Detection and detoxification of mycotoxins (Part Two)

Posted by beauty33 on December 2nd, 2021

In order to reduce or eliminate the various harms caused by mycotoxins, on the one hand, it is necessary to prevent and control the growth of molds and inhibit the production of mycotoxins from the source; on the other hand, it is necessary to continuously innovate and develop various detoxification methods. At present, common mycotoxin removal methods mainly include physical detoxification, chemical detoxification and biological detoxification. Physical detoxification mainly refers to adsorption and separation. Chemical detoxification is the use of chemical substances to change the structure of mycotoxins, and biological detoxification mainly refers to the enzyme adsorption and biodegradation of microorganisms.

The physical detoxification method mainly includes high temperature inactivation, adsorption method, water washing method, elimination method, and radiation method. The adsorption method is the most widely used method, and related adsorbents are divided into inorganic adsorbents and organic adsorbents according to their properties. Inorganic adsorbents include activated carbon, bentonite, attapulgite and montmorillonite. Montmorillonite is an aluminosilicate adsorbent, which is the most widely used adsorbent. The strongest mycotoxin adsorbent approved by the U.S. Food and Drug Administration (FDA) is a silica-alumina. Organic adsorbents are mainly functional carbohydrates found in yeast cells in recent years. Among them, glucomannan is a very effective adsorptive heteropolysaccharide, which is composed of β-D glucose and β-D mannose combined with β-1, 4 glycosidic bonds. Although the method of adsorption detoxification is simple and effective, the adsorption mechanism of the adsorbent needs to be further studied. The effect of adsorption is only transfer. If toxins need to be completely eliminated, further degradation is required. The adsorption effect of the adsorbent is mainly related to the type of adsorbent, the micropore size of the adsorbent, the charge distribution, the total amount of charge, the contact area, and the physical and chemical properties of the toxin.

Chemical detoxification is a detoxification method that achieves the detoxification effect by destroying the chemical structure of mycotoxins through some chemical reactions such as alkalization, hydrolysis, oxidation, reduction, etc. In the choice of existing detoxification methods, chemical methods are not the best choice. The main reason is that the addition of chemical reagents will cause certain nutrients in food or feed to be destroyed to a certain extent. There are many types of organic chemical reagents with good detoxification effects that have been studied, such as sodium humate, ozone and ammonia. Sodium humate is a weak organic acid salt, extracted from weathered coal, lignite, and peat. It contains more active groups such as hydroxyl, phenolic hydroxyl and carboxyl groups. Therefore, it has strong adsorption, exchange, complexation and chelation capabilities. Ozone is widely used for detoxification due to its advantages of green, environmental protection and safety. Due to its strong oxidizing properties, it can better oxidize mycotoxins and produce non-toxic oxidation products. However, the quality of food or feed may be affected. Ammonium or ammonia can also change the chemical structure of aflatoxin, thereby effectively degrading aflatoxin in feed.

Microbiological method has become a research hotspot nowadays because of its strong specificity, high efficiency, environmental protection, and avoidance of secondary pollution. It is considered to be the best way to detoxify food and feed. Microbial adsorption refers to the adsorption of mycotoxins by the microorganisms themselves (using a certain component or structure of the cell wall), mainly through the formation of a bacterial-toxin complex. Probiotics such as lactic acid bacteria in bacteria and yeasts in fungi have research applications in this regard. In the study of bacterial adsorption and detoxification, lactic acid bacteria are the most studied. Its detoxification mechanism is mainly through the physical adsorption of AFB1 by peptidoglycan with N-acetylmuramic acid and N-acetylglucosamine as the main components in the cell wall. Microorganisms are widely used because they can be used as food fermentation additives. Yeast cell walls contain special components such as mannan, glucan, chitin, etc., which can adsorb toxins. However, adsorption detoxification has certain drawbacks. First of all, because adsorption is mostly combined in a non-covalent manner, the specificity is not strong. The second is that the adsorption process is easily affected by the environment. Third, the bacteria-toxin complex formed after adsorption is difficult to be absorbed by the body, and the toxicity cannot be eliminated fundamentally.

Microbial degradation means that microorganisms use metabolites or secreted proteases to destroy the toxic structure of toxin molecules and produce non-toxic and harmless degradation products. Its degradation mechanism is mainly to destroy the toxic structural sites of mycotoxins. With the deepening and maturity of various researches, combined with modern molecular biology, genetic engineering and other technologies, many detoxification products of enzyme preparations have been produced accordingly. Extracted and purified from different microorganisms, detoxified enzyme preparations that can be used to degrade mycotoxins are obtained, which avoids the shortcomings of microbial adsorption and detoxification, and is safer, more efficient, environmentally friendly and highly specific.

In addition to detoxification enzymes, the fermentation broth of microorganisms has better degradation potential due to its rich ingredients, so the crude fermentation extract of microorganisms has become a new research hotspot and difficulty. The fermentation of microorganisms produces certain substances that can destroy the toxic structure of toxin molecules. At present, it has been discovered that the fermentation crude extracts of many bacteria and fungi can degrade mycotoxins, such as Streptomonas maltophilia, Bacillus subtilis, Chlamydomonas, Pseudomonas putida and other bacteria and pseudo armillaria, Aspergillus niger and other fungi, mainly through the enzymatic reaction mechanism of the crude fermentation extract to remove toxicity.

There are many types of mycotoxins, which are closely related to the health and production of humans and animals. We should grasp the key points, especially the severely harmful mycotoxins such as aflatoxin, zearalenone, and vomiting toxin, and establish high sensitivity, high specificity, fast and convenient detection method and a long-term monitoring mechanism of mycotoxins. Detoxification is a late-stage work in production. Judging from the existing research results, due to the various physical and chemical properties of various mycotoxin molecules, a single adsorbent cannot adsorb all mycotoxins, and it is in the adsorption of mycotoxins. At the same time, it also adsorbs the nutrients such as minerals and vitamins in the feed, so various detoxification methods are combined, and different adsorbents are adjusted in proportion to improve, and the composite mycotoxin with the advantages of high efficiency, broad spectrum and greenness is developed. Detoxification agents are the future development trend.

References

[1] Li CC, Yang WR. Research progress on the harm of mycotoxin in feed and its control methods: 2010 Shandong feed science and technology exchange conference [Z]. 2010.

[2] Bhatnagar D, Cleveland TE, Cotty PJ, et al. Mycological aspects of aflatoxin formation [Z]. 1993.

[3] Wu WD, Wang BJ, Can LF, et al. A study on the combined determination of gibberellone by TLC and HPLC [J]. Anim Husb Vet Med, 2010, 42(7):17–20.

[4] Pirouz AA, Selamat J, Iqbal SZ, et al. The use of innovative and efficient nanocomposite (magnetic graphene oxide) for the reduction on of Fusarium mycotoxins in palm kernel cake [J]. Sci Rep, 2017, 7(1): e12453

[5] Decontamination of aflatoxin B1-contaminated corn by ammonium persulphate during fermentation [J]. J Sci Food Agric, 2002, 82(5): 546–552

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