Interakcije nekih plijesni i aflatoksinogenog soja Asspergillus flavus NRRL 3251

The objective of this study was to evaluate biotic interaction between some mould species and active producer of aflatoxin B1 Aspergillus flavus NRRL 3251, co-cultured in yeast-extract sucrose (YES) broth. Twenty-five mould strains of Alternaria spp., Cladosporium spp., Mucor spp., A. flavus and A. niger, used as biocompetitive agents, were isolated from outdoor and indoor airborne fungi, scrapings of mouldy household walls, and from stored and post-harvest maize. Aflatoxin B1 was extracted from mould biomasses with chloroform and detected using the multitoxin TLC method. The results confirm antagonistic interaction between all strains tested. With Alternaria spp. and Cladosporium spp., aflatoxin B1 production decreased 100 %, compared to detection in a single culture of A. flavus NRRL 3251 (Cmean=18.7 µg mL-1). In mixed cultures with Mucor spp., aflatoxin B1 levels dropped to (5.6-9.3) µg mL-1, and the inhibition was from 50 % to 70 %. Four of five aflatoxin non-producing strains of A. flavus interfered with aflatoxin production in mixed culture, and reduced AFB1 productivity by 100 %. One strain showed a lower efficacy in inhibiting AFB1 production (80 %) with a detectable amount of AFB1 3.7 µg mL-1 when compared to control. A decrease in toxin production was also observed in dual cultivation with A. niger strains. It resulted in 100 % reduction in three strains), 90 % reduction in one strain (Cmean=1.9 µg mL-1) and 80 % reduction in one strain (Cmean=3.7 µg mL-1) inhibition.Cilj rada bio je procijeniti biotske interakcije između sojeva različitih vrsta plijesni i kontrolnog soja Aspergillus flavus NRRL 3251, producenta aflatoksina B1 (AFB1). Inhibitorno djelovanje u miješanim kulturama na tvorbu AFB1 ispitano je na dvadeset pet sojeva Alternaria, Cladosporium, Mucor i Aspergillus vrsta izoliranih iz zraka, strugotina pljesnivih zidova te uskladištenog i prezimljenog kukuruza. Biosinteze su provedene u tekućoj hranjivoj podlozi s kvaščevim ekstraktom (YESbujon). Ekstrakcije AFB1 iz biomase izvršene su multitoksinskom metodom tankoslojne kromatografije. Rezultati biotskih interakcija pokazali su antagonistički odnos svih testiranih sojeva. Alternaria i Cladosporium vrste simultano inokulirane sporama A. flavus NRRL 3251 inhibirale su tvorbu AFB1 100 % u odnosu na dokazani toksin u kontrolnoj biosintezi (konc. 18,7 µg mL-1). U miješanim kulturama vrstama roda Mucor dokazane su padajuće koncentracije AFB1 (9,3 µg mL-1, 7,5 µg mL-1 i 5,6 µg mL-1), odnosno inhibicija tvorbe toksina 50 % do 70 %. Atoksinogeni sojevi A. flavus inhibirali su tvorbu AFB1 80 % (1 soj, konc. 3,7 µg mL-1) i 100 % (4 soja). Antagonističko djelovanje prema toksinogenom soju, smanjujući tvorbu AFB1 u rasponu 80 % do 100 % (konc. 1,9 µg mL-1 i 3,7 µg mL-1), dokazano je u uzgojnim biosintezama s A. niger

Isolation of Bacteria with Antifungal Activity against the Phytopathogenic Fungi Stenocarpella maydis and Stenocarpella macrospora

Stenocarpella maydis and Stenocarpella macrospora are the causal agents of ear rot in corn, which is one of the most destructive diseases in this crop worldwide. These fungi are important mycotoxin producers that cause different pathologies in farmed animals and represent an important risk for humans. In this work, 160 strains were isolated from soil of corn crops of which 10 showed antifungal activity against these phytopathogens, which, were identified as: Bacillus subtilis, Pseudomonas spp., Pseudomonas fluorescens, and Pantoea agglomerans by sequencing of 16S rRNA gene and the phylogenetic analysis. From cultures of each strain, extracellular filtrates were obtained and assayed to determine antifungal activity. The best filtrates were obtained in the stationary phase of B. subtilis cultures that were stable to the temperature and extreme pH values; in addition they did not show a cytotoxicity effect against brine shrimp and inhibited germination of conidia. The bacteria described in this work have the potential to be used in the control of white ear rot disease

Chemical, Physical and Biological Approaches to Prevent Ochratoxin Induced Toxicoses in Humans and Animals

Ochratoxins are polyketide derived fungal secondary metabolites with nephrotoxic, immunosuppressive, teratogenic, and carcinogenic properties. Ochratoxin-producing fungi may contaminate agricultural products in the field (preharvest spoilage), during storage (postharvest spoilage), or during processing. Ochratoxin contamination of foods and feeds poses a serious health hazard to animals and humans. Several strategies have been investigated for lowering the ochratoxin content in agricultural products. These strategies can be classified into three main categories: prevention of ochratoxin contamination, decontamination or detoxification of foods contaminated with ochratoxins, and inhibition of the absorption of consumed ochratoxins in the gastrointestinal tract. This paper gives an overview of the strategies that are promising with regard to lowering the ochratoxin burden of animals and humans

