Biodetoxification
Using enzymes to neutralize mycotoxins

Mycotoxins are toxic metabolites produced by fungi, which can cause both acute and chronic diseases in humans and animals.

They are lipophilic molecules primarily absorbed in the gut and later distributed to fat and other soft tissues, leading to kidney and liver damage.

The International Agency for Research on Cancer (IARC) has classified some mycotoxins, such as aflatoxins, fumonisins, and ochratoxins, as Group 2B carcinogens.

Mycotoxins also contaminate crops such as cereals, nuts, seeds, vegetables, and fruits, causing significant losses in the agricultural sector.

The Food and Agriculture Organization (FAO) estimates that 25 % of global agricultural crops are affected by mycotoxins (Eskola et al., 2020).

Over time, mycotoxins have received considerable attention, especially over the last three decades and, as a result, the field of mycotoxicology is gaining more importance due to its toxicological effects (Sreenivasa et al., 2008 y 2011).

Mycotoxicosis is the illness caused by the consumption of mycotoxins by humans and animals through toxin-contaminated food and feed, which can lead to immune suppression and, even, cancer.

Additionally, mycotoxin intoxication in livestock results in significant economic losses in the meat industry (Nagaraja, 2016).

To decontaminate mycotoxins, various detoxification methods are employed, including physical, chemical, and biological strategies (Deepa & Sreenivasa, 2019).

• ⇰ Physical methods, such as heat treatment and adsorption, are quick but may affect the quality and nutritional value of food.
• ⇰ Chemical techniques, such as ammonification and ozonation, are effective but can pose food safety risks.

To address these challenges, biological detoxification has emerged as a viable alternative, utilizing microorganisms and their products. Additionally, enzymatic degradation presents a promising strategy for selective detoxification, offering an eco-friendly, reusable, and effective solution.

This method ensures safety for human and animal health while supporting sustainable agricultural practices (Deepa et al., 2017).

Mycotoxins and their properties

Mycotoxins are classified into various groups based on:

• Chemical structure
• Biological activity
• Fungi responsible for their production

An outline of their classification and toxicological effects is listed in Table 1.

Enzymatic degradation mechanisms

Currently, biological degradation strategies have gained more popularity over physical and chemical methods.

The biological degradation of mycotoxins involves active metabolites secreted by microorganisms which alter the structure of mycotoxins, converting them into less toxic or non-toxic products (Figure 1).

Enzymatic degradation of mycotoxins offers various advantages over microbial degradation, including high specificity, efficiency, performance, and ease of implementation (Ji et al., 2016).

These mycotoxin-degrading enzymes provide a major advantage over other detoxification methods by ensuring the safe and effective removal of these harmful substances.

The degradation of mycotoxins can occur either extracellularly or intracellularly (Figure 2).

• ⇰ Extracellular degradation involves the release of enzymes or metabolites by microorganisms that break down mycotoxins outside the cell.
• ⇰ Intracellular degradation occurs when microorganisms absorb mycotoxins, and enzymes inside the cell modify or degrade these compounds.

Both processes contribute to mycotoxin detoxification, with extracellular degradation often being faster and more efficient in some cases.

A list of enzymes that degrade mycotoxins is provided in Table 2.

Recent research has focused on identifying and developing effective enzymatic strategies for mycotoxin degradation, aiming to mitigate their impact on food and feed safety.

Various enzymes from microorganisms and fungi have shown promising results in breaking down aflatoxins into less toxic compounds, offering environmentally friendly and efficient detoxification methods.

Aflatoxin degradation

Several notable studies have demonstrated the potential of enzymatic degradation, highlighting different sources of aflatoxin-degrading enzymes and their mechanisms of action.

• A strategy was developed to express an aflatoxin-degrading enzyme from the edible honey mushroom Armillariella tabescens in developing maize kernels, effectively controlling aflatoxin contamination under harvest conditions ( (Schmidt et al., 2021).
• Ligninolytic enzymes from spent mushroom substrate (SMS), a by-product of edible mushroom cultivation, demonstrated over 90 % degradation of aflatoxin B1 (AFB1) after seven days, with optimal degradation occurring at pH 8 (Brana et al., 2019).

