Effective Zearalenone Degradation in Model Solutions and Infected Wheat Grain Using a Novel Heterologous Lactonohydrolase Secreted by Recombinant Penicillium canescens

The Protein Engineering of Zearalenone Hydrolase Results in a Shift in the pH Optimum of the Relative Activity of the Enzyme

An acidic shift in the pH profile of Clonostachys rosea zearalenone hydrolase (ZHD), the most effective and well-studied zearalenone-specific lactone hydrolase, is required to extend the range of applications for the enzyme as a decontamination agent in the feed and food production industries. Amino acid substitutions were engineered in the active center of the enzyme to decrease the pKa values of the catalytic residues E126 and H242. The T216K substitution provided a shift in the pH optimum by one unit to the acidic region, accompanied by a notable expansion in the pH profile under acidic conditions. The engineered enzyme demonstrated enhanced activity within the pH range of 3-5 and improved the activity within the pH ranging from 6 to 10. The D31N and D31A substitutions also resulted in a two-unit shift in the pH optimum towards acidic conditions, although this was accompanied by a significant reduction in the enzyme activity. The D31S substitution resulted in a shift in the pH profile towards the alkaline region. The alterations in the enzyme properties observed following the T216K substitution were consistent with the conditions required for the ZHD application as decontamination enzymes at acidic pH values (from 3.0 to 6.0).

Mycotoxin Biodegradation by Bacillus Bacteria-A Review

Mycotoxins are toxic secondary metabolites produced by various types of fungi that are known to contaminate various food products; their presence in the food chain poses significant risks to human and animal health and leads to enormous economic losses in the food and feed industry worldwide. Ensuring food safety and quality by detoxifying mycotoxin is therefore of paramount importance. Several procedures to control fungal toxins have been extensively investigated, such as preventive measures, physical and chemical methods, and biological strategies. In recent years, microbial degradation of mycotoxins has attracted much attention due to its reliability, efficiency, and cost-effectiveness. Notably, bacterial species from the Bacillus genus have emerged as promising candidates for mycotoxin decontamination owing to their diverse metabolic capabilities and resilience in harsh environmental conditions. This review manuscript aims to provide a summary of recent studies on the biodegradation of fungal toxins by Bacillus bacteria, thereby illustrating their potential applications in the development of mycotoxin-degrading products.

The occurrence and biological control of zearalenone in cereals and cereal-based feedstuffs: a review

Zearalenone, a prominent mycotoxin produced by Fusarium spp., ubiquitously contaminates cereal grains and animal feedstuffs. The thermal stability of zearalenone creates serious obstacles for traditional removal methods, which may introduce new safety issues, or reducing nutritional quality. In contrast, biological technologies provide appealing benefits such as easy to apply and effective, with low toxicity byproducts. Thus, this review aims to describe the occurrence of zearalenone in cereals and cereal-based feedstuffs in the recent 5 years, outline the rules and regulations regarding zearalenone in the major countries, and discuss the recent developments of biological methods for controlling zearalenone in cereals and cereal-based feedstuffs. In addition, this article also reviews the application and the development trend of biological strategies for removal zearalenone in cereals and cereal-based feedstuffs.

Bioenzymatic detoxification of mycotoxins

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.

A new physical and biological strategy to reduce the content of zearalenone in infected wheat kernels: the effect of cold needle perforation, microorganisms, and purified enzyme

With the aim of reintroducing wheat grains naturally contaminated with mycotoxins into the food value chain, a decontamination strategy was developed in this study. For this purpose, in a first step, the whole wheat kernels were pre-treated using cold needle perforation. The pore size was evaluated by scanning electron microscopy and the accessibility of enzymes and microorganisms determined using fluorescent markers in the size range of enzymes (5 nm) and microorganisms (10 μm), and fluorescent microscopy. The perforated wheat grains, as well as non-perforated grains as controls, were then incubated with selected microorganisms (Bacillus megaterium Myk145 and B. licheniformis MA572) or with the enzyme ZHD518. The two bacilli strains were not able to significantly reduce the amount of zearalenone (ZEA), neither in the perforated nor in the non-perforated wheat kernels in comparison with the controls. In contrast, the enzyme ZHD518 significantly reduced the initial concentration of ZEA in the perforated and non-perforated wheat kernels in comparison with controls. Moreover, in vitro incubation of ZHD518 with ZEA showed the presence of two non-estrogenic degradation products of ZEA: hydrolysed zearalenone (HZEA) and decarboxylated hydrolysed ZEA (DHZEA). In addition, the physical pre-treatment led to a reduction in detectable mycotoxin contents in a subset of samples. Overall, this study emphasizes the promising potential of combining physical pre-treatment approaches with biological decontamination solutions in order to address the associated problem of mycotoxin contamination and food waste reduction.

