Strains Of Aspergillus Flavus Research Articles

Gamma irradiation of Aspergillus flavus strains associated with Indonesian nutmeg (Myristica fragrans).

The aims of this work were to investigate the effects of gamma irradiation on population, viability and aflatoxin B1 production of Aspergillus flavus strains isolated from nutmeg kernels. Thirteen strains of A. flavus were isolated and cultured in potato dextrose agar. Conidia were harvested, air-dried, and irradiated 0, 5, or 10kGy with gamma rays using a Cobalt-60 source. Toxigenicity were determined using a coconut agar medium and thin layer chromatography. Genomes of strains were extracted from mycelia. Four sets of primers, regulatory (aflR) and structural genes (nor-1, ver-1, omt-1) were used to confirm the presence of the genes. Our results indicate that total fungal populations decreased significantly (P<0.05) with increasing irradiation dose. However, doses of 5 and 10kGy were insufficient to completely eliminate the viability of some A. flavus strains. Irradiation did not change toxigenicity and triggered surviving toxigenic strains to produce aflatoxin B1.

Antimicrobial activity and Identification of fungus associated Stylissa flabelliformis sponge collected from Menjangan Island West Bali National Park, Indonesia

The Fungus is a very important microorganism as a producer of bioactive secondary metabolites. Active substances of microbial origin have been sought through the process of screening methods to obtain antimicrobial compounds. The purpose of this study was to isolate fungi associated with sponge taken from Menjangan Island National Park West Bali (Indonesia) and identify fungi that have antimicrobial activity. Isolation of fungus from sponge was carried out by spread plate method using Saboroud Saline Agar medium. Each fungi will be tested to Staphylococcus aureus ATCC 29213, Escherichia coli ATCC 25922 and Candida albicans ATCC 10231. Identification of fungi is based on the observation of macroscopic, microscopic and also using 16rRNA/ITS phylogeny tree. The results showed that S. flabelliformis sponge had 10 fungal isolates. Most of them have antimicrobial activity. The name associated with a sponge fungus is These 10 fungus are Aspergillus flavus strain UPMZ02, Aspergillus fumigatus strain CD1621, Trichoderma reesei strain JCM 2267, Aspergillus nomius strain KUB105, Aspergillus sp. strain TLWK-09, Aspergillus flavus strain MC-10-L, Penicillium sp. strain RMA-2, Aspergillus sp. strain TLWK-09, Aspergillus fumigatus and Trichoderma reesei strain TV221

In vitro antifungal susceptibility of clinical and environmental isolates of Aspergillus fumigatus and Aspergillus flavus in Brazil

The in vitro susceptibility of 105 clinical and environmental strains of Aspergillus fumigatus and Aspergillus flavus to antifungal drugs, such as amphotericin B, azoles, and echinocandins was evaluated by the broth microdilution method proposed by the European Committee on Antimicrobial Susceptibility Testing (EUCAST). Following the EUCAST-proposed breakpoints, 20% and 25% of the clinical and environmental isolates of A. fumigatus, respectively, were found to be resistant to itraconazole (Minimal Inhibitory Concentration, MIC>2.0mg/L). Voriconazole showed good activity against A. fumigatus and A. flavus strains, except for one clinical strain of A. fumigatus whose MIC was 4.0mg/L. Posaconazole (≤0.25mg/L) also showed appreciable activity against both species of Aspergillus, except for six A. fumigatus strains with relatively higher MICs (0.5mg/L). The MICs for Amphotericin B ranged from 0.06 to 1.0mg/L for A. fumigatus, but were much higher (0.5–8.0mg/L) for A. flavus. Among the echinocandins, caspofungin showed a geometric mean of 0.078 and 0.113 against the clinical and environmental strains of A. flavus, respectively, but had elevated minimal effective concentrations (MECs) for seven of the A. fumigatus strains. Anidulafungin and micafungin exhibited considerable activity against both A. fumigatus and A. flavus isolates, except for one environmental isolate of A. fumigatus that showed an MEC of 1mg/L to micafungin. Our study proposes that a detailed investigation of the antifungal susceptibility of the genus Aspergillus from different regions of Brazil is necessary for establishing a response profile against the different classes of antifungal agents used in the treatment of aspergillosis.

Detoxification of Aflatoxin B1 by Antifungal Compounds from Lactobacillus brevis and Lactobacillus paracasei, Isolated from Dairy Products.

