3. Microbiological control of AFB1

To date, many physical and chemical methods have been used to detoxify AFB1; however, only a few of these methods are in practical use, probably due to difficulties in complying with the FAO requirements: reduction of AFB1 without residual toxicity, guarantee of nutritional values, and no modification of food or feed properties [58, 59]. Since cost-effective methods to detoxify mycotoxin-contaminated grains and foods are urgently needed to minimize potential losses to the farmer and toxicological hazards to the consumer [60], finding of new and suitable methods for AFB1 decontamination has become a primary need.

most studied, due largely to their GRAS character and because they have shown to have several potential applications against AFB1 both in vitro and in vivo [72–75]. Probiotics are living microorganisms that when administered in adequate amounts confer a health benefit to the host directly or indirectly through the maintenance of the microbial balance in their digestive tract [65, 76]. Several bacterial genera have been used as probiotics in livestock, including many species of Bacillus, Bifidobacterium, Enterococcus, E. coli, Lactobacillus, Lactococcus, and Streptococcus, although some species of molds and yeasts, such as Aspergillus, Candida, and

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In poultry industry, probiotics have been reported to have a beneficial effect on performance, modulation of intestinal microflora and pathogen inhibition, intestinal histological changes, immunomodulation, certain hematobiochemical parameters, improving sensory characteristics of dressed meat, and promoting microbiological meat quality [79, 80]. In addition, probiotic bacteria may possess antimutagenic and anticarcinogenic activity. The mechanisms of these activities remain unclear; however, alteration of fecal bacterial enzyme activities associated with conversion of promutagens and procarcinogens to ultimate carcinogens and binding

Three possible mechanisms have been proposed by which probiotics can counteract the toxic effects of AFB1: (1) competing with aflatoxigenic mold strains for space, occupying the same ecological niche or using nutrients, and thus reducing AFB1 biosynthesis; (2) encouraging AFB1 metabolic degradation by enzymes, or (3) impeding its intestinal absorption by AFB1

It has been suggested by in vitro studies that probiotics can inhibit AFB1 production through releasing metabolites to the media, such as organic acids, bacteriocins, and even hydrogen peroxide, which may interfere with AFB1 biosynthesis [82, 83]. Other alternative could be the reduction or inhibition in the growth of aflatoxigenic mold strains caused by a decrease in pH of the media and/or a nutrient competition of the culture media, which could also have contributed to the removal of AFB1 [84–87]. In Figure 1, it is shown how some probiotics from the lactobacilli strains can decrease both AFB1 production and the growth rate of an

Although several bacterial strains have been used as biocompetitive agents of aflatoxigenic mold strains, some of them become inactive under extreme conditions of humidity and temperature, so that not all probiotic strains are ideal for this application. In this sense, studies on the prevention of AFB1 contamination using highly competitive non-toxigenic strains of A. parasiticus and A. flavus have shown certain advantages, which implies that these mold strains may be potentially useful as agents directed at competitively excluding toxigenic strains [88]. The other mechanism that the probiotics have to counteract the toxic effects of AFB1 is through its metabolic degradation or biodegradation, which can be defined as the degradation or enzymatic transformation of the mycotoxin to less or non-toxic compounds. Biodegradation using microorganisms or their enzymes is one of the most studied strategies for AFB1 management; this method has been actively studied and can be a highly promising choice, since it is efficient, specific, and environmentally friendly to reduce or eliminate the possible contaminations of

Saccharomyces, have also been used [77, 78].

of dietary mutagens and carcinogens has been proposed [81].

binding onto the cell walls of the probiotics strains.

aflatoxigenic mold strain.

In this sense, microbiological control approach has taken strength in the field of research to control AFB1. Researchers have focused on biological treatments for detoxification mainly through two mechanisms: adsorption and degradation, both of which can be achieved by biological systems such as bacteria, yeasts, molds, actinomycetes, and algae [61].

Biological adsorption can occur either by attaching the AFB1 to the cell wall components of the microorganisms or by active internalization and accumulation. Also, dead microorganisms can absorb AFB1, and this phenomenon can be exploited in the creation of biofilters for fluid decontamination or probiotics to bind and remove the AFB1 from the intestine [62]. However, biological adsorption mechanism is naturally reversible, and AFB1 may be easily released, so that it is necessary to search for novel approaches to overcome these drawbacks, as for example the combination of mineral and biological adsorbents to improve their effectiveness [63].

On the other hand, microbiological biodegradation is performed by either extracellular or intracellular enzymes, so the degradation is generally permanent and irreversible which can alter, reduce, or completely eradicate AFB1 toxicity [30]. Nevertheless, modification of AFB1 structure can result in other molecules, such as aflatoxicol (AFL), also with potential toxic effects [64]. Thus, further knowledge is needed on the identification, quantity, and toxicity of degradation metabolites prior to the potential applications of biological treatments [59].

Microbiological control seems to be becoming one of the most promising approaches for AFB1 control; since the last four decades, the use of microorganisms is one of the well-known strategies for the management of AFB1 in foods and feeds. These methods of bioadsorption and biodegradation are being actively studied and can be a highly promising choice because they are efficient, specific, and environmentally friendly [65–68].
