1,721,075 research outputs found
A proteomic investigation of Aspergillus carbonarius exposed to yeast volatilome or to its major component 2-phenylethanol reveals major shifts in fungal metabolism
Full text linkSelection of Bacillus spp. with decontamination potential on multiple Fusarium mycotoxins
No full textAlong with Aspergillus and Penicillium spp., mycotoxins produced by Fusarium species are important contaminants in food and feed industry. This study was designed to investigate the biodegradation potential of a collection of Bacillus spp. in different substrates artificially contaminated with single or multiple Fusarium mycotoxins. B. megaterium BM344-1 and B. pumilus BP344-3 showed the highest degradation (100%) of zearalenone (ZEN) on liquid Luria Bertani (LB) medium. Bacillus cereus BC344-2, Bacillus cereus BC399-2, Bacillus simplex BS350-3 and Paenibacillus favisporus PF341, showed significant biodegrading capacity on T-2 toxin, leading to 72, 70, 71 and 88% decontamination, respectively. Complete degradation (100%) of ZEN was observed at a contamination level of 0.375 μg/ml in LB, while showing a decreasing trend of degradation (87 and 84%) at increasing levels of mycotoxins (0.750 and 1.50 μg/ml LB medium, respectively). Likewise, BM344-1 showed a decreasing degradation trend (81, 78% and 55%) at increasing T-2 contamination levels (0.3, 0.6 and 1.2 μg/ml, respectively). The ability of BM344-1 to degrade fumonisin B1 (FB1) and fumonisin B2 (FB2) was 14 and 12%, respectively. In LB medium concurrently contaminated with multiple mycotoxins (ZEN+T-2+HT-2+FB1+FB2), the degradation ability of BM344-1 was not affected by low-to-medium levels of each mycotoxin, while it was significantly lowered upon addition of each toxin at higher levels. In vivo mycotoxin degradation potential of BM344-1 tested on artificially contaminated maize showed 25-44% reduction of ZEN and 15-19% reduction of T-2, with a non-significant effect in case of combined mycotoxins contamination. B. megaterium BM344-1, having significant biodegrading properties on multiple Fusarium mycotoxins, can be considered for its potential application as a mycotoxin decontamination agent in the food industry
Development Of Bio-Insecticides Based On Local Qatari Bacillus Thuringiensis Strains For The Biological Control Of Harmful Dipteran Disease Vectors
Full text linkThe very friendly bacterium Bacillus thuringiensis (Bt) is the main source of environment-friendly and safe bioinsecticides used in the control of plant pests and animal and human disease vectors. A collection of 441 Qatari Bt strains were characterized and classified based on crystal morphology, plasmid patterns, crystal protein patterns and cry and cyt genes. In summary, the Bti strain QBT220 was recognized as the most efficient against Dipteran insects Aedes Aegypti. Two of its clones obtained by plasmid curing showed an increase of 115% in the -endotoxins. As example of novel Bt strains, QBT674 is a spherical crystal producing strain having cry2 gene but no cuboidal crystals. QBT555 is a Non-Bti strain with molecular profile very different from Bti strains, but expresses proteins like Cry11, Cry10 and Cyt1A. QBT229 showed high cytolytic activity due to five amino acid replacements in its β sheet that enhanced its anti-cancer activity
Hydrocarbon Degrading Candidate Bacteria Isolated From Qatar Polluted Soil and Molecular Identification of Key Enzymes Coding Genes
Full text linkSixteen bacterial strains were isolated form contaminated soils and identified as Bacillus subtilis, Bacillus circulans, Burkholderia cepacia, Pseudomonas aeruginosa, Micrococcus luteus, Raoultella ornithinolytica and Staphylococcus capitis. The hydrocarbon degradation potentialities of these strains revealed that they can be considered as good degraders of diesel, toluene and xylene reaching high biomasses indiesel as sole carbon source and high efficiencies of degradation of different molecular weight hydrocarbons. These hydrocarbon catabolism potentialities were confirmed by the identification and sequencing of seven key genes encoding haloalkane dehalogenase, hydrocarbon binding protein, alkane 1-monooxygenase, alkane hydroxylase, naphthalene dihydrodiol dehydrogenase, 1,2-Dihydroxynaphthalene dioxygenase, toluene monooxygenase large ? subunit and xylanase. These findingsdemonstrate the importance of both the strains and gene bank since having very highvalues and can be exploited for many applications including the enhancement of the genes expression in order to create improved hydrocarbon degrading strains to becomeone of the best environmentally friendly solution in bioremediation, competing with chemical and physical methods and allowing to achieve highest remediation efficiencies