Aflatoxins are a large group of highly toxic, mutagenic, and carcinogenic mycotoxins produced by specific species of fungi. Potential contamination of food commodities by these compounds causes extensive damage that lead to great economic losses. This study explored the potential use of antifungal compounds, produced by Lactobacillus brevis and Lactobacillus paracasei, for growth inhibition and subsequent aflatoxin B1 production from select strains of Aspergillus flavus and Aspergillus parasiticus. Lactobacilli strains were isolated from traditional Egyptian dairy products, whereas fungal strains were isolated from infected cereal seeds. There were noticeable decreases in mycelium biomass and aflatoxin production as well. L. brevis exhibited the highest reduction of aflatoxin B1 production by A. flavus and A. parasiticus, 96.31 and 90.43%, respectively. The concentrations of amino acids of the antifungal compound produced by L. brevis were significantly higher than that produced by L. paracasei. Asparagine, glutamine, glycine, alanine, and leucine were the most concentrated amino acids for both strains. The antifungal compounds produced by L. brevis and L. paracasei were active in a wide range of pH, heat stable and inactivated by proteolytic enzymes (protease K and trypsin A). The expression of Omt-A gene that involved in the later step of aflatoxin production was evaluated by real-time PCR. There was a vigorous reduction at transcriptional level of Omt-A gene observed in A. flavus that is treated by L. brevis and L. paracasei (80 and 70%, respectively). However, the reduction of Omt-A gene observed in A. parasiticus that is treated by L. brevis and L. paracasei was 64.5 and 52%, respectively. Treating maize seeds with antifungal compounds exhibited great efficiency in controlling fungal infection and increasing seed germination. The results confirmed that lactic acid bacteria are a promising strategy to control food contamination of fermented food and dairy products.

Nanoencapsulated Illicium verum Hook.f. essential oil as an effective novel plant-based preservative against aflatoxin B1 production and free radical generation

The study reports efficacy of Illicium verum essential oil (IvEO) against food borne moudls and its nanoencapsulation for enhancing antifungal and antiaflatoxigenic potency. Chemical characterization of the IvEO showed anethole (89.12%) as major compound followed by estragole (4.859%). The IvEO showed broad fungitoxic spectrum against common food borne moulds. It's minimum inhibitory concentration (MIC) and minimum aflatoxin B1 inhibitory concentration (MAIC) against aflatoxigenic strain Aspergillus flavus LHP-PV-1 were 0.7, and 0.5 μL/mL respectively. Morphological observations of treatment sets by SEM and TEM along with decrease in ergosterol content and enhanced leakage of Ca2+, K+ and Mg2+ ions denoted fungal cell membrane as site of action. The IvEO showed promising free radical scavenging activity and favourable safety profile with high LD50 value on mice. The IvEO also exhibited considerable protection of Pistacia vera from fungal contamination and complete protection from aflatoxin B1 contamination in storage containers. Nanoencapsulated IvEO in gel form and lyophilized form exhibited enhanced efficacy as fungal inhibitor and aflatoxin suppressor. The chemically characterised IvEO may be recommended as plant based preservative having favourable safety and its nanocapsules may be of industrial significance as shelf life enhancer of food items. This is the first report on in situ antiaflatoxigenic efficacy and nanoencapsulation of IvEO.

Genome Sequences of Three Strains of Aspergillus flavus for the Biological Control of Aflatoxin.

ABSTRACTAflatoxin is a carcinogenic contaminant of many commodities that are infected by Aspergillus flavus. Nonaflatoxigenic strains of A. flavus have been utilized as biological control agents. Here, we report the genome sequences from three biocontrol strains. This information will be useful in developing markers for postrelease monitoring of these fungi.

