The Potential of Peroxidases Extracted from the Spent Mushroom (Flammulina velutipes) Substrate Significantly Degrade Mycotoxin Deoxynivalenol

Theoretical insights into the mechanism underlying aflatoxin B1 transformation by the BsCotA-methyl syringate system

Global concern exists regarding the contamination of food and animal feed with aflatoxin B1 (AFB1), which poses a threat to the health of both humans and animals. Previously, we found that a laccase from Bacillus subtilis (BsCotA) effectively detoxified AFB1 in a reaction mediated by methyl syringate (MS), although the underlying mechanism has not been determined. Therefore, our primary objective of this study was to explore the detoxification mechanism employed by BsCotA. First, the enzyme and mediator dependence of AFB1 transformation were studied using the BsCotA-MS system, which revealed the importance of MS radical formation during the oxidation process. Aflatoxin Q1 (AFQ1) resulting from the direct oxidation of AFB1 by BsCotA, was identified using ultra-high-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The results of UPLC-MS/MS and density functional theory calculations indicated that the products included AFQ1, AFB1-, and AFD1-MS-coupled products in the BsCotA-MS system. The toxicity evaluations revealed that the substances derived from the transformation of AFB1 through the BsCotA-MS mechanism exhibited markedly reduced toxicity compared to AFB1. Finally, we proposed a set of different AFB1-transformation pathways generated by the BsCotA-MS system based on the identified products. These findings greatly enhance the understanding of the AFB1-transformation mechanism of the laccase-mediator system.

DypB peroxidase for aflatoxin removal: New insights into the toxin degradation process

Aflatoxin B1 (AFB1) is one of the most potent carcinogens and a widespread food and feed contaminant. As for other toxins, many efforts are devoted to find efficient and environmentally-friendly methods to degrade AFB1, such as enzymatic treatments, thus improving the safety of food and feed products. In this regard, the dye decolorizing peroxidase of type B (DypB) can efficiently degrade AFB1. The molecular mechanism, which is required to drive protein optimization in view of the usage of DypB as a mycotoxin reduction agent in large scale application, is unknown. Here, we focused on the role of four DypB residues in the degradation of AFB1 by alanine-scanning (residues 156, 215, 239 and 246), which were identified from biochemical assays to be kinetically relevant for the degradation. As a result of DypB degradation, AFB1 is converted into four products. Interestingly, the relative abundancy of these products depends on the replaced residues. Molecular dynamics simulations were used to investigate the role of these residues in the binding step between protein and manganese, a metal ion which is expected to be involved in the degradation process. We found that the size of the haem pocket as well as conformational changes in the protein structure could play a role in determining the kinetics of AFB1 removal and, consequently, guide the process towards specific degradation products.

Global distribution, toxicity to humans and animals, biodegradation, and nutritional mitigation of deoxynivalenol: A review

Deoxynivalenol (DON) is one of the main types of B trichothecenes, and it causes health-related issues in humans and animals and imposes considerable challenges to food and feed safety globally each year. This review investigates the global hazards of DON, describes the occurrence of DON in food and feed in different countries, and systematically uncovers the mechanisms of the various toxic effects of DON. For DON pollution, many treatments have been reported on the degradation of DON, and each of the treatments has different degradation efficacies and degrades DON by a distinct mechanism. These treatments include physical, chemical, and biological methods and mitigation strategies. Biodegradation methods include microorganisms, enzymes, and biological antifungal agents, which are of great research significance in food processing because of their high efficiency, low environmental hazards, and drug resistance. And we also reviewed the mechanisms of biodegradation methods of DON, the adsorption and antagonism effects of microorganisms, and the different chemical transformation mechanisms of enzymes. Moreover, nutritional mitigation including common nutrients (amino acids, fatty acids, vitamins, and microelements) and plant extracts was discussed in this review, and the mitigation mechanism of DON toxicity was elaborated from the biochemical point of view. These findings help explore various approaches to achieve the best efficiency and applicability, overcome DON pollution worldwide, ensure the sustainability and safety of food processing, and explore potential therapeutic options with the ability to reduce the deleterious effects of DON in humans and animals.

