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AUTHOR COMMENTARIES - From Special Topics

Mycotoxins - May 2008

Krska Professor Rudolf Krska
From the Special Topic of Mycotoxins

Mycotoxins are natural metabolites produced by fungi infecting cereals, either as crops in the field or found in grain in storage. More than 300 mycotoxins have already been chemically characterized, but the total number of secondary fungal metabolites is estimated to be more than 20,000. National and international bodies such as the US Food and Drug Administration, the European Commission, and the World Health Organization have recognized the health risks to animals and humans caused by mycotoxins entering the food chain.


These institutions have compiled comprehensive directives to regulate the permitted levels of mycotoxins in food and animal feed. Appropriate drafting of regulations for trace contaminants is critically dependent on tools from analytical chemistry because the screening of food and feed needs to be fast, cost-effective, and accurate.

A Special Topics examination of mycotoxins research over the past decade ranks the research of Professor Rudolf Krska at #2 by total number of papers, and at #4 by total citations. His record in this analysis includes 48 papers cited a total of 546 times. Three of these papers have been named as Highly Cited Papers in Essential Science IndicatorsSM from Thomson Reuters.

Professor Krska is head of the Center for Analytical Chemistry at the University of Natural Resources and Applied Life Sciences, Vienna, Austria. In the interview below, Dr. Simon Mitton, ScienceWatch.com's European correspondent, talks with Professor Krska to find out more about his high-ranking papers published in the past 10 years.

  Globalization means that the food industry has to take biosecurity extremely seriously, so that's why UN agencies such as WHO have a hand in making regulations for toxins in our food. The Special Topics analysis by Clarivate Analytics shows that you have been making state-of-the-art contributions to the development of tools that can detect mycotoxins in cereal-based food. How did you become an analytical chemist specializing in these contaminants?

I graduated from the High School here in Vienna. From there I attended the Vienna University of Technology, where I received my diploma in chemistry. That's where my interest in agricultural and environmental pollutants started, because my thesis topic was on the decontamination of soils polluted by cyanides.

The next step for me was a Ph.D., and for that the thesis concerned the development of a new infrared fiber-optic sensor for chlorinated hydrocarbons in water.

  So your interest in toxicology moved in the direction of improving the analytical techniques for the detection of contaminants?

Very much so. My interest in mycotoxins in particular started when I was a postdoc working in Ottawa with Health Canada. My mentor there was Peter M. Scott, a world expert in the field, and we have remained firm colleagues ever since I returned to Vienna.

  Why should we be concerned about mycotoxins?

They are potent toxins with a wide range of actions on humans and animals. An extensive literature describes neurotoxic, carcinogenic, mutagenic, immunosuppressive, and estrogenic effects of mycotoxins. Although the greatest risk to humans comes from the direct contamination of food, the entry of mycotoxins into the food chain via eggs, milk, and meat should not be overlooked. However, health issues as a result of mycotoxin contamination of human food are restricted to developing countries. Nonetheless, in industrial countries mycotoxin contamination is an important agricultural problem and thus related to feed stuffs. Mycotoxins are persistent: they are usually not broken down in digestion, nor does cooking destroy them.

There are hundreds of them, and from the point of view of organic chemistry they exhibit great structural diversity that leads to different chemical properties, and that variety is of course a challenge in terms of detection techniques.

Aflatoxins, which are produced by the Aspergillus species, can be deadly. In 2004 more than 100 people died in Kenya after eating home-grown maize that was contaminated.

The toxins in which I specialize are produced by several species of the genus Fusarium. They include trichothecene mycotoxins such as deoxynivalenol and zearalenone. They are also very stable and can survive cooking. The trichothecenes are not acutely toxic but they can weaken the immune system and can cause vomiting and diarrhea.

  What are the main research areas at your Center of Analytical Chemistry?

The Center comprises about 35 professionals in chemistry. We cover three major areas.