Isolation of a Novel Kluyveromyces marxianus Strain QKM-4 and Evidence of Its Volatilome Production and Binding Potentialities in the Biocontrol of Toxigenic Fungi and Their Mycotoxins
Full text linkTo overcome the economic losses associated with fungi and their toxic metabolites, environmentally safe and efficient approaches are needed. To this end, biological control using yeasts and safe bacterial strains and their products are being explored to replace synthetic fungicides. In the present study, the biocontrol effect of a yeast strain of Kluyveromyces marxianus, QKM-4, against the growth and mycotoxin synthesis potential of key toxigenic fungi was evaluated. In vitro assays were performed to find the application of yeast volatile organic compounds (VOCs) against fungal contamination on important agricultural commodities. The removal of ochratoxin A (OTA) and deoxynivalenol (DON) by living and heat-inactivated yeast cells was also explored. VOCs produced by strain QKM-4 were able to significantly limit the fungal growth of 17 fungal species belonging to genera Aspergillus, Penicillium, and Fusarium. Yeast VOCs were able to reduce OTA biosynthesis potential of Penicillium verrucosum and Aspergillus carbonarius by 99.6 and 98.7%, respectively. In vivo application of QKM-4 VOCs against Fusarium oxysporum and A. carbonarius infection on tomatoes and grapes, respectively, determined a complete inhibition of fungal spore germination. GC/MS-based analysis of yeast VOCs identified long-chain alkanes, including nonadecane, eicosane, docosane, heptacosane, hexatriacontane, and tetracosane. In vitro testing of the mycotoxin-binding potential of the living and heat-inactivated QKM-4 cells showed a reduction of OTA and DON up to 58 and 49%, respectively, from artificially contaminated buffers. Our findings clearly demonstrate the strong antifungal potential of K. marxianus QKM-4 and propose this strain as a strong candidate for application in agriculture to safeguard food and feed products
Perfume Guns: Potential of Yeast Volatile Organic Compounds in the Biological Control of Mycotoxin-Producing Fungi
Full text linkPathogenic fungi in the genera Alternaria, Aspergillus, Botrytis, Fusarium, Geotrichum, Gloeosporium, Monilinia, Mucor, Penicillium, and Rhizopus are the most common cause of pre- and postharvest diseases of fruit, vegetable, root and grain commodities. Some species are also able to produce mycotoxins, secondary metabolites having toxic effects on human and non-human animals upon ingestion of contaminated food and feed. Synthetic fungicides still represent the most common tool to control these pathogens. However, long-term application of fungicides has led to unacceptable pollution and may favour the selection of fungicide-resistant mutants. Microbial biocontrol agents may reduce the incidence of toxigenic fungi through a wide array of mechanisms, including competition for the ecological niche, antibiosis, mycoparasitism, and the induction of resistance in the host plant tissues. In recent years, the emission of volatile organic compounds (VOCs) has been proposed as a key mechanism of biocontrol. Their bioactivity and the absence of residues make the use of microbial VOCs a sustainable and effective alternative to synthetic fungicides in the management of postharvest pathogens, particularly in airtight environments. In this review, we will focus on the possibility of applying yeast VOCs in the biocontrol of mycotoxigenic fungi affecting stored food and feed
Biological Control Of Mycotoxigenic Fungi And Associated Mycotoxins By The Application Of Bacterial And Yeast Antifungal Compounds
Full text linkMycotoxins are secondary metabolites of mycotoxigenic fungi and are
considered as a serious threaten to the life of humans and animals, since some of these
mycotoxins are carcinogenic compounds.