Deoxynivalenol: Emerging Toxic Mechanisms and Control Strategies, Current and Future Perspectives

Deoxynivalenol (DON) is the most frequently present mycotoxin contaminant in food and feed, causing a variety of toxic effects in humans and animals. Currently, a series of mechanisms involved in DON toxicity have been identified. In addition to the activation of oxidative stress and the MAPK signaling pathway, DON can activate hypoxia-inducible factor-1α, which further regulates reactive oxygen species production and cancer cell apoptosis. Noncoding RNA and signaling pathways including Wnt/β-catenin, FOXO, and TLR4/NF-κB also participate in DON toxicity. The intestinal microbiota and the brain-gut axis play a crucial role in DON-induced growth inhibition. In view of the synergistic toxic effect of DON and other mycotoxins, strategies to detect DON and control it biologically and the development of enzymes for the biodegradation of various mycotoxins and their introduction in the market are the current and future research hotspots.

Analysis of RIOK2 Functions in Mediating the Toxic Effects of Deoxynivalenol in Porcine Intestinal Epithelial Cells

Deoxynivalenol (DON) is a type of mycotoxin that threatens human and livestock health. Right open reading frame kinase 2 (RIOK2) is a kinase that has a pivotal function in ribosome maturation and cell cycle progression. This study aims to clarify the role of the RIOK2 gene in DON-induced cytotoxicity regulation in porcine intestinal epithelial cells (IPEC-J2). Cell viability assay and flow cytometry showed that the knockdown of RIOK2 inhibited proliferation and induced apoptosis, cell cycle arrest, and oxidative stress in DON-induced IPEC-J2. Then, transcriptome profiling identified candidate genes and pathways that closely interacted with both DON cytotoxicity regulation and RIOK2 expression. Furthermore, RIOK2 interference promoted the activation of the MAPK signaling pathway by increasing the phosphorylation of ERK and JNK. Additionally, we performed the dual-luciferase reporter and ChIP assays to elucidate that the expression of RIOK2 was influenced by the binding of transcription factor Sp1 with the promoter region. Briefly, the reduced expression of the RIOK2 gene exacerbates the cytotoxic effects induced by DON in IPEC-J2. Our findings provide insights into the control strategies for DON contamination by identifying functional genes and effective molecular markers.

Can Red Yeast (Sporidiobolus pararoseus) Be Used as a Novel Feed Additive for Mycotoxin Binders in Broiler Chickens?

Mycotoxin-contaminated feeds may negatively affect broiler chickens’ health; hence, a sustainable approach to achieve mycotoxin elimination is necessary. This study aimed to evaluate the efficacy of red yeast (Sporidiobolus pararoseus; RY) as a novel mycotoxin binder in broilers. A total of 1440 one-week-old male broiler chicks were randomly assigned to 12 treatments in a 3 × 4 factorial design. The dietary treatments included three levels of mycotoxin-contaminated diets (0 µg kg−1 (0% of mycotoxin; MT), 50 µg kg−1 (50% MT), and 100 µg kg−1 (100% MT)) and four levels of mycotoxin binders (0.0 and 0.5 g kg−1 commercial binder, and 0.5 and 1.0 g kg−1 RY). Experimental diets were contaminated with aflatoxin B1, zearalenone, ochratoxin A, T-2 toxin, and deoxynivalenol in the basal diet. Furthermore, the parameters including feed intake, body weight, and mortality rate were recorded on a weekly basis. After feeding for 28 days, blood and organ samples were collected randomly to determine the blood biochemistry, relative organ weights, and gut health. The results indicated that mycotoxin-contaminated diets reduced the average daily weight gain (ADG), villus height (VH), and villus height per the crypt depth ratio (VH:CD) of the intestine, as well as the population of Lactobacillus sp. and Bifidobacterium sp. in the cecal (p < 0.05), whereas they increased the mycotoxins concentration in the blood samples and the apoptosis cells (TUNEL positive) in the liver tissue (p < 0.01) of broiler chicken. In contrast, RY-supplemented diets had better ADG values and lower chicken mortality rates (p < 0.05). Moreover, these combinations positively impacted the relative organ weights, blood parameters, bacteria population, intestinal morphology, and pathological changes in the hepatocytes (p < 0.05). In conclusion, RY supplementation effectively alleviated the toxicity that is induced by AFB1 and OTA, mainly, and could potentially be applied as a novel feed additive in the broiler industry.

