S1.26 <strong>Journal</strong> <strong>of</strong> <strong>Plant</strong> <strong>Pathology</strong> (2011), 93 (1, Supplement), S1.19-S1.26 EXTRACELLULAR DEGRADATION OF AFLATOXIN BY CERTAIN FUNGI PREVIOUSLY IDENTIFIED AS AFLA- TOXIN B1 BIODESTRUCTORS. N. Zhemchuzhina 1 , L. Shcherbakova 1 , O. Mikityuk 1 , T. Nazarova 1 , B. Campbell 2 . 1 Russian Research Institute <strong>of</strong> Phytopathology, RAAS, B. Vyazemy, Moscow 143050, Russia. 2 USDA, ARS, WRRC, <strong>Plant</strong> Mycotoxin Research, Albany, CA, USA. E-mail: zemch@mail.ru Several species <strong>of</strong> the genus Aspergillus are common opportunistic fungal pathogens <strong>of</strong> plants. They <strong>of</strong>ten infect many economically important crops in the field, and can also develop on agricultural feedstock and food products during post-harvest. These fungi also produce mycotoxins, most notably aflatoxins, which possess hepatotoxic, carcinogenic, teratogenic and mutagenic properties. Aspergillus flavus is one <strong>of</strong> the main aflatoxin producers. Pre- and post-harvest infection by A. flavus can result in contamination <strong>of</strong> food products with aflatoxin B1 (AFB1). Like other aflatoxins, there is currently no feasible method to decontaminate AFB1. Thus, AFB1 contamination is a serious food safety issue, in addition to being an economic problem, on a global scale. The only current remedy is to physically remove contaminated products from the processing stream. However, this is expensive and can result in an extensive loss <strong>of</strong> product. Chemical methods for detoxification, such as ammoniation under high pressure and temperature, have obvious drawbacks. Therefore, development <strong>of</strong> an environmentally appropriate and safe method for decontamination <strong>of</strong> agricultural material contaminated with aflatoxin would be a major advancement for food safety and quality. One promising approach for decontamination is enzymatic catabolism <strong>of</strong> aflatoxin by microbial “biodestructors” which occupy ecological niches conjointly with toxigenic A. flavus strains. We previously showed that 28 out <strong>of</strong> 41 fungal micromycetes screened that co-colonize natural substrates with aflatoxigenic A. flavus, were able to degrade AFB1. The most active biodestructors catabolized 80-98% <strong>of</strong> AFB1 added to media. Our current study shows that some <strong>of</strong> these biodestructors produce aflatoxin-degrading enzymes extracellularly. Strains <strong>of</strong> Phoma glomerata, Ph. exigua, Ph. chryzanthemicola, Trichoderma sp., T. viride, Cladosporium sp., Chaetomium sp., Ulocladium sp., Colletotrichum atramentarium, C. coccoides, Ophiobolus sp., Gliocladium roseum and Verticillium tenerum were grown on liquid Czapek with casein hydrolyzate at 28°C, at 200 rpm for 7 days. Mycelia were removed from cultural liquid by filtration through filter paper. This filtrate was sterilized by further filtration through a sterile 0.22 µm Millipore membrane. The resulting filtrate <strong>of</strong> culture liquid (FCL) was used for further studies. AFB1 between 5 to 10 m/kg, dissolved in 95% ethanol, was added in 1 ml samples to FCLs. These samples were incubated at 28°C for 3 days under aseptic conditions. Amounts <strong>of</strong> AFB1 remaining in the FCLs were quantified by HPLC and compared to that <strong>of</strong> controls (water and aflatoxin). Results indicated the Phoma fungi were the most promising sources <strong>of</strong> AFB1-degrading enzymes. FCLs <strong>of</strong> Ph. chryzanthemicola, Ph. glomerata and Ph. exigua removed about 32, 66 and 99% <strong>of</strong> the added toxin, respectively. FCLs <strong>of</strong> some other biodestructors, such as Gliocladium roseum, Colletotrichum atramentarium and Ulocladium sp., also contained extracellular catabolizing activity against AFB1. AFB1 content in the FCLs <strong>of</strong> these fungi showed a decline <strong>of</strong> 43.5 or 62% in AFB1, as compared to controls. Interestingly, although the Cladosporium sp. and Chaetomium sp. showed impressive toxin degrading ability under culture, their respective FCLs were inactive.
IMPACT OF PLANT PATHOGENS ON FOOD QUALITY OF AGRICULTURAL CROPS AND WINE DAY 2
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