Agricultural potential of rhizospheric Bacillus subtilis strains exhibiting varied efficiency of surfactin production

Six Bacillus subtilis strains collected from broad-leaved trees rhizosphere and exhibiting an ability of surfactin production were investigated as potent plant biofertilizers with biocontrol activity. Lipopeptide (LP) biosurfactants were extracted by a modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) procedure proposed as a quick and effective method of isolating LP biosurfactants. Matrix-assisted laser desorption ionization time-of-flight tandem mass spectrometry (MALDI-TOF-TOF) was applied to detect the lipopeptides. Predominant peaks at m/z 1016, 1030, 1044, 1058 and 1072 were putatively assigned as surfactin Na adducts possess a Glu-Leu-Leu-Val-Asp-Leu–Leu peptide and the β-OH fatty acid with a different length (C13-C16) whereas m/z 1016 was C13 surfactin Na adduct with Val in position 7 on the peptide moiety. Four other ions m/z 1051, 1065, 1079 and 1093 were recognized as iturin A Na adducts. Five fengycin homologues with Na adducts (m/z 1471, 1485, 1499, 1513 and 1527) were also determined. The quantitative analyses of the compounds were performed with the use of liquid chromatography-mass spectrometry (LC–MS/MS). Strains IM 7, IM 16 and IM 17 cultivated in Luria-Bertani medium for 48h produced surfactin alone at the concentrations below 10mgl−1. In contrast, strains KP7, IM 13 and IM 14 produced surfactin much more efficiently. Surfactin concentrations in 72-h-old cultures reached 100.3, 55.3 and 124.4mgl−1, respectively and were accompanied by the production of iturin in concentrations 5.7, 142.5 and 2.3mgl−1, respectively. Additionally, in Cooper’s medium, strain KP7 increased twofold the production of surfactin and iturin. Only surfactin overproducers (KP7, IM 13 and IM 14) exhibited swarming motility and formed biofilms, limited the growth of Botrytis cinerea and Aspergillus flavus strains, produced cellulases and inulinases and enhanced cucumber seed germination in vitro. All examined surfactin overproducers produced siderophores and, additionally, KP7 and IM 14 solubilized phosphates. Among all examined surfactin overproducers only IM 13 during the growth in the presence of F. oxysporum mycelium (in dual liquid culture) increased about twofold surfactin and iturin secretion and almost completely suppressed fungal biomass growth. The obtained results revealed that the studied surfactin overproducers were equipped with various plant growth-promoting (PGP) traits allowing them to promote plant development in a diverse manner.

Evaluation of anthelmintic antimicrobial and antioxidant activity of Chenopodium album.

The objective of this study was to evaluate the anthelmintic, antimicrobial and antioxidant activities of Chenopodium album against gastrointestinal nematodes of sheep and some pathogenic microbes. A worm motility inhibition assay was used for in vitro study, and a faecal egg count reduction assay was used for an in vivo study. Various concentrations ranging from 100 to 500μg/ml of the extract were subjected to antimicrobial screening by disc diffusion method against four selected bacterial (Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas multocida and Escherichia coli) and two fungal (Aspergillus flavus and Candida albicans) strains in order to estimate the medicinal potential of the herb. DPPH (1,1-diphenyl-2-picrylhydrazyl), riboflavin photo-oxidation, deoxyribose, lipid peroxidation assays were used for antioxidant activity. The extracts exhibited dose- and time-dependent anthelmintic effects on the Haemonchus contortus as compared to levamisole. The extract showed maximum inhibitory effect against S. aureus (28±0.14mm), while as mild inhibitory effect was observed against E. coli among the selected microbial strains. The effect produced by the different extract concentrations was comparable with the standard antibacterial agent streptomycin sulphate and antifungal agent nystatin, which were used as effective positive control in the study. The antioxidant activity showed that the extracts exhibited scavenging effect in concentration-dependent manner on superoxide anion radicals and hydroxyl radicals leading to the conclusion that the plant has broad spectrum anthelmintic, antimicrobial and antioxidant activities and could be a potential alternative for treating various diseases.

Cloning and characterization of F3PYC gene encoding pyruvate carboxylase in Aspergillus flavus strain (F3)

Pyruvate carboxylase is a major enzyme for biosynthesis of organic acids like; citric acid, fumeric acid, and L-malic acid. These organic acids play very important role for biological remediation of heavy metals. In this study, gene walking method was used to clone and characterize pyruvate carboxylase gene (F3PYC) from heavy metal resistant indigenous fungal isolate Aspergillus flavus (F3). 3579bp of an open reading frame which encodes 1193 amino acid protein (isoelectric point: 6.10) with a calculated molecular weight of 131.2008kDa was characterized. Deduced protein showed 90-95% similarity to those deduced from PYC gene from different fungal strains including; Aspergillus parasiticus, Neosartorya fischeri, Aspergillus fumigatus, Aspergillus clavatus, and Aspergillus niger. Protein generated from the PYC gene was a homotetramer (α4) and having four potential N-linked glycosylation sites and had no signal peptide. Amongst most possible N-glycosylation sites were -N-S-S-I- at 36 amino acid, -N-G-T-V- at 237 amino acid, N-G-S-S- at 517 amino acid, and N-T-S-R- at 1111 amino acid, with several functions have been proposed for the carbohydrate moiety such as thermal stability, pH, and temperature optima for activity and stabilization of the three-dimensional structure. Hence, cloning of F3PYC gene from A. flavus has important biotechnological applications.