• The extracellular enzyme MADE (Mycobacteria Aflatoxin Degradation Enzyme), isolated from Myxococcus fulvus ANSMO68, has shown high efficacy in degrading aflatoxins B1, G1, and M1, achieving 72 % degradation of AFB1, 68 % of AFG1, and 64 % of AFM1 after 48 hours (Zhao et al., 2010).
• The dye-decoloring peroxidase (Dyp) from Bacillus subtilis SCK6, expressed in E. coli, efficiently degraded aflatoxin B1 in the presence of Mn²⁺ (Qin et al., 2021).

Ochratoxin degradation

Enzymatic strategies have also been explored for the breakdown of ochratoxins, another group of mycotoxins of major concern in food and feed safety.

Several studies have investigated the potential of fungal and plant-derived enzymes to degrade ochratoxin A (OTA) efficiently, highlighting their application in sustainable detoxification approaches.

• A study on exoenzymes from Trichoderma afroharzianum strain T22, or its peroxidase supplementation, demonstrated significant degradation of both aflatoxin B1 and ochratoxin A, providing a sustainable method for detoxifying mycotoxin-contaminated food and feed (Dini et al., 2022).
• The commercial peroxidase enzyme (POD) from Armoracia rusticana was evaluated for its ability to degrade both ochratoxin A (OTA) and zearalenone (ZEN), achieving 27 % and 48 % degradation of OTA and ZEN, respectively, in beer after 6 hours (Garcia et al., 2020).

Zearalenone degradation

In addition to aflatoxins and ochratoxins, zearalenone (ZEN) is another mycotoxin of significant concern, particularly due to its estrogenic effects in livestock.

Research has focused on enzymatic approaches to degrade ZEN efficiently, with promising results from both recombinant and plant-derived enzymes.

• A recombinant fusion enzyme, combining zearalenone hydrolase (ZHD) and carboxypeptidase (CP), was developed to achieve 100 % degradation of ZEN within 2 hours at pH 7 and 35 °C. In contrast, CP alone degraded only 60 % of ZEN in 28 hours. The combination of ZHD-CP and CP also achieved 100 % degradation of OTA in just 30 minutes (Azam et al., 2019).
• Armoracia rusticana exhibited substantial ZEN degradation, reaching 64.9 % degradation in a model solution after 6 hours (Garcia et al., 2020).

Fumonisin degradation

Fumonisins are another group of mycotoxins of concern, particularly due to their impact on animal health and their association with diseases such as leukoencephalomalacia in horses and pulmonary edema in pigs.

Recent research has explored bacterial strains and enzymatic mechanisms capable of degrading fumonisins effectively.

• Recombinant carboxylesterase was used to catalyse the deesterification of fumonisin B1 to hydrolysed fumonisin B1. When supplemented at 60 U/kg, this enzyme significantly reduced fumonisin B1 levels in turkeys and pigs (Masching et al., 2016). This suggests that recombinant enzymes have potential for detoxifying fumonisin-contaminated feed and food.
• Carboxylesterases and aminotransferases have been used to synergistically degrade fumonisins.

Deoxynivalenol degradation

Deoxynivalenol (DON), also known as vomitoxin, is a mycotoxin commonly found in cereals, posing a significant risk to animal health and feed safety.

Recent studies have focused on enzymatic and microbial strategies to degrade or detoxify DON, converting it into less toxic compounds.

• A novel bacterial strain, Pelagibacterium halotolerans ANSP101, isolated from seawater, successfully transformed DON into the less toxic 3-keto-deoxynivalenol by oxidizing the C3 hydroxyl group. This DON-degrading activity was attributed to intracellular proteins, with optimal degradation occurring in cereals and feed (Zhang et al., 2020).
• Dehydrogenases, reductases, glyoxalases, and acyltransferases have been effectively used to detoxify or convert DON into non-toxic intermediates.

CONCLUSION

In conclusion, the widespread contamination of food and feed by mycotoxins has drawn global attention.

Various strategies have been developed to mitigate this issue, including physical and chemical methods, with biological detoxification emerging as a safe and effective alternative.

The use of microorganisms for mycotoxin detoxification represents a promising approach for the food and feed industries, particularly through enzymatic degradation.

This method is valued for its specificity, effectiveness, environmental friendliness, and safety.

Specific enzymes play a crucial role in converting toxic mycotoxins into less harmful or non-toxic compounds.

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