Zearalenone enzimatic degradation: food safety and quality perspectives

Zearalenone (ZEN) is a non-steroideal estrogenic mycotoxin produced by Fusarium spp, such as F. culmorum, F. graminearum, F. cerealis, and F. equiseti., and one of the most occurring mycotoxin in cereal-based products. Due to its structural similarity with 17-?-estradiol, its ingestion induces hormonal dysregulations, infertility, embryo toxicity, apoptosis, and oxidative stress in both humans and animals. Since mycotoxin prevention is difficult to obtain, their post-harvest reduction is necessary to ensure that safe food and feed are produced. Hence, different methods have been studied to reduce ZEN contamination in feed. Among them, the enzymatic remediation has proven to be an effective, yet mild approach, especially if green enzymes, like laccases (LCs), are used. Indeed LCs are versatile multicopper oxidases which require molecular oxygen as electron acceptor and produce to water as by-product. Therefore, in this work ZEN degradation was assessed in vitro using Ery4 laccase (5 U/mL) and four different mediators (10mM), two natural occurring phenols, i.e. acetosyringone (AS) and syringaldehyde (SA), and two synthetic compounds, 2-azino-di-[3-ethylbenzo-thiazolin-sulphonate] (ABTS) and 2,2,6,6-tetramethylpyperidyloxil (TEMPO). The best performing mediator was then used for ZEN degradation in naturally contaminated corn flour (146 ± 12.8 ?g/kg). As requested by European regulation n. 786/2015 defining acceptability criteria on detoxification process, to assess whether the process adversely affected the characteristics and the nature of the matrix, a preliminary evaluation of the corn flour after the enzymatic treatment was performed. In particular, protein content and quality, as well as the oxidative status were investigated. ZEN was completely removed in vitro with all mediators tested after 72h of incubation at 25°C. Therefore, for a deeper investigation, a time course evaluation was performed using the natural compounds AS and SA. AS was the best performing mediator, as it enable to completely remove ZEN after only 30min. AS was then used together with Ery4 for ZEN reduction in corn flour, obtaining a reduction of 43.7 ± 8.5%. The protein content and the electrophoretic pattern of corn were not altered by the enzymatic treatment. On the contrary, a slight increase in lipid peroxidation and H2O2 content was observed, though still at physiological levels. The results of this work show that Ery4 and AS are efficient tools to reduce ZEN contamination in vitro and in a naturally contaminated matrix. A slight oxidation could be observed in the treated samples, nonetheless, the protein quantity and quality were not altered. Even though further studies are needed to comprehensively evaluate the effect of the enzymatic treatment on the nutritional and technological properties of corn flour, this study suggests that the enzymatic treatment minimally impacts the characteristic of the matrix and could be used to dramatically improve the safety of cereal-based products