The growth and aflatoxin production of Aspergillus flavus strains on a cheese model system are influenced by physicochemical factors

Traditional cheeses may be contaminated by aflatoxin-producing Aspergillus flavus during the ripening process, which has not been sufficiently taken into account. The objectives of this study were to evaluate the influence of water activity (aw), pH, and temperature on the lag phases, growth, and aflatoxin production of 3 A. flavus strains (CQ7, CQ8, and CG103) on a cheese-based medium. The results showed that the behavior of A. flavus strains was influenced by pH, aw, and temperature conditions. The CQ7 strain showed the maximum growth at pH 5.5, 0.99 aw, and 25°C, whereas for CQ8 and CQ103 strains, no differences were obtained at pH 5.5 and 6.0. In general, low pH, aw, and temperature values increased the latency times and decreased the growth rate and colony diameter, although aw and temperature were the most limiting factors. Maximum aflatoxin production on the cheese-based medium occurred at pH 5.0, 0.95 aw, and 25 or 30°C, depending on the strain. This study shows the effect of pH, aw, and temperature factors on growth and aflatoxin production of 3 aflatoxigenic A. flavus strains on a cheese-based medium. The findings may help to design control strategies during the cheesemaking process and storage, to prevent and avoid aflatoxin contamination by aflatoxigenic molds.

Genotypic Regulation of Aflatoxin Accumulation but Not Aspergillus Fungal Growth upon Post-Harvest Infection of Peanut (Arachis hypogaea L.) Seeds.

Aflatoxin contamination is a major economic and food safety concern for the peanut industry that largely could be mitigated by genetic resistance. To screen peanut for aflatoxin resistance, ten genotypes were infected with a green fluorescent protein (GFP)—expressing Aspergillus flavus strain. Percentages of fungal infected area and fungal GFP signal intensity were documented by visual ratings every 8 h for 72 h after inoculation. Significant genotypic differences in fungal growth rates were documented by repeated measures and area under the disease progress curve (AUDPC) analyses. SICIA (Seed Infection Coverage and Intensity Analyzer), an image processing software, was developed to digitize fungal GFP signals. Data from SICIA image analysis confirmed visual rating results validating its utility for quantifying fungal growth. Among the tested peanut genotypes, NC 3033 and GT-C20 supported the lowest and highest fungal growth on the surface of peanut seeds, respectively. Although differential fungal growth was observed on the surface of peanut seeds, total fungal growth in the seeds was not significantly different across genotypes based on a fluorometric GFP assay. Significant differences in aflatoxin B levels were detected across peanut genotypes. ICG 1471 had the lowest aflatoxin level whereas Florida-07 had the highest. Two-year aflatoxin tests under simulated late-season drought also showed that ICG 1471 had reduced aflatoxin production under pre-harvest field conditions. These results suggest that all peanut genotypes support A. flavus fungal growth yet differentially influence aflatoxin production.

Assessment of heat-inactivated marine Aspergillus flavus as a novel biosorbent for removal of Cd(II), Hg(II), and Pb(II) from water.

