GUS reporter) and I4 (ver- ::GUS reporter) were grown on a defined solid growth medium (GMS agar) under aflatoxin-inducing conditions. GMS containing wortmannin (1 μM) reduced aflatoxin B1 accumulation up to 15-fold accompanied by a similarly large decrease in ver-1 and nor-1 promoter activity. Wortmannin inhibited growth (colony diameter) and asexual sporulation but to a much smaller extent. Wortmannin treatment increased intracellular cAMP levels up to 25-fold; total PKA activity also increased within 10 min of wortmannin exposure. These data support a regulatory model in which PI-3 kinase activity modulates intracellular cAMP accumulation and PKA activity. This in turn regulates AflR expression and activity, aflatoxin gene expression and aflatoxin accumulation.

Potential use of phenolic antioxidants on peanut to control growth and aflatoxin B1 accumulation by Aspergillus flavus and Aspergillus parasiticus

AbstractFood‐grade antioxidants: butylated hydroxyanisole (BHA), propyl paraben (PP) and butylated hydroxytoluene (BHT) (10 and 20 mmol g−1) and all the mixtures of these chemicals were tested for inhibitory activity on the growth of and aflatoxin B1 (AFB1) accumulation by Aspergillus parasiticus and A. flavus on irradiated (7 kGy) peanut grains. Also, the influence of these treatments was evaluated in different water conditions (0.982, 0.955, 0.937aw) at 11 and 35 days of incubation at 28 °C. Water activity (aw) affected the fungal growth, no fungal development was observed at the highest stress water condition (0.937aw). Butylated hydroxyanisole at 10 mmol g−1 level and all the mixtures with PP and/or BHT were significantly effective (P = 0.05) in increasing lag phase and reducing growth rate and colony forming units per gram of peanut of both Aspergillus section Flavi strains and AFB1 accumulation. The application of BHA at concentrations of 20 mmol g−1 alone or with PP and/or BHT totally inhibited fungal growth at 11 and 35 days of incubation. The results suggest that the addition of these chemical mixtures on peanut grains at low levels has potential to impact synergically on the control of Aspergillus section Flavi. Copyright © 2007 Society of Chemical Industry

Impact on growth and aflatoxin B1 accumulation by Kluyveromyces isolates at different water activity conditions

This study showed the impact on germination, mycelial growth and aflatoxin B(1) accumulation when interacting Aspergillus aflatoxigenic strains with Kluyveromyces isolates and the effect of water activity on this relationship. Isolates Y(14) and Y(16) reduced the percentage of germination of all Aspergillus strains and decrease germ tube elongation rate at majority of water activity assayed. Similarly they produced an increase of germination lag phase and lag phase of growth beside decreased growth rate of all Aspergillus strains. At water activities 0.994, 0.982, 0.955 and 0.937, no aflatoxins were produced in paired cultures with isolates Y(25,) Y(22), Y(16), and Y(14), and Kluyveromyces isolates Y(14) and Y(16) impact both growth and aflatoxin accumulation at wide range of water activity.

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

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). 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. 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). 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.

In vitro Selection of Maize Rhizobacteria to Study Potential Biological Control of Aspergillus Section Flavi and Aflatoxin Production

The aims of this study were to select bacterial isolates from the non-rhizophere of maize soil and to examine their antagonistic activity against Aspergillus section Flavi strains. The first selection was made through ecophysiological responses of bacterial isolates to water activity (a w) and temperature stress. Subsequently, an Index of Dominance test (I D), ecological similarity and inhibition of the lag phase prior to growth, growth rate and aflatoxin B1 accumulation were used as criteria. From the first assay nine bacterial strains were selected. They grew well at 25 and 30 °C, with growth optima between 0.982 and 0.955 a W using 48 h of incubation. There was ecological similarity between the bacterial strains Bacillus subtilis (RCB 3, RCB 6), Pseudomonas solanacearum RCB 5, Amphibacillus xylanus RCB 27 and aflatoxigenic Aspergillus section Flavi strains at 0.982 at 25 °C. The predominant interaction between all selected bacteria and fungi in dual culture was mutual intermingling at 0.982. Mutual inhibition on contact and mutual inhibition at a distance was observed at 0.955 a w, between only four bacteria and some Aspergillus strains. Bacillus subtilis RCB 55 showed antifungal activity against Aspergillus section Flavi strains. Amphibacillus xylanus RCB 27, B.␣subtilis RCB 90 and Sporolactobacillus inulinus RCB 196 increased the lag phase prior to growth and decreased the growth rate of Aspergillus section Flavi strains. Bacillus subtilis strains (RCB 6, RCB 55, RCB 90) and P. solanacearum RCB 110 inhibited aflatoxin accumulation. Bacillus subtilis RCB 90 completely inhibited aflatoxin B1 accumulation at 0.982 a W. These results show that the bacterial strains selected have potential for controlling Aspergillus section Flavi over a wide range of relevant environmental conditions in the stored maize ecosystem.