Mechanisms by which microbial enzymes degrade four mycotoxins and application in animal production: A review

Mycotoxins are toxic compounds that pose a serious threat to animal health and food safety. Therefore, there is an urgent need for safe and efficient methods of detoxifying mycotoxins. As biotechnology has continued to develop, methods involving biological enzymes have shown great promise. Biological enzymatic methods, which can fundamentally destroy the structures of mycotoxins and produce degradation products whose toxicity is greatly reduced, are generally more specific, efficient, and environmentally friendly. Mycotoxin-degrading enzymes can thus facilitate the safe and effective detoxification of mycotoxins which gives them a huge advantage over other methods. This article summarizes the newly discovered degrading enzymes that can degrade four common mycotoxins (aflatoxins, zearalenone, deoxynivalenol, and ochratoxin A) in the past five years, and reveals the degradation mechanism of degrading enzymes on four mycotoxins, as well as their positive effects on animal production. This review will provide a theoretical basis for the safe treatment of mycotoxins by using biological enzyme technology.

Recombinant Oxidase from Armillaria tabescens as a Potential Tool for Aflatoxin B1 Degradation in Contaminated Cereal Grain

Forage grain contamination with aflatoxin B1 (AFB1) is a global problem, so its detoxification with the aim of providing feed safety and cost-efficiency is still a relevant issue. AFB1 degradation by microbial enzymes is considered to be a promising detoxification approach. In this study, we modified an previously developed Pichia pastoris GS115 expression system using a chimeric signal peptide to obtain a new recombinant producer of extracellular AFB1 oxidase (AFO) from Armillaria tabescens (the yield of 0.3 g/L), purified AFO, and selected optimal conditions for AFO-induced AFB1 removal from model solutions. After a 72 h exposure of the AFB1 solution to AFO at pH 6.0 and 30 °C, 80% of the AFB1 was degraded. Treatments with AFO also significantly reduced the AFB1 content in wheat and corn grain inoculated with Aspergillus flavus. In grain samples contaminated with several dozen micrograms of AFB1 per kg, a 48 h exposure to AFO resulted in at least double the reduction in grain contamination compared to the control, while the same treatment of more significantly (~mg/kg) AFB1-polluted samples reduced their contamination by ~40%. These findings prove the potential of the tested AFO for cereal grain decontamination and suggest that additional studies to stabilize AFO and improve its AFB1-degrading efficacy are required.

Characterization of modified rice straw biochar in immobilizing Bacillus subtilis 168 and evaluation on its role as a novel agent for zearalenone-removal delivery

Microbial remediation of environmental pollutants can be advanced by carrier based cells immobilization. Whereas the effects of microorganisms immobilized on biochar for removal of zearalenone (ZEN) still remain unknown. Herein, this work presented the characterization of rice straw biochar (RSB) around modification in immobilizing Bacillus subtilis 168 and the role in fighting ZEN in vitro. Specifically, 10% of RSB with pH 5 condition were optimal for bearing cells, where majority of cells loaded inside the pore and minority on surface with agglomeration or scattering status. Octadecyl trimethyl ammonium chloride-inclusion RSB showed better performances including over 93% of ZEN detoxification rate (32.48% in free cells), cells preservation, and stability of detoxification in simulated gastrointestinal environment. RSB treated with sulphuric acid made nutrients adsorption generally less than 6.5%. No residues of α-ZEL and α-ZAL were found in ZEN biotransformation process whether by free cells or composites. Mechanism discussion implied that predominant monolayer chemisorption by RSB and subsequent biodegradation by extracellular enzymes from microorganism involved in ZEN-removal process. Collectively, these findings contribute to provide an applying strategy for coordination of biochar and microorganisms as potentially mycotoxin detoxifying agent in agricultural feed bioremediation and environmental decontamination processes.

Post-Harvest Prevention of Fusariotoxin Contamination of Agricultural Products by Irreversible Microbial Biotransformation: Current Status and Prospects

Biological degradation of mycotoxins is a promising environmentally-friendly alternative to chemical and physical detoxification methods. To date, a lot of microorganisms able to degrade them have been described; however, the number of studies determining degradation mechanisms and irreversibility of transformation, identifying resulting metabolites, and evaluating in vivo efficiency and safety of such biodegradation is significantly lower. At the same time, these data are crucial for the evaluation of the potential of the practical application of such microorganisms as mycotoxin-decontaminating agents or sources of mycotoxin-degrading enzymes. To date, there are no published reviews, which would be focused only on mycotoxin-degrading microorganisms with the proved irreversible transformation of these compounds into less toxic compounds. In this review, the existing information about microorganisms able to efficiently transform the three most common fusariotoxins (zearalenone, deoxinyvalenol, and fumonisin B1) is presented with allowance for the data on the corresponding irreversible transformation pathways, produced metabolites, and/or toxicity reduction. The recent data on the enzymes responsible for the irreversible transformation of these fusariotoxins are also presented, and the promising future trends in the studies in this area are discussed.