A novel marine fungus was isolated and classified as Aspergillus flavus strain EGY11. The heat-inactivated form of isolated Aspergillus flavus was investigated and evaluated as a new eco-friendly and highly efficient biosorbent for removal of toxic heavy metals such as Cd(II), Hg(II), and Pb(II) from aqueous solutions. The SEM morphological studies of biosorbent-loaded metal ions confirmed their direct binding on the surface of heat-inactivated Aspergillus flavus. The metal biosorption capacity values were determined and optimized by the batch technique in the presence of various experimental controlling factors such as pH, contact time, biosorbent dosage, initial metal ion concentration, and coexisting species. The maximum metal capacity values of Cd(II), Hg(II), and Pb(II) were cauterized as 1550 (pH7.0), 950 (pH7.0), and 1000μmolg-1 (pH6.0), respectively. The equilibrium time for removal of metal ions was identified as 40min. The maximum sorption capacity values (1200.0-4000.0μmolg-1) were established by 5.0mg as the optimum mass of biosorbent. The collected biosorption data obtained from the equilibrium studies using the initial metal ion concentration were described by the Langmuir, Freundlich, Brunauer-Emmett-Teller (BET), and Dubinin-Radushkevich isotherm (D-R) isotherm models. The potential implementation of heat-inactivated Aspergillus flavus biosorbent for heavy metal removal from different water samples was successfully accomplished using multistage microcolumn technique. The results refer to excellent percentage recovery values in the ranges 92.7-99.0, 91.3-95.6, and 95.3-98.2% for the biosorptive removal of Cd(II), Hg(II), and Pb(II), respectively, from the examined environmental samples.

Biocontrol of toxigenic strain of Aspergillus flavus isolated from the root tubers of safed musli (Chlorophytum borivilianum Sant. F) using its rhizospheric mycoflora

Miraculous herb safed musli (Chlorophytum borivilianum Sant. F), family liliaceae, is well recognized for its immense potential as an aphrodisiac. The root tubers of this herbal drug were found to be invested with Aspergillus flavus during field and storage. Therefore, the present study was designed to explore the ability of 26 co-existing rhizospheric mycoflora to inhibit A. flavus invasion and subsequent aflatoxin contamination of safed musli. The interaction of these moulds with highly toxigenic strain (CB55) of A. flavus was evaluated by dual culture method and type of interaction was graded. Most likely antagonistic effects were shown by fifteen (15) moulds, out of which Type ‘C’ interaction was evidenced in the case of six moulds; A. clavatus, A. terreus, Botryotrichum piluliferum, Candida albicans, Cephalosporium acremonium, and Cunninghamella sp. Further, ‘D’ type interaction was displayed by seven moulds which include A. niger, Colletotrichum sp., Drechslera sp., Mucor haemalis, Mycelia sterilia, Rhizopus arrhizus and Stachybotrys atra and ‘E’ type interaction was noted in the case of Trichoderma viride and Trihcothecium roseum. Regarding human health it is critical to use an ecofriendly approach to control the invasion of toxigenic moulds with root tubers of safed musli.

Fullerol C60(OH)24 nanoparticles and mycotoxigenic fungi: a preliminary investigation into modulation of mycotoxin production.

Increased use of fullerols in various fields and expected increase of their environmental spread impose the necessity for testing fullerol nanoparticles (FNP) effects on microbiota. There is little information available on the interaction of mycotoxigenic fungi and FNP, despite FNP having a great potential of modifying mycotoxin production. Namely, FNP exhibit both ROS-quenching and ROS-producing properties, while oxidative stress stimulates mycotoxin synthesis in the fungi. In order to shed some light on the extent of interaction between FNP and mycotoxigenic fungi, the effects of fullerol C60(OH)24 nanoparticles (10, 100, 1000ng/mL) on mycelial growth, aflatoxin production and oxidative stress modulation in an aflatoxigenic strain of Aspergillus flavus (NRRL 3251) during 168h of incubation in a liquid culture medium were examined. FNP slightly reduced mycelial biomass weight, but significantly decreased aflatoxin concentration in media. Lipid peroxide content, superoxide dismutase, catalase and glutathione peroxidase activities suggest that FNP treatments hormetically reduced oxidative stress within fungal cells in turn suppressing aflatoxin production. These findings contribute to the assessment of environmental risk and application potential of fullerols.

The influence of ecophysiological factors on growth, aflR gene expression and aflatoxin B1 production by a type strain of Aspergillus flavus

Maize is prone to infection by Aspergillus flavus, which can contaminate the product with aflatoxins. The objective of this study was to examine the impact that interactions between water activity (aw) and temperature may have on growth, the expression of a biosynthetic regulatory gene (aflR) and aflatoxin B1 (AFB1) production by a strain of A. flavus on a maize-based medium. Results showed that there were some differences between lag phases and growth rates of A. flavus. The optimum growth rate for A. flavus was at 30 °C and 0.99 aw. No growth occurred at 0.90 aw and 20 °C. Both temperature and aw had an influence on the relative aflR gene expression and AFB1 production by A. flavus; however, the results for AFB1 production were not consistent with the effects on gene expression or growth. These findings provide data that are useful to better understand the conditions which represent higher risks from AFB1 production. However, the aflR expression was not a good indicator of AFB1 production alone. Thus, further molecular studies of other AF-related genes should be done. These results are discussed in the context of harvesting and storage of maize and the prevailing environmental conditions to minimise AFB1 contamination.

