University of Minho School of Engineering Centre of Biological Engineering

Engenharia para a Qualidade de Vida: CIDADE – Semana da Escola de Engenharia -11 a 16 de Outubro de 2010

Introduction

In Portugal, maize (Zea mays L.) is the cereal that involves more agriculture explorations being a source of food, forage and processed products for industry. Fungal infection can result in mycotoxin contamination during growing, harvesting, storage, transport and processing (Chulze, 2010). Poor storage conditions of this commodity can expose it to factors such as high temperatures, condensation, insects and animals, leading to the reduction of its nutritional value, the development of toxigenic fungi and mycotoxin accumulation (Richard et al., 2009). To prevent fungal development it’s important to study the production chain. Aspergillus spp. are usually associated with this cereal during drying and storage (Samapundo et al. 2007), making it susceptible to mycotoxins such as aflatoxins, ochratoxins, cyclopiazonic acid and fumonisins.

The aim of this study was to evaluate the mycotoxigenic potential of isolated Aspergillus strains from maize samples and correlate it with the sampling place and weather conditions.

Author* CÉLIA SOARES

Supervisors: Armando Venâncio

* cmgsoares@deb.uminho.pt

THE ISOLATION OF ASPERGILLUS SPP FROM HARVESTED MAIZE IN THREE PORTUGUESE REGIONS

Results and Discussion

o It was possible to obtain, from a total of 132 samples, 1075 isolates from the gender Aspergillus and 732 of this isolates were tested for mycotoxins;

o Results show that there are differences between the incidence of the three groups of Aspergillus in the regions. Whereas in Elvas (Portalegre) and Riachos (Santarém) there is a high incidence of Aspergillus section Nigri, the same doesn't happens in Coimbra. This may be explained by the fact that black aspergilli are more resistant to the higher solar exposure and higher temperatures, typical of these regions (figure 2);

Results and Discussion

o A very small percentage of Aspergillus section Nigri are OTA producers even though they are abundant in the samples of two regions. However, there is the occurence of fumonisins B2 production by some strains;o Aspergillus section Flavi, are more common in the samples after leaving the dryers. They have been devided in three groups of species: A. flavus, A,parasiticus and A.tamarii. Most of A. flavus are producers of CPA as well as all A. tamarii. The only A. parasiticus isolate is producer of aflatoxins as expected for this species and less than 50% of A. flavus are producers of aflatoxins.

Materials and Methods

• The survey was carried out in three Portuguese regions between November 2008 and April 2009.

• The samples were collected from producers belonging to the National Producers Association of Maize and Sorghum (ANPROMIS – Associação Nacional de Produtores de Milho e de Sorgo):Cooperativa Agrícola de Coimbra (Coimbra); AGROMAIS (Riachos); CERSUL (Santa Eulália/Elvas).

• The sampling occurred in three distinct places of the storage chain (figure 1): reception; drying and expedition.

- Maize samples were plated in MEA10 (malt extract medium agar with 10% of NaCl) and the resulting fungi were isolated to MEA;

- Presence of mycotoxins was tested by high profile liquid chromatography (HPLC), by growing the Aspergillus spp. isolates in YES (for aflatoxins) and CYA (for OTA; CPA and Fumonisins)

Figure 1. Fluxogram of the storage chain.

Sampling at reception

Maize dryer

Storage in threshing-floor

Drying H= 14-16%

Storage in silo H=13-14%

Expedition

Reception of maize

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Figure 3. Number of Aspergillus spp. isolates obtained in the studied regions with the respective climate associated. A, B, C: number of isolates divided in distinct groups and their toxigenic potential, per region ( t = total of isolates).

Riachos has a micro-climate, typically continental with Mediterranean influences due to the proximity of Air Mountains, inducing a very dry and hot climate during summer time.

Coimbra climate is dominated by Atlantic influences with high precipitation values and moderate temperatures.

Elvas climate is dominated by Mediterranean influences, being very hot and dry during summer time.

Coimbra; 351

Elvas; 260

Riachos; 364

Conclusion

It is possible to correlate the climate with the kind of isolates obtained, being Aspergillus section Nigri associated with the regions of hotter and dryer climates. Aspergiilus section Flavi are very common in all regions even though they are more common after drying and storage. The great majority of fungi are not producers, but there is an alarming quantity of producers of aflatoxins and CPA.

The fact that this strains can produce mycotoxins in ideal conditions doesn’t mean necessarily that they can also produce in the original matrix (maize). Nevertheless, the mycotoxigenic potential of these fungi shouldn't be ignore because their occurrence means not only an health risk but also a big economical loss.

A

C

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Figure 2- Plates of MEA10 with 5 grains of maize. Fungal growth after 10 days at 250C

References

Chulze, S. N.,2010. 'Strategies to reduce mycotoxin levels in maize during storage: a review', Food Additives & Contaminants: Part A, 27: 5, 651 — 657 Richard, E., Heutte, N., Bouchart, V., Garon, D, 2009. Evaluation of fungal contamination and mycotoxin production in maize silage, Animal Feed Science and Technology 148: 309–320;Smapundo, S., Devlieghere,F., Geeraerd, A., Meulenaer, B., Impe, J. F., Debevere, J., 2007. Modelling of the individual and combined effects of water activity and temperature on the radial growth of Aspergillus flavus and A. parasiticus on corn, Food Microbiology 24:517-529

Acknowledgements• Célia Soares was supported by a grant from Fundação para a Ciência e Tecnologia (reference SFRH / BD / 37264 / 2007)

• The authors are grateful for the support and cooperation of ANPROMIS

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