Aspergillus species as mycotoxin producers in agricultural products in central Europe

Abstract

Aspergillus species are able to produce a range of mycotoxins, includ?ing e.g. aflatoxins, ochratoxins, fumonisins and patulin. Aflatoxins are mainly produced by members of Aspergillus section Flavi, and they contaminate various agricultural products in several parts of the world. Several recent reports have indicated that aflatoxin-producing fungi and consequently aflatoxin contamination occur in agricultural commodities in a number of European countries which have not been faced with this problem before. Indeed, recent surveys have clarified that concentrations of aflatoxins in maize products and milk has been exceeding the EU limit in several regions of Central Europe including Serbia, Slovenia, Croatia, Northern Italy and Romania. However, aflatoxin contamination and aflatoxin-producing Aspergillus species have not been identified yet in maize in Hungary. We examined the presence of potential aflatoxin-producing Aspergilli in maize samples collected in southern parts of Hungary. Several A. flavus isolates were identified, and pre?liminary results indicated that some of the isolates were able to produce aflatoxins. Con?tamination of other agricultural products with aflatoxins can also pose problems in Central Europe due to global warming. Ochratoxin contamination of grapes and grape-derived products is usually caused by black Aspergilli, especially by A. carbonarius and A. niger, although these species have been rare in Central European vineyards due to climatic fac?tors. Ochratoxin contamination of other agricultural products including spices and cereals was also observed in the region. Besides, ochratoxin producing Aspergilli are frequently isolated from imported products including coffee beans, dried fruits and spices, and ochra?toxin contamination of these samples was also observed. Fumonisins are produced mainly by Fusarium species, and by the recently identified producers Aspergillus niger and A. awamori. We examined fumonisin producing abilities of A. niger / A. awamori isolates col?lected from the variety of substrates including raisins, figs, dates, maize and onions. The isolates, which came from dried vine fruits, produced several fumonisin isomers also pre?sent in the raisin samples, indicating that fumonisin contamination of these products was probably caused by black Aspergilli. Besides, strains collected from figs, dates and onions were also able to produce fumonisins, and preliminary data indicated that figs and onions were also contaminated with low but significant amount of fumonisins. Potential fumonisin producing A. awamori isolates were also identified on maize samples. Further studies on the examination of the occurrence of fumonisins and their potential producers in other agricultural products are in progress. Regarding patulin, contamination of apple based products is a serious problem in the region, mainly caused by Penicillium species. Although patulin producing Aspergilli have also been identified in cereals, patulin contamination of cereals and cereal based products is usually low in Central Europe.Aspergillus vrste su sposobne da proizvedu velik broj mikotoksina, ukljucujuci aflatoksine, ohratoksine, fumonizine i patulin. Aflatoksine pretezno proizvode pripadnici vrste Aspergillus, sekcije Flavi, i kontaminiraju razlicite poljoprivredne proizvode u nekoliko svetskih regija. Nekoliko poslednjih istrazivanja ukazuju da kontaminacije poljoprivrednih proizvoda plesnima, producentima aflatoksina a samim tim i aflatoksinima pocinju da se pojavljuju i u zemljama Evropske unije koje se ranije nisu suocavale sa ovim problemom. Prema nedavno objavljenim podacima, potvrdjeno je prisustvo aflatoksina u kukuruzu i mleku u kolicinama koje prelaze maksimalno dozvoljene granice prema EU regulativi, u nekoliko regiona centralne Evrope ukljucujuci Srbiju, Sloveniju, Hrvatsku, severnu Italiju i Rumuniju. Medjutim, kontaminacija kukuruza aflatoksinima i toksigenim plesnima jos nije primecena u Madjarskoj. Mi smo ispitivali prisustvo plesni, potencijalnih producenata toksina iz roda Aspergillus, u uzorcima kukuruza prikupljenih u juznim oblastima Madjarske. Identifikovano je prisustvo nekoliko izolata A. flavus i preliminarni podaci ukazuju na njihovu sposobnost da produkuju aflatoksine. Ocekuje se da ce kontaminacija aflatoksinima i drugih poljoprivrednih proizvoda osim kukuruza postajati sve ozbiljniji problem za centralnoevropske zemlje kao posledica globalnog otopljavanja. Kontaminaciju grozdja i srodnih proizvoda ohratoksinom izazivaju crni Aspergilli, narocito A. carbonarius i A. niger, iako se ove vrste retko srecu u vinogradima centralne Evrope usled klimatskih faktora. U ovom regionu je takodje zapazena pojava kontaminacije ohratoksinima i drugih proizvoda kao sto su zita i zacini. Takodje, plesni ovog roda, producenti ohratoksina, cesto mogu da se izoluju iz uvoznih proizvoda kao sto su zrna kafe, suseno voce i zacini a registrovana je i kontaminacija ovih proizvoda ohratoksinom. Fumonizine proizvode vrste roda Fusarium kao i nedavno identifikovani Aspergillus niger i A. awamori. U nasim istrazivanjima smo ispitivali sposobnost produkcije fumonizina od strane A. niger/A. awamori u razlicitim supstratima, ukljucujuci suvo grozdje, smokve, urme, kukuruz i crni luk. Izolati iz suvog grozdja su bili sposobni da produkuju nekoliko izomera fumonizina koji su bili prisutni u uzorcima suvog grozdja, ukazujuci da je konatminacija suvog grozdja fumonizima najverovatnije uzrokovana crnim Aspergillus vrstama. Pored toga, sojevi izolovani iz smokve, urme i crnog luka su takodje pokazali sposobnost proizvodnje fumonizina a preliminarni podaci pokazuju da su smokva i crni luk bili kontaminirani niskim ali znacajnim kolicinama fumonizina. Izolati potencijalnog producenta fumonizina A. awamori su takodje izolovani u uzorcima kukuruza. U toku su istrazivanja o prisustvu fumonizina i njihovih potencijalnih producenata i u drugim poljoprivrednim proizvodima. Sto se tice patulina, kontaminacija proizvoda od jabuka je veoma ozbiljan problem u ovoj regiji a uglavnom ga izazivaju vrste roda Penicillium. Iako je u zitu identifikovano prisustvo producenata patulina iz roda Aspergillus, kontaminacija zita i proizvoda od zita patulinom je uglavnom neznatna u centralnoj Evropi.