Abstract B23: Detection of susceptibility to childhood Acute Lymphoblastic Leukemia (ALL)

Abstract Currently, there are no known methods to predict of susceptibility to, and means for prevent Acute Lymphoblastic Leukemia (ALL). We have evaluated and patented a group of proteins dubbed Protein X from a certain strain of Aspergillus Flavus (AF) and developed methods for screening and identifying totally asymptomatic patients in remission of ALL, including long term survivors of this disease, distinguishing them from normal controls. Subject to institutional approved consents/assents, 15-20 ml of blood was obtained from 40 cases of ALL in children and young adults, including long term survivors of ALL. Controls were normal individuals, sickle cell patients undergoing partial exchange transfusion and patients with solid tumors. Mononuclear leukocytes (MNL) of ALL patients in remission and controls were separated using Ficoll Paque Plus (GE Healthcare). Epstein Barr virus (EBV) was obtained commercially. Positive and negative controls for Protein X were aflatoxin and Mycocladus Corymbifera (MC). Avian leukosis virus (ALV) was used as control for EBV. MNL were co-incubated with Protein X ± EBV ± irradiation, for periods of 1-72 hours. Controls were treated identically with appropriate substitutions. Test and control MNLs were examined for genetic markers, NF-κB and cell surface markers (CSM) including CD10/CD19, CD34/CD19, and CD34/CD117. Changes were expressed as percentage of control. Using ELISA, plasmas were tested for antibodies against Protein X ± EBV time experiments reveled 72 hours was optimum for achieving results. Upon 72 hours exposure of MNL from ALL to Protein X ± EBV, cells from ALL patents in remission developed cell surface phenotypes typical of ALL. This was not seen in controls. Addition of EBV ± radiation to Protein X, enhanced these effects in MNL of ALL and not controls. Changes were statistically significant and clearly separated ALL from controls. Evaluation of NF-κB revealed enhancement in ALL and not controls. Aflatoxin indiscriminately induced cell surface marker changes in both, normal and ALL, while ALV and supernatant of MC had no effect. ELISA, using Protein X ± EBV, distinguished ALL from controls. Gene array and biomarkers confirmed transformation to leukemic cell markers upon exposure to Protein X in cells from ALL patients but not controls. These studies reveal, in vitro, upon exposure to Protein X, unlike normal controls, MNL from ALL patients in remission develop cell surface phenotypes and genetic markers typical of ALL. These techniques have potential for screening for ALL and may have implications for etiology of ALL and its prevention. Citation Format: Cameron K. Tebbi. Detection of susceptibility to childhood Acute Lymphoblastic Leukemia (ALL). [abstract]. In: Proceedings of the AACR Special Conference: Improving Cancer Risk Prediction for Prevention and Early Detection; Nov 16-19, 2016; Orlando, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2017;26(5 Suppl):Abstract nr B23.

Biological Control of Aflatoxin Contamination in U.S. Crops and the Use of Bioplastic Formulations of Aspergillus flavus Biocontrol Strains To Optimize Application Strategies.

Aflatoxin contamination has a major economic impact on crop production in the southern United States. Reduction of aflatoxin contamination in harvested crops has been achieved by applying nonaflatoxigenic biocontrol Aspergillus flavus strains that can out-compete wild aflatoxigenic A.flavus, reducing their numbers at the site of application. Currently, the standard method for applying biocontrol A.flavus strains to soil is using a nutrient-supplying carrier (e.g., pearled barley for Afla-Guard). Granules of Bioplastic (partially acetylated corn starch) have been investigated as an alternative nutritive carrier for biocontrol agents. Bioplastic granules have also been used to prepare a sprayable biocontrol formulation that gives effective reduction of aflatoxin contamination in harvested corn kernels with application of much smaller amounts to leaves later in the growing season. The ultimate goal of biocontrol research is to produce biocontrol systems that can be applied to crops only when long-range weather forecasting indicates they will be needed.

