**Recent Trends in Microbiological Decontamination of Aflatoxins in Foodstuffs**

Carlos Augusto Fernandes Oliveira, Fernanda Bovo, Carlos Humberto Corassin, Alessandra Vincenzi Jager and Kasa Ravindranadha Reddy

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/51120

**1. Introduction**

Nowadays, about 100,000 fungi have already been identified. From these, more than 400 may be considered potentially toxigenic, and about 5% are known to produce toxic com‐ pounds or classes of compounds that cause adverse effects in animals and humans in sever‐ al parts of the world [1]. These compounds, called mycotoxins, are secondary metabolites of low molecular weight produced by mycelia or spores of filamentous fungi [2]. It is suggest‐ ed that mycotoxin production is generally limited to a relatively small number of mold spe‐ cies, and that toxin may be produced by the whole species or just one specific strain [3]. The more complex the synthesis pathway of a mycotoxin, the lesser the number of mold species that produce it.

The term "mycotoxin" originates from the Greek word "Mykes", meaning fungus, and from the Latin word "Toxicum", meaning poison or toxin [2]. Mycotoxins are classified as the most important chronic and noninfectious foodborne risk factor, more important than syn‐ thetic contaminants, plant toxins, food additives, and pesticide residues. Both humans and animals may show acute or chronic intoxication caused by mycotoxin ingestion, and the pathological condition that results from this ingestion is called mycotoxicosis [4]. Some fac‐ tors affect the magnitude of toxicity in humans or animals, including the animal species, mechanism of action, metabolism and defense mechanisms [5].

About 400 types of mycotoxins have been already discovered, and they are generally divid‐ ed into groups based on structural similarities and most important toxic effects [6]. From all

© 2013 Oliveira et al.; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2013 Oliveira et al.; licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

mycotoxins that have been isolated, aflatoxin is one of the most well-known and widely dis‐ tributed in foodstuffs, with proven and marked toxic properties. Aflatoxins are predomi‐ nantly produced by *Aspergillus flavus* and *A. parasiticus*, but may also be produced by other strains, such as *A. nomius, A. tamari*, and *A. pseudotamarii* [7]. Contamination of foodstuff with aflatoxigenic fungi may occur at any moment during production, harvesting, process‐ ing, transportation, and storage [8]. The most different kinds of foods may be affected, such as corn, peanuts, cotton seeds, rice, pistachio, almonds, chestnuts, Brazil nuts, and pumpkin seeds, as well as other oily seeds, such as sunflower and coconut [9].

physical methods have disadvantages, either because removal is not efficient, or because of high costs or nutritional losses to the product [16,17]. Biological methods are based on the action of microorganisms on mycotoxins. These microorganisms may be yeasts, filamentous fungi, bacteria, algae, among others, and their mechanisms of action is based on competition

Recent Trends in Microbiological Decontamination of Aflatoxins in Foodstuffs

http://dx.doi.org/10.5772/51120

61

Biodegradation of aflatoxins by microorganisms offers an attractive alternative for the con‐ trol or elimination of aflatoxins in foods and animal feed, preserving their quality and safety [19]. Besides, their use have a more "natural" appeal, given the ever-growing resistance of the consumer to chemical treatments [1]. Biological decontamination methods are being widely studied and may be a very promising choice, provided they show to be efficient, specific, cost-effective, and are environmentally friendly [20]. Among the types of microor‐ ganisms available and that may be used to remove aflatoxins from a contaminated medi‐ um, lactic acid bacteria (LAB) and yeasts are the most studied ones, showing the most

Therefore, the objective of this chapter was to present results of studies on microbiological methods for aflatoxin decontamination, more specifically on the ability of LAB and yeasts to

Nowadays, there are 18 similar compounds called aflatoxins. However, the most important types in terms of health and medical interest are identified based on their fluorescence un‐ der ultraviolet light (B = Blue and G = Green), such as aflatoxin B1 (AFB1), B2 (AFB2), G1 (AFG1) and G2 (AFG2). From these compounds, AFB1 is the most prevalent and toxic one [21]. When AFB1 is ingested by domestic animals in contaminated feed or foodstuffs, such as by dairy cows, the toxin undergoes liver biotransformation and is converted into aflatoxin M1 (AFM1), becoming the hydroxilated form of AFB1, which is excreted in milk, tissues and biological fluids of these animals [22-24]. It was reported that of all AFB1 ingested in feed, about 0.3% to 6.2% is transformed in AFM1 in milk and that there is a linear relationship be‐ tween the concentration of AFM1 in milk and the concentration of AFB1 in contaminated

