**2. Toxicological Properties of Aflatoxins**

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

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

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‐

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

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

seeds, as well as other oily seeds, such as sunflower and coconut [9].

60 Aflatoxins - Recent Advances and Future Prospects

38 C for mold growth, and 25 to 27 C for maximum toxin production [10].

in production [12].

cost and ease of use [1,11].

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 feeds consumed by the animals [25,26].

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

As for human and animal health, biological effects of aflatoxins may be carcinogenic, muta‐ genic, teratogenic, hepatotoxic, and immunosuppressive [29]. The International Agency for Research on Cancer classifies AFB1 and AFM1 as Group 1 human carcinogens, even though AFM1 is about 10 times less carcinogenic than AFB1 [30]. All these aflatoxin effects are influ‐ enced by variations according to the animal species, sex, age, nutritional status, and effects of other chemical products, besides the dose of toxin and the length of exposure of the or‐ ganism to it [31].

**3. Decontamination of Aflatoxins by Lactic Acid Bacteria**

teria, besides increasing shelf life and sensory properties of these foods [ 23].

products of metabolism, such as hydrogen peroxide or bacteriocins [37].

the ability to remove mycotoxins from the medium, reducing their effects.

as food additives without compromising the characteristics of the final product.

LAB is a large group of genetically different bacteria that, besides producing lactic acid as the main product of their metabolism, have similar characteristics: they are all gram-posi‐ tive, non-sporoformers, non-motile, and catalase, and oxidase negative. They are, therefore, aerotolerant anaerobes. Besides, they mandatorily ferment sugars and tend to be nutritional‐ ly fastidious, frequently requiring specific amino acids and B-complex vitamins as growth factors [34]. Several LAB genera, such as *Lactobacillus*, *Bifidobacterium* and *Lactococcus* are known for they ability to act as preserving agents in fermented foods, such as vegetables, cereals, dairy and meat products, actively inhibiting spoilage and growth of pathogenic bac‐

Recent Trends in Microbiological Decontamination of Aflatoxins in Foodstuffs

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

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Fermentation enables longer shelf life and improves sensory and nutritional properties of the product, as sugar fermentation lowers pH and inhibits growth of spoilage and patho‐ genic microorganisms. Fermentation is also responsible for other reactions, such as proteins hydrolysis, improving texture and flavor; synthesis of aromatic components and texturizers, affecting the consistency of the product; and production of inhibitory components [35,36]. This inhibition is, in part, caused by the final products of fermentation, such as lactic acid, diacetyl, acetaldehyde and acetic acid, which may accumulate in inhibitory concentrations in certain foods and drinks. In other cases, inhibition may also be caused by secondary by-

Therefore, two aspects may be considered when LAB are used: fermentation and antibiosis ability. In the first case, the starter culture added to the food acts on the substrate, causing advantages to the food. In the second case, the starter culture has to inhibit the development of undesirable microorganisms that may spoil the product or be hazardous to human health. In reference [38], authors state that one of the effects that were identified in LAB was protec‐ tion against toxins found in foods, such as heterocyclic amines, polycyclic aromatic hydro‐ carbons, reactive oxygen species, and mycotoxins. In the latter case, studies have demonstrated that LAB have the ability to inhibit aflatoxin biosynthesis, or that they have

It should be emphasized that with increased interest in probiotic food production all over the world, selection of LAB cultures with probiotic characteristics and greater ability to re‐ move mycotoxins may help to reduce risk of exposure to these toxins in foodstuffs, which is a very promising line of research in mycotoxicology. Yeast and LAB strains have great abili‐ ty to remove mycotoxins, and may be used as part of starter cultures in the fermentation of foods and drinks [39]. These microorganisms have, thus, ability to ferment and decontami‐ nate the medium, and purified components of these strains may be used in small amounts

One of the first studies in this area was carried out in the 1960s, when these authors evaluat‐ ed the ability of about 1,000 types of microorganisms to degrade aflatoxins [40]. Yeasts, fila‐ mentous fungi, bacteria, actinomycetes, algae, and fungal spores were among the organisms studied. From these, only the bacterium *Flavobacterium aurantiacum* B-184 (known today as *Nocardia corynebacterioides*) was able to irreversibly remove aflatoxins from the solution.

Aflatoxicosis is the poisoning caused by the ingestion of moderate to high levels of alfatoxin in contaminated foods. Acute aflatoxicosis causes quick and progressive jaundice, edema of the limbs, pain, vomiting, necrosis, cirrhosis and, in severe cases, acute liver failure and death, caused by the ingestion of about 10 to 20 mg of aflatoxin in adults. Aflatoxin LD50 shows the following order of toxicity: AFB1> AFM1> AFG1> AFB2> AFG2 [4, 32]. Chronic afla‐ toxicosis causes cancer, immunosuppression and other pathological conditions, having the liver as the primary target organ [4].

The greatest risk presented by aflatoxins for human beings is chronic exposure causing hep‐ atocellular carcinoma, which may be made worse by hepatitis A virus [5]. It was also report that aflatoxins were found in the tissues of children affected by Reye syndrome (encephal‐ opathy with serious lesions in liver and kidneys after influenza or chickenpox), and Kwa‐ shiorkor (protein-energy malnutrition). Aflatoxicosis is considered, then, a contributing factor to these diseases.

AFB1 is metabolized in the liver by the cytochrome P450 system, generating its most carcino‐ genic metabolite, AFB1-8,9-epoxide (AFBO), or other less mutagenic forms, such as AFM1, Q1 or P1. There are several pathways for AFBO after it is metabolized, with one of them leading to cancer, another to toxicity and another one, to excretion. AFBO exo-form easily binds to cell macromolecules, including genetic material such as DNA proteins, producing adducts. Formation of these DNA adducts leads to genetic mutations and cancer, and their excretion in the urine of infected people is not only a proof that humans have the necessary biochemi‐ cal pathways for carcinogenesis, but also offers a reliable biomarker for AFB1 exposure [24].

Potential risk to human health caused by aflatoxins has led to surveillance programs for the toxin in different raw materials, as well as regulations determined by almost every country in the world [9]. A study carried out by the Food and Agriculture Organization of the Unit‐ ed Nations (FAO) in 2002 pointed out that about 100 countries had specific regulations for the presence of aflatoxin in foods, dairy products and animal feed, and that the total popula‐ tion of these countries amounted to 90% of the world population. The same study showed that regulations for aflatoxin are getting more diverse and detailed, including sampling methods and methods of analysis [33].

In countries where a regulation for aflatoxin exists, tolerance levels for the total aflatoxin (sum of aflatoxins B1, B2, G1 and G2) ranges from 1 to 35 µg/kg for foods, with an average of 10 g/kg; and from zero to 50 µg/kg for animal feed, with an average of 20 µg/kg. For AFM1 in milk, tolerance levels are between 0.05 and 0.5 µg/kg, with most countries adopting a threshold of 0.05 µg/kg [10].