In vitro effect of phenolic antioxidants on germination, growth and aflatoxin B1 accumulation by peanut Aspergillus section Flavi

The effectiveness of the food-grade antioxidants butylated hydroxytoluene (BHT), trihydroxybutyrophenone (THB), propyl paraben (PP) and butylated hydroxyanisole (BHA) at 1, 10 and 20 mmol l(-1) concentrations on germination, growth, and aflatoxin B(1) (AFB(1)) production by Aspergillus section Flavi strains was determined. Assays on the lag phase of germination, germination percentage, germ tube elongation rate, lag phase, growth rate and AFB(1) production by three strains of Aspergillus flavus and three of Aspergillus parasiticus were carried out in vitro on peanut extract meal agar conditioned at different water activities (a(w): 0.982, 0.971, 0.955, 0.937). The antioxidants PP and BHA efficiently inhibited the germination of the two species tested at the doses 10 and 20 mmol(-1). The antioxidants PP and BHA at 1 mmol l(-1) and THB at 20 mmol l(-1) reduced the germ tube elongation rate most effectively, regardless of a(w) levels. An increase in the lag time and a reduction in the growth rate of 100% of the strains was observed, this was due to the action of BHT at the doses 10 and 20 mmol(-1) at 0.982, 0.971 and 0.955 a(w), although these treatments stimulated the AFB(1) accumulation in most of the fungi tested. The more effective antioxidants were PP and BHA, which increased the lag phase, reduced the growth rate and AFB(1) production in all of the strains at the four a(w) assayed. At concentrations 10 and 20 mmol l(-1), these antioxidants totally inhibited fungal development. The study shows that the antioxidants BHA and PP are effective fungal inhibitors to peanut Aspergillus section Flavi in wide range of water activity. The results suggest that phenolic antioxidants, BHA and PP, can be effective fungitoxicants on aflatoxigenic strains in peanut at industrial level.

In vitro studies on the potential for biological control on Aspergillus section Flavi by Kluyveromyces spp.

Antagonist activity of Kluyveromyces spp. isolates on Aspergillus section Flavi was studied. The screening of isolates were made through studies of growth at different water activities and temperatures, index of dominance (I(D)), ecological similarity, antifungal activity and impact on aflatoxin B1 accumulation. High optical density was obtained at 25 and 30 degrees C and 48 h of incubation. Cell growth decreases with decrease in water activity. The predominant interaction was mutual intermingling at a(w) = 0.982 and 0.955, while at a(w) = 0.999 and 0.937 mutual inhibition for contact was exhibited. All isolates were catabolically identical to Aspergillus section Flavi and compete by nutritional source. At high water activities yeasts showed inhibitory activity on Aspergillus strains, inhibition percentages varied between 75 and 100%. The isolates Y9, Y14, Y16, Y22, Y25 and Y33 showed antifungal activity and inhibitory activity on aflatoxin B1 accumulation at all water activities assayed from all Aspergillus section Flavi strains. The data show that the isolates selected in a wide range of environmental conditions could exert their roll like biological control agents for Aspergillus section Flavi in storage maize ecosystem. Isolates of Kluyveromyces spp. may have practical value in the postharvest control of storage maize.

Impact of environment and interactions of Fusarium verticillioides and Fusarium proliferatum with Aspergillus parasiticus on fumonisin B1 and aflatoxins on maize grain

AbstractFusarium verticillioides and F proliferatum isolates were inoculated in mixed cultures with Aspergillus parasiticus on irradiated maize grain at two different inoculum concentrations (2 × 105 and 2 × 102 conidia g−1 dry maize). The treatments were 0.93–0.98 water activity (aw) and 15 and 25 °C for 28 days. A complex relationship was found between aw, temperature, inoculum concentration and the interactions which took place between fumonisin and aflatoxin producers. In general, A parasiticus reduced F verticillioides and F proliferatum populations (by 6–36%) but did not affect fumonisin B1 production by these species. In contrast, while the Fusarium species were not able to decrease A parasiticus populations, they significantly reduced aflatoxin B1 accumulation (by 30–93%).© 2001 Society of Chemical Industry