Chronic exposure to low levels of aflatoxins represents a serious risk to economy, and main‐ ly to health [21]. Economic losses are related to decreased efficiency in industrial or agricul‐ tural production, with loss in quality, lower yield, and defective product [27]. It was also reported that in some states of the USA, economic losses to agriculture amount to 100 mil‐ lion dollars [19]. On the other hand, these losses caused by mold contamination and myco‐ toxins are greater than 1.6 billion dollars in the US, and African feeds lose about 670 billion

As for human and animal health, biological effects of aflatoxins may be carcinogenic, muta‐ genic, teratogenic, hepatotoxic, and immunosuppressive [29]. The International Agency for

dollars a year due to barriers to the trade of aflatoxin-contaminated foodstuffs [28].

by nutrients and space, interactions, and antibiosis, among others [18].

promising results.

degrade or sequestrate this mycotoxin.

feeds consumed by the animals [25,26].

**2. Toxicological Properties of Aflatoxins**

Aflatoxins are distributed worldwide. *Aspergillus* species are able to grow in a wide variety of substrates and under different environmental conditions. Toxin formation in agricultural products occurs in hot and humid weather, and in inadequate or deficient storage facilities. The most important factors that influence growth and aflatoxin production are relative hu‐ midity, ranging from 88 to 95% in most of the cases [8], and temperature, ranging from 36 to 38 C for mold growth, and 25 to 27 C for maximum toxin production [10].

Other factors may also influence aflatoxin production: substrate composition, water activity, pH, atmosphere (concentration of oxygen and carbon dioxide), microbial competition, me‐ chanical damage to the seeds, mold lineage, strain specificity and variation, instability of toxigenic properties, plant stress, insect infestation, and use of fungicides or fertilizers [2, 5, 11]. It is important to remember that aflatoxin contamination is cumulative, and the moment of harvesting and drying, and storage conditions may also play an important role in aflatox‐ in production [12].

Concerns related to the negative impacts of aflatoxins on health led to the study of strategies to prevent toxin formation in foodstuffs, as well as to eliminate, inactivate or reduce toxin bioavailability in contaminated products [13]. Contamination may be prevented by im‐ proved agricultural practices, antifungal agents, genetic engineering, and control of storage conditions [2]. Bioavailability may be reduced by enterosorption, which is done by adding nutritionally inert adsorbent compounds to the diet. These compounds are mycotoxin se‐ questrants, and prevent the toxin from being absorbed in the gastrointestinal tract of the ani‐ mals, making its distribution to the target organs impossible [14]. This method has limited practical use, due to the safety of the adsorbent agents used, and the difficulty in applying them to human foods [15]. Elimination or inactivation, that is, decontamination, may be ach‐ ieved by physical, chemical, and biological methods, which have to present the following characteristics: complete inactivation; destruction or removal of the toxin; no production or toxic residues in foods or no remainders of them; preservation of nutritional value and pal‐ atability of the food; destruction of fungal spores and mycelia to prevent production or reappearance of the toxin; no significant changes in the physical properties of the food; low cost and ease of use [1,11].

Physical methods for mycotoxin decontamination involve procedures such as thermal inac‐ tivation, ultraviolet light, ionizing radiation, or extraction with solvents. Chemical methods are based on agents that break mycotoxin structure, such as chlorine treatment (sodium hy‐ pochlorite or chlorine gas), oxidizing agents (hydrogen peroxide, ozone and sodium disul‐ fide), or hydrolytic agents (acids, alkalis and ammonia). However, both chemical and physical methods have disadvantages, either because removal is not efficient, or because of high costs or nutritional losses to the product [16,17]. Biological methods are based on the action of microorganisms on mycotoxins. These microorganisms may be yeasts, filamentous fungi, bacteria, algae, among others, and their mechanisms of action is based on competition by nutrients and space, interactions, and antibiosis, among others [18].

Biodegradation of aflatoxins by microorganisms offers an attractive alternative for the con‐ trol or elimination of aflatoxins in foods and animal feed, preserving their quality and safety [19]. Besides, their use have a more "natural" appeal, given the ever-growing resistance of the consumer to chemical treatments [1]. Biological decontamination methods are being widely studied and may be a very promising choice, provided they show to be efficient, specific, cost-effective, and are environmentally friendly [20]. Among the types of microor‐ ganisms available and that may be used to remove aflatoxins from a contaminated medi‐ um, lactic acid bacteria (LAB) and yeasts are the most studied ones, showing the most promising results.

Therefore, the objective of this chapter was to present results of studies on microbiological methods for aflatoxin decontamination, more specifically on the ability of LAB and yeasts to degrade or sequestrate this mycotoxin.
