Max Rubner Conference 2018: Fungi and Mycotoxins in Foods

The presentations covered issues such as global mycotoxin problems and governmental regulation, mycotoxin producing fungi and their detection, the occurrence and analytics of mycotoxins, the impact of mycotoxins on human health and the control of mycotoxin contamination. Because of the broad spectrum of the presentations, the participants were given a comprehensive overview about new scientific findings and developments in this field. The overall impression, after hearing all presentations, is that because of the extensive scientific input into mycotoxin research, a great step forward in understanding biological, molecular and chemical backgrounds of mycotoxin production has been achieved. However, the mycotoxin problem has not yet been completely solved. But rather on the contrary, even new problems like emerging or masked (modified) mycotoxins, as well as challenges due to climate change, seem to come up.

This situation is partially due to the high adaptability of the mycotoxin producing fungi to various environments. In this respect, it is well known that stress conditions, which may occur during growth on the field (drought, fungicides), during harvesting (drying) or during storage under controlled environmental conditions (reduced water activity, lower temperatures, changes in pH), which do not completely inhibit the fungus, may reduce the growth, but increase the production of mycotoxins. The production of mycotoxins, as secondary metabolites, is even discussed as a kind of adaptation to different environments. This kind of basic knowledge is important to develop targeted measures to control mycotoxin production. Moreover, knowledge about emerging and masked (modified) mycotoxins, which both may be toxic metabolites, is essential to correctly assess the safety of a given product. Some presentations have shown that climate change may be an important issue in the future. Current results already show that toxigenic fungal species, which usually occur in areas of higher temperatures, move towards other geographical areas, in which these species were formerly not found. As a result, mycotoxins produced by these species may now be found in products of geographical areas where they did not appear before. New prevention methods based on non-chemical, biological or technological principles, which were introduced in several presentations may be highly targeted, may have a high acceptance by the consumer and may be more sustainable than conventional ones.

In the session “Global Mycotoxin Problems and Regulation” experts on that topic reported
about current international EU financed projects, dealing with the prevention of mycotoxins based on new identified principles. The fact that several large international EU projects are being financed reflects the importance of the mycotoxin problem, recognized by authorities. One approach in these projects is the application of enzymes from higher fungi (Basidiomycetes) such as laccases or other hydrolyzing enzymes, which can be used to degrade contaminating mycotoxins. Natural food components, for example certain amino acids, also have inhibitory activities against the biosynthesis of different mycotoxins. However climate change may have a negative effect on control strategies, e. g. the resilience of control strategies may be reduced under changing climatic conditions. To ensure food safety in respect to the fact that mycotoxin biosynthesis still cannot be completely controlled, statutory limits are set for several mycotoxins in certain countries and for certain products. An overview about the current situation concerning these regulations was given.

In the session “Mycotoxin producing Fungi and their Detection” the biological background of the occurrence and molecular biology of ochratoxin producing Aspergillus carbonarius strains in grapes have been treated, as well as population analyses of trichothecene producing Fusarium species in cereals. The last analysis was performed in a high-throughput approach by using a Multiplex-Nano-PCR system with which more than 5000 reactions per run can be performed simultaneously. With this approach, the distribution of different Fusarium trichothecene chemotypes, from east to west Canada could be analysed. Clear geographical preferences of the particular chemotypes could be detected. Methods like LAMP (loop-mediated isothermal amplification), for the detection of specific mycotoxigenic fungi, and a MALDI-TOF-MS system for identification purposes have further been introduced. These systems speed up and support the identification of mycotoxigenic fungi, which otherwise can only be carried out by experts on taxonomy. A proper identification of mycotoxigenic fungi in foods is of real importance for the correct assessment of their safety.

In the session “Occurrence and Analytics of Mycotoxins”, the influence of climatic conditions on the occurrence of Fusarium mycotoxins in different wheat milling fractions was described. On wheat, completely different production kinetics between deoxynivalenol (DON) and zearalenone (ZON) was shown. Highest amounts of ZON were found in the bran compared to the flour fraction. Two presentations pointed to emerging and masked (modified) mycotoxins. Because of improved and sophisticated new multi-toxin methods with a profound increase in analytical performance, more emerging and masked mycotoxins are continuously being identified. Some of these can be produced in high amounts. However, the toxicological analysis and evaluation of these metabolites is still missing. Presentations about the uptake and biotransformation of Fusarium toxins, as well as the intestinal metabolism of modified forms of T2- and HT2-toxin in pigs gave insight into the fate (derivatization as well as degradation) of these toxins in the plant and animal metabolism. Concerning the mycotoxin problem in developing countries, which is especially prominent in certain African regions, two lectures were presented, one lecture about a partnership between European and African institutions dealing with food safety and another presentation about the mycotoxin menace in Sub-Saharan Africa. These lectures showed the world´s real mycotoxin problem. Mycotoxin concentrations (especially aflatoxin) in these regions are partly so high, that acute aflatoxicosis with fatal cases may occur as was reported in 2016 for Tanzania. Different approaches to combat this problem were presented, including a new collaborative project to prevent aflatoxin contamination between German and Kenyan partners.

In the session “Impact of Mycotoxins on Human Health”, topics such as the toxicity of mycotoxin mixtures as well as biomarker-based assessment of human exposure to citrinin were treated. In the first presentation, the importance of dose-response experiments of the single mycotoxins is stressed, before addressing questions about additive, synergistic or antagonistic activities of mycotoxin mixtures. Synergistic activities of mycotoxin mixtures are concentration-dependent. Furthermore, synergistically acting mycotoxin mixtures may reach a certain toxicity level at much lower concentrations than one mycotoxin alone. Because of its toxic influence at lower concentrations, the synergistic effect may pose a real risk for the consumer. Mycotoxin mixtures may easily occur after natural contamination of plant-type products. With biomarker analysis the human exposure to citrinin was analysed. This toxin could be identified in human blood serum as well as in urine. This biomonitoring revealed a frequent contact to citrinin by humans. Citrinin is currently not regulated, but these data may contribute to a more detailed assessment of its importance. A further presentation dealt with the carry-over of aflatoxin from animal feed to the cow´s milk. This again is especially problematic in African countries. However according to recent reports also feed from East European countries were contaminated by aflatoxin.

The last session treated the issue “Control of Mycotoxin Contamination”. Biological as well as technological measures may be used to keep mycotoxin contamination as low as possible, without using chemical fungicides. These approaches include biological control (application of non-aflatoxigenic A. flavus strains, mycoparasitic Trichoderma species or bacterial species of Bacillus spp. and Streptomyces spp. to suppress the growth of mycotoxin producing fungi), safety management systems (the food safety objective approach (FSO), an extension of the HACCP and other hygienic concepts), as well as technological control (adherence to certain technological hurdles like temperature, water activity, pH or methods like sorting, heating, alkaline treatment) along the food chain. The last approach was demonstrated along the milk, the grape and the cereal food chain. Finally, a presentation about control measures based on new principles finished the conference.

Taken together, the high standard presentations gave a comprehensive overview about the actual situation in combatting the mycotoxin problem as well as highlighting new emerging problems, like climate change or the appearance of new or masked mycotoxins for food safety and food security issues. For these reasons, mycotoxin research is and will continue to be an important research topic also at the Max Rubner-Institut.

contact for scientific information:
Prof. Rolf Geisen, Max Rubner-Institut

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