Bioenzymatic detoxification of mycotoxins

Abstract

Mycotoxins are secondary metabolites produced during the growth, storage, and transportation of crops contaminated by fungi and are physiologically toxic to humans and animals. Aflatoxin, zearalenone, deoxynivalenol, ochratoxin, patulin, and fumonisin are the most common mycotoxins and can cause liver and nervous system damage, immune system suppression, and produce carcinogenic effects in humans and animals that have consumed contaminated food. Physical, chemical, and biological methods are generally used to detoxify mycotoxins. Although physical methods, such as heat treatment, irradiation, and adsorption, are fast and simple, they have associated problems including incomplete detoxification, limited applicability, and cause changes in food characteristics (e.g., nutritive value, organoleptic properties, and palatability). Chemical detoxification methods, such as ammonification, ozonation, and peroxidation, pollute the environment and produce food safety risks. In contrast, bioenzymatic methods are advantageous as they achieve selective detoxification and are environmentally friendly and reusable; thus, these methods are the most promising options for the detoxification of mycotoxins. This paper reviews recent research progress on common mycotoxins and the enzymatic principles and mechanisms for their detoxification, analyzes the toxicity of the degradation products and describes the challenges faced by researchers in carrying out enzymatic detoxification. In addition, the application of enzymatic detoxification in food and feed is discussed and future directions for the development of enzymatic detoxification methods are proposed for future in-depth study of enzymatic detoxification methods.

Keywords: degradation; detoxification; enzymes; fungi; mechanism; mycotoxins.

Figure 1

The flow direction of mycotoxins in foods. AFB₁, Aflatoxin B₁; ZEN, Zearalenone; DON, Deoxynivalenol; OTA, Ochratoxin; PAT, Patulin; and FB₁, Fumonisin B₁.

Figure 2

(A) Structural formula of AFB₁ and its derivatives. The red group is the detoxifying enzyme action group and the green group shows the difference between AFB₁ derivatives and them. AFB₁, Aflatoxin B₁; AFB₂, Aflatoxin B₂; AFG₁, Aflatoxin G₁; AFG₂, Aflatoxin G₂. (B) Main degradation and transformation products of AFB₁. (C) Structure of the active center of laccase. (D) Detoxification of AFB₁ by CotA laccase. (E) Degradation of AFB₁ by AFO. (F) Degradation of AFB₁ by BacC. (G) Degradation of AFB₁ by FDRs. (H) Degradation of AFB₁ by ATTM.

Figure 3

(A) Structural formula of ZEN and its derivatives. The red group is the detoxifying enzyme action group and the green group shows the difference between ZEN derivatives and them. ZEN, Zearalenone; β-estradiol; α-ZOL, α-Zearalenol; β-ZOL, β-Zearalenol; ZAN, Zearalanone; α-ZAL, α-Zearalanol; β-ZAL, β-Zearalanol. (B) Main degradation and transformation products of ZEN. (C) Degradation of ZEN by lactonase. (D) Degradation by monooxygenase and carboxylester hydrolase. (E) Degradation of ZEN by StDyP. (F) Degradation of ZEN by PoDyP4. (G) Degradation of ZEN by SHP. (H) Degradation of ZEN by FSZ. (I) Degradation of ZEN by ZenH.

Figure 4

(A) Structural formula of DON and its corresponding detoxification enzyme action groups. The red group is the detoxifying enzyme action group. (B) Main degradation and transformation products of DON. (C) Degradation of DON by dehydrogenase and reductase. (D) Degradation of DON and its derivatives by SPG. (E) Degradation of DON by the enzyme encoded by DLK06_RS13370. (F) Degradation of DON by D-G6.

Figure 5

(A) Structural formula of OTA and its derivatives. The red group is the detoxifying enzyme action group and the green group shows the difference between OTA derivatives and them. OTA, Ochratoxin A; OTB, Ochratoxin B; and OTC, Ochratoxin C. (B) Main degradation transformation products of OTA. (C) Degradation of OTA by carboxypeptidase.

Figure 6

(A) Structural formula of PAT (patulin) and its corresponding detoxification enzyme action groups. The red group is the detoxifying enzyme action group. (B) Main degradation transformation products of PAT. (C) Degradation of PAT by PPL. (D) Possible degradation of PAT by PLE, HRP, LA, and LM. (E) Degradation of PAT by oxidoreductases.

Figure 7

(A) Structural formula of FB₁ (fumonisin B₁) and its corresponding detoxification enzyme action groups. The red group is the detoxifying enzyme action group. (B) Main degradation transformation products of FB₁.

Figure 8

(A) Chemical structural formula of Sterigmatocystin, Gliotoxin, and Citrinin. (B) Degradation of AFB₁ and ZEN by MnP. (C) Degradation of AFB₁, ZEN, and DON by BsDyP.