Enzymatic Degradation of Zearalenone in the Gastrointestinal Tract of Pigs, Chickens, and Rainbow Trout

The estrogenic mycotoxin zearalenone (ZEN) is a common contaminant of animal feed. Effective strategies for the inactivation of ZEN in feed are required. The ZEN-degrading enzyme zearalenone hydrolase ZenA (EC 3.1.1.-, commercial name ZENzyme^®, BIOMIN Holding GmbH, Getzersdorf, Austria) converts ZEN to hydrolyzed ZEN (HZEN), thereby enabling a strong reduction in estrogenicity. In this study, we investigated the efficacy of ZenA added to feed to degrade ZEN in the gastrointestinal tract of three monogastric animal species, i.e., pigs, chickens, and rainbow trout. For each species, groups of animals received (i) feed contaminated with ZEN (chickens: 400 µg/kg, pigs: 200 µg/kg, rainbow trout: 2000 µg/kg), (ii) feed contaminated with ZEN and supplemented with ZenA, or (iii) uncontaminated feed. To investigate the fate of dietary ZEN in the gastrointestinal tract in the presence and absence of ZenA, concentrations of ZEN and ZEN metabolites were analyzed in digesta of chickens and rainbow trout and in feces of pigs. Upon ZenA administration, concentrations of ZEN were significantly decreased and concentrations of the degradation product HZEN were significantly increased in digesta/feces of each investigated animal species, indicating degradation of ZEN by ZenA in the gastrointestinal tract. Moreover, upon addition of ZenA to the diet, the concentration of the highly estrogenic ZEN metabolite α-ZEL was significantly reduced in feces of pigs. In conclusion, ZenA was effective in degrading ZEN to HZEN in the gastrointestinal tract of chickens, pigs, and rainbow trout, and counteracted formation of α-ZEL in pigs. Therefore, ZenA could find application as a ZEN-degrading feed additive for these animal species.

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.

Network pharmacology-based study on the mechanism of scutellarin against zearalenone-induced ovarian granulosa cell injury

Zearalenone(ZEA) is a kind of mycotoxin widely existing in nature, its toxic effects can lead to the reproductive disorders in humans and animals. The aim of this study was to investigate the mechanism of scutellarin against ovarian granulosa cell(GCs) injury induced by ZEA based on network pharmacology, molecular docking method. The results show that 293 drug targets of scutellarin were found from PhamMapper database, and 583 disease targets were selected from Genecards database. Finally, 57 scutellarin targets were obtained for the repair of GCs injury with gene intersection. The protein-protein interaction(PPI), gene ontology(GO) and kyoto encyclopedia of genes and genomes(KEGG) analysis indicated that MAPK signaling pathway was most likely activated by scutellarin. Scutellarin with JNK or Caspase-3 had minimal and negative free binding energy in molecular docking analysis, indicating that they might be the acting targets of scutellarin. Cell viability was significantly decreased in ZEA treated cells. However, GCs viability, the level of estradiol(E₂) and progesterone(P₄) were significantly increased with addition of scutellarin to ZEA treated cells. Western blot analysis showed that scutellarin significantly reduced the expression of JNK, c-jun and Cleaved-caspasee-3 in GCs compared with ZEA treatment. In conclusion, scutellarin could alleviate the ovarian GCs injury by down-regulating the expression of JNK, c-jun and Cleaved-caspase-3 through the activation of MAPK/JNK signaling pathway. Our results will provide a theoretical foundation for the treatment of reproductive disorders with scutellarin.

Using Cholinesterases and Immobilized Luminescent Photobacteria for the Express-Analysis of Mycotoxins and Estimating the Efficiency of Their Enzymatic Hydrolysis

Novel sensitive analytical agents that can be used for simple, affordable, and rapid analysis of mycotoxins are urgently needed in scientific practice, especially for the screening of perspective bio-destructors of the toxic contaminants. We compared the characteristics of a rapid quantitative analysis of different mycotoxins (deoxynivalenol, ochratoxin A, patulin, sterigmatocystin, and zearalenone) using acetyl-, butyrylcholinesterases and photobacterial strains of luminescent cells in the current study. The best bioindicators in terms of sensitivity and working range (μg/mL) were determined as follows: Photobacterium sp. 17 cells for analysis of deoxynivalenol (0.8-89) and patulin (0.2-32); Photobacterium sp. 9.2 cells for analysis of ochratoxin A (0.4-72) and zearalenone (0.2-32); acetylcholinesterase for analysis of sterigmatocystin (0.12-219). The cells were found to be more sensitive than enzymes. The assayed strains of photobacterial cells ensured 44%-83% lower limit of detection for deoxynivalenol and sterigmatocystin as compared to the previously known data for immobilized luminescent cells, and the range of working concentrations was extended by a factor of 1.5-3.5. Calibration curves for the quantitative determination of patulin using immobilized photobacteria were presented in this work for the first time. This calibration was applied to estimate the enzyme efficiency for hydrolyzing mycotoxins using zearalenone and His6-tagged organophosphorus hydrolase as examples.