One is mycotoxin research in general, not just the chemical analytical techniques for detecting these substances in different commodities. We also study microbial reaction processes of these mycotoxins by microbes, as a means to degrade the toxins in vivo. Our research has continuously shifted towards metabolomics, an area where we study the interactions between plants and fungi, and the resulting range of bioactive metabolites. Metabolic profiling is also an important tool in toxicology. We have now shifted the emphasis from target analysis to understanding the whole range of possible metabolites that are formed in plants.

Our second area is water analysis, where we are organizing proficiency testing schemes.

Our third area is the development of rapid test methods. This covers immunochemical assays, and lateral flow devices, both for rapid on-site detection of mycotoxins as well as for allergenic proteins in food.

  Your papers show that you've made important progress in speeding up analysis, particularly by increasing the number of identifications that can be made via a single process.

You bet! In 2006 my group scooped a $50,000 prize for the development of a fast and reliable method of mycotoxin detection. We won that award for the development of fully C13-labeled mycotoxins and the quick detection of 12 different mycotoxins, but we have since developed our technique so that it can handle as many as 87 toxins at a time. Our analysis has shifted from single identifications to broad spectrum analysis.

We have been among the first to develop multitoxin methods by mass spectrometry, particularly for masked mycotoxins, and that's the topic of the 2005 Journal of Agriculture and Food Chemistry paper, "Masked mycotoxins: Determination of a deoxynivalenol glucoside in artificially and naturally contaminated wheat by liquid chromatography-tandem mass spectrometry," (Berthiller F, et al., 53:3421-5). These masked mycotoxins were first detected by us. They escape routine analysis but can cause intoxication once the free toxin is released again during digestion. Our breakthrough increased the awareness of toxins that are not apparently there but are still a potential threat to human and animal health.

  Several of your highly cited papers are on trichothecenes. I note that these are papers on applications, with the emphasis on detection.

The toxicological potential of the many mycotoxins can obviously be quite different depending on the fungal species from which they have been produced. The most toxic are the aflatoxins, and that has been known since the 1960s. However, my specialty has always been a focus on the Fusarium mycotoxins which are most prevalent in the moderate climatic regions of the world.

These Fusarium mycotoxins do show much less toxicity compared to aflatoxins. The most prevalent mycotoxins, and the subject of my most-cited papers, are the trichothecenes, which do not show acute toxicity. However, they can occur at quite high levels sufficient to cause vomiting and weakening the immune system—that's a major issue here. But I must point out that these mycotoxins are also more important for animal feed rather than for food. It is mainly an agricultural problem in the first instance and only secondarily about food.

  Are the regulatory authorities the main drivers of the impact of your practical papers on analysis?

Yes, that's particularly the case for the most prevalent Fusarium mycotoxins. There is new legislation which came into force in 2006, and that certainly has increased the awareness of these toxins. For example, the European regulation on deoxynivalenol in bread includes a maximum accepted level of 500 ng g-1, 500 parts per billion. Also in the couple of years before 2006, people were already aware that new regulations were coming into play, and that's one of the reasons why interest in the analysis of these compounds increased.

My most-cited paper from this analysis, "The state-of-the-art in the analysis of type-A and -B trichothecene mycotoxins in cereals," (Krska R, et al., Fresen. J. Anal. Chem. 371: 285-99, 2001), probably drew attention due to the expected EU-regulations. In addition, the state-of-the-art of detection for trichothecenes has gradually changed from gas chromatographic methods to liquid-chromatography coupled to mass spectrometry.

Professor Rudolph Krska, Ph.D.
Department for Agrobiotechnology (IFA-Tulln)
University of Natural Resources and Applied Life Sciences, Vienna
Tulln, Austria

Keywords: mycotoxins, cereals, food chain, animal feed, trichothecenes, chemical analysis, microbial reaction processes, metabolomics, water analysis, rapid test methods, regulation.

  



Special Topics : Mycotoxins : Professor Rudolf Krska - Special Topic of Mycotoxins