Risks to human and animal health related to the presence of moniliformin in food and feed

The CONTAM Panel wishes to acknowledge all European competent authorities and other stakeholders that provided occurrence data on moniliformin in food and feed, and supported the consumption data collection for the Comprehensive European Food Consumption Database. Adopted: 21 November 2017Peer reviewedPublisher PD

Root-hair endophyte stacking in finger millet creates a physicochemical barrier to trap the fungal pathogen Fusarium graminearum

The ancient African crop, finger millet, has broad resistance to pathogens including the toxigenic fungus Fusarium graminearum. Here, we report the discovery of a novel plant defence mechanism resulting from an unusual symbiosis between finger millet and a root-inhabiting bacterial endophyte, M6 (Enterobacter sp.). Seed-coated M6 swarms towards root-invading Fusarium and is associated with the growth of root hairs, which then bend parallel to the root axis, subsequently forming biofilm-mediated microcolonies, resulting in a remarkable, multilayer root-hair endophyte stack (RHESt). The RHESt results in a physical barrier that prevents entry and/or traps F. graminearum, which is then killed. M6 thus creates its own specialized killing microhabitat. Tn5-mutagenesis shows that M6 killing requires c-di-GMP-dependent signalling, diverse fungicides and resistance to a Fusarium-derived antibiotic. Further molecular evidence suggests long-term host-endophyte-pathogen co-evolution. The end result of this remarkable symbiosis is reduced deoxynivalenol mycotoxin, potentially benefiting millions of subsistence farmers and livestock. Further results suggest that the anti-Fusarium activity of M6 may be transferable to maize and wheat. RHESt demonstrates the value of exploring ancient, orphan crop microbiomes

Mycological quality of foods in Burundi and antifungal metabolites of {\it Bacillus pumilus\/}

The microflora of various foods in Burundi was isolated and identified. Fusarium moniliforme was the predominant fungus isolated from corn and sorghum. Very few molds were isolated from rice and millet. Fusarium semitectum and Fusarium equiseti were the most common species isolated from haricot beans. Fusarium semitectum was also predominant in peanut samples. Peas were predominantly contaminated with Aspergillus ochraceus and Aspergillus wentii. Aspergillus flavus, Aspergillus niger and Aspergillus sydowi were the predominant species isolated from dried Ndagala fish. Penicillium citrinum, Penicillium corylophilum, and Penicillium chrysogenum were the predominant molds isolated from dried crushed cassava tuber and cassava flour.^ The ability of these molds to produce aflatoxins, cyclopiazonic acid (CPA) and fumonisins, as well as the presence of these mycotoxins in the foods were investigated. Thirty-seven of 95 isolates of Aspergillus flavus and all five isolates of Aspergillus parasiticus produced aflatoxins. Sixty-seven of the 95 isolates of Aspergillus flavus produced CPA. Ten of 20 isolates of Aspergillus oryzae and Aspergillus tamarii produced CPA. Fifty-one of 56 isolates of Fusarium moniliforme and all four isolates of Fusarium proliferatum produced fumonisins. Relatively high concentrations of fumonisin B\sb1 (12.2 to 75.2 $\mu$g/g) were detected in samples of corn and sorghum meal. Neither aflatoxins nor CPA were found in any of the foods.^ Bacillus pumilus produced an extracellular metabolite inhibiting mycelial growth and/or mycotoxin production of many Aspergillus, Fusarium and Penicillium species. The metabolite was isolated by precipitation with ammonium sulfate. It was soluble in water and other relatively polar solvents. The metabolite was heat stable (121\sp\circC for 30 minutes) and active over a wide range of pH (2 to 10). It was resistant to hydrolysis by proteases, peptidases and other enzymes. The metabolite was also resistant to denaturation by protein-denaturing detergents. Based on its resistance to hydrolysis by carboxypeptidase A and negative reaction with fluorescamine and ninhydrin, the metabolite appeared to be either a protein/peptide with blocked carboxyl and amine termini or a non-protein/peptide.

Reduction of Moniliformin During Alkaline Cooking of Corn

The incidence of moniliformin (MON) producing Fusarium spp. in selected corn (Zea mays L.) samples from Mexico and the United States and the effects of alkaline cooking and the tortilla manufacturing processes on the reduction of MON were determined. The percentage of infected kernels with Fusariumspp. ranged from 0 to 22% in eight food-grade corn samples, including six from Mexico and two from the United States. Complete (100%) reduction of MON was observed when a naturally contaminated com sample containing 1.4 µg of MON/g of corn was used in a pilot-scale alkaline cooking and tortilla manufacturing process. In a companion laboratory-scale study, using a cultured corn sample containing 17.6 µg of MON/g of corn, a 71 % reduction of the toxin was observed during the process. Alkaline cooking appeared to be an effective method for reduction of MON in corn