Improved Foods Using Enzymes from Basidiomycetes

Within the kingdom of fungi, the division Basidiomycota represents more than 30,000 species, some with huge genomes indicating great metabolic potential. The fruiting bodies of many basidiomycetes are appreciated as food (“mushrooms”). Solid-state and submerged cultivation processes have been established for many species. Specifically, xylophilic fungi secrete numerous enzymes but also form smaller metabolites along unique pathways; both groups of compounds may be of interest to the food processing industry. To stimulate further research and not aim at comprehensiveness in the broad field, this review describes some recent progress in fermentation processes and the knowledge of fungal genetics. Processes with potential for food applications based on lipases, esterases, glycosidases, peptidases and oxidoreductases are presented. The formation and degradation of colourants, the degradation of harmful food components, the formation of food ingredients and particularly of volatile and non-volatile flavours serve as examples. In summary, edible basidiomycetes are foods—and catalysts—for food applications and rich donors of genes to construct heterologous cell factories for fermentation processes. Options arise to support the worldwide trend toward greener, more eco-friendly and sustainable processes.

Invited review: Remediation strategies for mycotoxin control in feed

Mycotoxins are secondary metabolites of different species of fungi. Aflatoxin B1 (AFB1), deoxynivalenol (DON), zearalenone (ZEN) and fumonisin B1 (FB1) are the main mycotoxins contaminating animal feedstuffs. These mycotoxins can primarily induce hepatotoxicity, immunotoxicity, neurotoxicity and nephrotoxicity, consequently cause adverse effects on the health and performance of animals. Therefore, physical, chemical, biological and nutritional regulation approaches have been developed as primary strategies for the decontamination and detoxification of these mycotoxins in the feed industry. Meanwhile, each of these techniques has its drawbacks, including inefficient, costly, or impractically applied on large scale. This review summarized the advantages and disadvantages of the different remediation strategies, as well as updates of the research progress of these strategies for AFB1, DON, ZEN and FB1 control in the feed industry.

Efficient Degradation of Aflatoxin B1 and Zearalenone by Laccase-like Multicopper Oxidase from Streptomyces thermocarboxydus in the Presence of Mediators

Multicopper oxidases (MCOs) are a diverse group of enzymes that could catalyze the oxidation of different xenobiotic compounds, with simultaneous reduction in oxygen to water. Aside from laccase, one member of the MCO superfamily has shown great potential in the biodegradation of mycotoxins; however, the mycotoxin degradation ability of other MCOs is uncertain. In this study, a novel MCO-encoding gene, StMCO, from Streptomyces thermocarboxydus, was identified, cloned, and heterologously expressed in Escherichia coli. The purified recombinant StMCO exhibited the characteristic blue color and bivalent copper ion-dependent enzyme activity. It was capable of oxidizing the model substrate ABTS, phenolic compound DMP, and azo dye RB5. Notably, StMCO could directly degrade aflatoxin B1 (AFB1) and zearalenone (ZEN) in the absence of mediators. Meanwhile, the presence of various lignin unit-derived natural mediators or ABTS could significantly accelerate the degradation of AFB1 and ZEN by StMCO. Furthermore, the biological toxicities of their corresponding degradation products, AFQ1 and 13-OH-ZEN-quinone, were remarkably decreased. Our findings suggested that efficient degradation of mycotoxins with mediators might be a common feature of the MCOs superfamily. In summary, the unique properties of MCOs make them good candidates for degrading multiple major mycotoxins in contaminated feed and food.

Degradation of zearalenone and aflatoxin B1 by Lac2 from Pleurotus pulmonarius in the presence of mediators

The contamination of foods and feeds with mycotoxins has been an issue of global significance. For mycotoxin detoxification, enzymatic biodegradation using laccase has received much attention. In this study, a laccase gene lac2 from the fungus Pleurotus pulmonarius was expressed in the Pichia pastoris X33 yeast strain to produce recombinant proteins. Enzymatic properties of recombinant Lac2 and its ability to degrade zearalenone (ZEN) and Aflatoxin B1 (AFB1) in the presence of four mediators (ABTS, TEMPO, AS and SA) were investigated. Result showed that the optimum pH and temperature of recombinant Lac2 were 3.5 and 55 °C, respectively. Lac2 was not sensitive to heat and stable under both acidic and alkaline conditions. Lac2-ABTS and Lac2-AS were efficient systems for ZEN degradation over a wide range of pH (4-8) and temperature (40-60 °C). Lac2-AS was the most efficient system for AFB1 degradation, reaching 99.82% of degradation at pH 7 and 37 °C after 1 h of incubation. Finally, the Lac2-mediator oxidation products were structurally characterized. This study lays a solid foundation for the application of Lac2 laccase combined with AS for degrading mycotoxin in food and feed.