In this M.Sc research project, we demonstrated that the low fermenting yeast L.
thermotolerans 751 has a great antifungal potential through the synthesis of Volatile
Organic Compounds (VOC) that are able to act against the mycotoxigenic fungi and
the synthesis of their mycotoxins. L. thermotolerans 751 has also shown a great
adsorption potential to mycotoxins in in-vitro experiments. In addition, these VOCs
were applied in in-vitro experiments to inhibit the fungal growth and spores’
germination and protection of fungi inoculated tomato fruit, for more than one month.
On the other hand, our second biocontrol agent, the Qatari bacterial strain Burkholderia
cepacia (QBC03) has shown a broad antifungal spectrum and a very efficient inhibition
of the synthesis of mycotoxins.This research work was made possible by the sponsorship of Qatar National
Research Foundation; NPRP grant #8-392-4-00
Investigation and Biological Control of Toxigenic Fungi and Mycotoxins in Dairy Cattle Feed
Full text linkMycotoxins are secondary metabolites synthesized by mycotoxigenic fungi,
contaminating human and animal food and feed. Aflatoxin B1 (AFB1) and ochratoxins
(OTA) are frequently detected in animal feed products causing many health issues in
humans and animals.
In this M. Sc research work, we evidenced the presence of OTA and AFs below the EU
maximum permissible limits. Mycotoxigenic fungal strains have been isolated from the
animal feeds. The morphological and molecular identification of these toxigenic fungi
allowed the evidence of A. flavus, A. niger, A. carbonarius and P. verrucosum that
synthesize during their growth mycotoxins compounds (Aflatoxins & Ochratoxins) at
levels higher than the detection limits and the corresponding genes were evidenced.
In order to set up safe and efficient biological control strategy of these mycotoxigenic
fungi, we decided to use yeasts known to be very safe for such purpose. Thus, in the
second part of this Thesis, 14 yeast strains were isolated from different fermented food,
dairy and meat products. These strains showed a great antifungal and spectrum of
activities through the synthesis of Volatile Organic Compounds (VOCs). Among these
yeast strains, a particular strain of Kluyveromyces marxianus QKM-4, had the strongest
antifungal VOCs that we were able to identify. GC/MS based analysis of yeast VOCs showed long chain alkanes including nonadecane (C19), eicosane (C20), docosane
(C22), heptacosane (C27), hexatriacontane (C36) and tetracosane (C24) that can control
the mycotoxigenic fungal strains and their mycotoxins synthesis. Testing the mycotoxin
binding potential of the live and heat-inactivated QKM-4 cells, showed the reduction
of OTA and DON up to 58% and 49%. The findings of the present study clearly
demonstrate a strong antifungal potential of Kluyveromyces marxianus QKM-4 for its
possible application in the agriculture and food industry. In another applied part of the
present work, the strain QKM-4 of Kluyveromyces marxianus showed a great inhibition
potential of the mycotoxigenic fungal growth, spore’s germination and 100% protection
of tomato and grape fruits from the in vitro infection of the latter by mycotoxigenic
fungi for more than 10 days
INVESTIGATION AND PRODUCTION OF BIOINSECTICIDES BASED ON NEWLY BACILLUS THURINGIENSIS STRAINS ISOLATED FROM QATAR FOR THE DEVELOPMENT OF A BIOLOGICAL AGRICULTURE AND SAFE FOOD PRODUCTION IN QATAR
No full textBacillus thuringiensis produces parasporal crystals responsible of their insecticidal activity against specific insect orders. Eight newly isolated Bt strains produce different parasporal crystal and have several genetic profiles. Three local Bt strains were very active against the disease vector insect Culex. Pipiens. The strain QBT755 showed high stability under at 42°C compared to other strains. All the explored strains showed important ?-endotoxin production capacity. The formulation of final bioinsecticides was very successful. In addition, QBT755 produces Cyt1a cytolytic protein responsible of anti-cancer activity (data unpublished). Its gene cyt1A was successfully expressed downstream a strong E. coli promoter. The recombinant strain of E. coli has shown its growth kinetics affected by the expressed Cyt1A protein, demonstrating new avenues for the industrial production of Cyt1A for biocontrol, as well as cytolytic applications in pharmaceutical industries. All these strains can be considered as potential native candidates for the production of efficient biopesticides
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