English

This study examined the effect of water activity (0.85-0.995 aw) on growth rate and asexual spore production for four mycotoxigenic strains (Aspergillus flavus, Aspergillus ochraceus, Aspergillus carbonarius and Penicillium verrucosum) on Malt Extract Agar (MEA). The water activity levels of MEA media were modified ionically (NaCl) and non-ionically (glycerol). Results showed that the optimum aw for growth was at 0.98-0.995 for all species using both solutes. However, when water stress was inflicted, there was a slower growth for all species. The limit for growth of the strains was at 0.85-0.9 aw, there was no growth at 0.9 aw for A. carbonarius using NaCl solute and 0.85 aw for A. carbonarius and A. flavus using glycerol solute. A. ochraceus and P. verrucosum had a higher tolerance to lower water activity than A. carbonarius and A. flavus when modified with NaCl. There were significant differences in sporulation between species on glycerol and NaCl-amended media. The optimum conditions for production of asexual spores is often very different from that for growth. Little amount of conidial spore occurred at 0.93-0.95 aw modified with NaCl in cultures of A. carbonarius and P. verrucosum but high amounts were produced by A. ochraceus and A. flavus. Optimum water activity for spore production was 0.995 aw for A. carbonarius, 0.98 aw for P. verrucosum, 0.95 aw for A. flavus and 0.85 aw for A. ochraceus on modified media with glycerol. This is the first detailed study to examine the similarities and differences in growth and sporulation in response to the change of water activity level of important mycotoxigenic species. This study can help in understanding why these species are varied in mycotoxin production, so the results obtained in this study may be useful for application in systems of food safety management. Key words: Food fungi, osmotic, abiotic parameters, conidiospores

Integration of biological control and transgenic insect protection for mitigation of mycotoxins in corn

Biological control is known to be effective in reducing aflatoxin contamination of corn, and some transgenic corn hybrids incur reduced damage from corn earworm (Helicoverpa zea) than comparable non-Bt hybrids. We conducted seven field trials over two years to test the hypothesis that transgenic insect protection and biological control could be integrated to prevent mycotoxin contamination of corn. Corn hybrid N78N3111, expressing the highest degree of transgenic insect protection, was nearly 100 percent free from corn earworm damage and generally had less than half as much contamination from fumonisin compared to N78NGT, a near isogenic corn hybrid without insect protection. This insect protection, however, did not significantly prevent aflatoxin contamination. Soil application of non-aflatoxigenic biocontrol strains of Aspergillus flavus significantly reduced aflatoxin concentrations in corn. Biocontrol strain 21882 of A. flavus was especially effective and reduced aflatoxin contamination by about 90 percent over the seven field trials. There was no significant interaction between the insect protection and biocontrol treatments. Although no synergies were detected, the reduction of mycotoxins by both strategies supports application of both strategies in tandem. Economic factors external to the cost of the technologies will be a major determinant if the mycotoxin mitigation attained by use of these technologies will have a positive economic benefit.

English

The aim of this study is to explore the impact of Lycium halimifolium Mill leaves extracts on mycotoxin B1 production in vitro, as well as the inhibitor effect of the aflatoxin B1 synthesis by Aspergillus flavus strain. The strain was isolated, identified (gi |146746162 | EF409803.1.) and positively tested for the production of Aflatoxin B1. The antimycotoxinogenesis effect was investigated using L. halimifolium Mill leaves consisting of butanol and ethyl acetate fractions. Indeed, the fractions were tested to stop the secretion of aflatoxin B1 by A. flavus in submerged culture (YES), simultaneously. The growth of the strain was evaluated as biomass response. The antimycotoxinogenesis activity showed that the two fractions: ethyl acetate and butanol of L. halimifolium Mill leaves were able to inhibit significantly the synthesis of mycotoxin AFB1. Thus, the secretion inhibition percentage was calculated in comparison with the control, using HPLC-PDA technique, and estimated at 96.83% for butanolic fraction and 94.99% for ethyl acetate fraction. To verify its correlation with biomass, the growth inhibition percentage was also estimated. The results showed that the dry weight concentration under butanolic and ethyl acetate fractions was 1.6 and 2 g/l, respectively, corresponding to 65.22 and 56.53% of inhibition growth percentage. Key words: Aflatoxin B1, antimycotoxinogenesis activity, high performance liquid chromatography coupled with photodiode array detector (HPLC-PDA), natural extract.