Application of luminescent Photobacterium Phosphoreum T3 for the detection of zearalenone and estimating the efficiency of their enzymatic degradation

Zearalenone (ZEN), a nonsteroidal estrogenic mycotoxin, causes enormous economic losses in the food and feed industries. Simple, rapid, low-cost, and quantitative analysis of ZEN is particularly urgent in the fields of food safety and animal husbandry. Using the bioluminescent bacterium Photobacterium phosphoreum T3, we propose a bioluminescence inhibition assay to evaluate ZEN levels quickly. The limit of detection (LOD), limit of quantification (LOQ), and quantitative working range of this bioluminescence inhibition assay were 0.1 µg/mL, 5 µg/mL, and 5-100 µg/mL, respectively. The concentration-response curve of the bioluminescence inhibition rate and ZEN concentration was plotted within the range 5 to 100 μg/mL, as follows: y = 0.0069x2 - 0.0190x + 7.9907 (R2 = 0.9943, y is luminescence inhibition rate, x is ZEN concentration). First, we used the bioluminescence inhibition assay to detect the remaining ZEN in samples treated with purified lactonohydrolase ZHD101. The bioluminescence inhibition assay results showed a strong correlation with the HPLC analysis. Furthermore, we successfully evaluated the overall toxicity of samples treated with purified peroxidase Prx and H2O2 using the P. phosphoreum T3 bioluminescence inhibition assay. The results indicate that the degradation products of ZEN created by purified peroxidase Prx and H2O2 showed little toxicity to P. phosphoreum T3. In this study, a simple, rapid, and low-cost assay method of zearalenone by bioluminescent P. phosphoreum T3 was developed. The bioluminescence inhibition assay could be used to estimate the efficiency of enzymatic degradation of ZEN.

Recombinant expression and surface display of a zearalenone lactonohydrolase from Trichoderma aggressivum in Escherichia coli

Zearalenone (ZEN), one of the most dangerous mycotoxins, causes enormous economic losses in the food and feed industries. To solve the problem of ZEN pollution, ZEN detoxifying enzymes are in emergent need. In this study, a zearalenone lactonohydrolase from Trichoderma aggressivum, denoted as ZHD-P, was heterologously expressed and characterized. The intracellular ZHD-P from E. coli BL21(DE3) exhibited high activity for ZEN degradation (191.94 U/mg), with the optimal temperature and pH of 45 °C and 7.5-9.0, respectively. With excellent temperature stability, the intracellular ZHD-P retained 100% activity when it was incubated at 25-40 °C for 1 h. Furthermore, we firstly constructed an E. coli cell surface display system for ZHD-P. The surface-displayed ZHD-P exhibited high activity against ZEN and showed optimal activity at 40 °C and pH 9.0. With superior pH stability, the surface-displayed ZHD-P retained 80% activity when it was incubated at pH 5.0-11.0 for 12 h. Interestingly, the metal ions tolerance of the surface-displayed ZHD-P was better than the intracellular form. Additionally, the surface-displayed ZHD-P could be reused four times with the residual enzyme activity of more than 50%. The biotoxicity assessment using P. phosphoreum T3 indicated that ZEN could be degraded into hypotoxic products by the intracellular or surface-displayed ZHD-P. ZHD-P could be feasible for ZEN detoxification.

Critical evaluation of LC-MS-based methods for simultaneous determination of deoxynivalenol, ochratoxin A, zearalenone, aflatoxins, fumonisins and T-2/HT-2 toxins in maize

The results of a proficiency test for the LC-MS/(MS) determination of up to 11 mycotoxins (aflatoxins B1, B2, G1 and G2, fumonisins B1 and B2, ochratoxin A, deoxynivalenol, T-2 and HT-2 toxins and zearalenone) in maize were evaluated to identify possible strengths and weaknesses of various methodologies used by the 41 participating laboratories. The majority of laboratories (56%) used mixtures of acetonitrile:water for extraction. Other laboratories used methanol:water mixtures (17%) or performed two consecutive extractions with phosphate buffer solution (PBS) followed by methanol (15%). Few laboratories used mixtures of acetonitrile:water:methanol (7%), water:ethyl acetate (2.5%) or PBS alone (2.5%). The majority of laboratories (58%) used a clean-up step prior to chromatography. The remaining laboratories analysed crude extracts (37%) or used a mixed approach (5%). The amount of sample equivalent injected into LC-MS/(MS) ranged between 0.1-303 mg for purified extracts and 0.08-20 mg for directly analysed crude extracts. External (54%), matrix-matched (22%) or stable isotope-labelled internal standards calibration (24%) were used for toxin quantification. In general, extraction mixtures of water with acetonitrile, methanol or both provided good results for quantitative extraction of mycotoxins from maize. Laboratories using sample extract clean-up reported acceptable results for the majority of mycotoxins. Good results were also obtained by laboratories that analysed crude extracts although a high variability of results was observed for all tested mycotoxins. Matrix-matched calibration or isotope-labelled internal standards efficiently compensated matrix effects whereas external calibration gave reliable results by injecting ≤10 mg of matrix equivalent amounts. Unacceptable high recovery and high variability of fumonisin results were obtained by the majority of laboratories, which could not be explained and thus require further investigation. These findings provide the basis for the optimization and selection of methods to be used in future interlaboratory validation studies to derive their performance characteristics for simultaneous determination of mycotoxins in maize.

A design of experiments approach to studying deoxynivalenol and deoxynivalenol-3-glucoside evolution throughout industrial production of wholegrain crackers exploiting LC-MS/MS techniques

Fusarium mycotoxins represent a significant problem in the cereal supply chain, with wheat, maize and barley being the main contaminated crops. Among the Fusarium toxins, the trichothecene deoxynivalenol (DON) is considered to be the most important contaminant in wheat due to its widespread occurrence. To protect consumers from unacceptably high trichothecene intakes in their diets, many countries have set maximum trichothecene levels for cereals and related food commodities. Relatively few studies have considered the loss of trichothecenes during industrial processing and focused on how processing steps may influence their degradation or modification. The aim of the present study is to verify how the DON and deoxynivalenol-3-glucoside (DON-3G) concentration in wholegrain crackers can be influenced by changes to the technological parameters employed during the fermentation and baking steps, starting with naturally contaminated bran, using a pilot-scale plant and exploiting the power of the Design of Experiments (DoE) approach. The DON results were then used to generate a preliminary predictive model, suggesting that the baking step represents the most important phase in minimising the native toxin level in crackers.

Developments in mycotoxin analysis: an update for 2008-2009

This review highlights developments in mycotoxin analysis and sampling over a period between mid-2008 and mid-2009. It covers the major mycotoxins: aflatoxins, alternaria toxins, cyclopiazonic acid, fumonisins, ochratoxin, patulin, trichothecenes and zearalenone. Developments in mycotoxin analysis continue, with emphasis on novel immunological methods and further description of LC-MS and LC-MS/MS, particularly as multimycotoxin applications for different ranges of mycotoxins. Although falling outside the main emphasis of the review, some aspects of natural occurrence have been mentioned, especially if linked to novel method developments.