Abstract
The co-occurrence of multiple mycotoxins, including aflatoxin B1 (AFB1), zearalenone (ZEN) and deoxynivalenol (DON), widely exists in cereal-based animal feed and food. At present, most reported mycotoxins degrading enzymes target only a certain type of mycotoxins. Therefore, it is of great significance for mining enzymes involved in the simultaneous degradation of different types of mycotoxins. In this study, a dye-decolorizing peroxidase-encoding gene BsDyP from Bacillus subtilis SCK6 was cloned and expressed in Escherichia coli BL21/pG-Tf2. The purified recombinant BsDyP was capable of oxidizing various substrates, including lignin phenolic model compounds 2,6-dimethylphenol and guaiacol, the substrate 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid), anthraquinone dye reactive blue 19 and azo dye reactive black 5, as well as Mn2+. In addition, BsDyP could efficiently degrade different types of mycotoxins, including AFB1, ZEN and DON, in presence of Mn2+. More important, the toxicities of their corresponding enzymatic degradation products AFB1-diol, 15-OH-ZEN and C15H18O8 were significantly lower than AFB1, ZEN and DON. In summary, these results proved that BsDyP was a promising candidate for the simultaneous degradation of multiple mycotoxins in animal feed and food.
Highlights
Mycotoxins are a diverse group of toxic secondary metabolites produced by certain filamentous fungi, and they display carcinogenicity, teratogenicity, immune toxicity, neurotoxicity, hepatotoxicity, nephrotoxicity, reproductive and developmental toxicity towards humans and animals [1]
As for biotransformation of multiple mycotoxins, several microorganisms such as Bacillus subtilis, Rhodococcus percolatus and Pseudomonas putida have been reported to be capable of degrading aflatoxins B1 (AFB1) and ZEN [7,10,11,12]
Bacterial and fungal laccases could simultaneously degrade AFB1 and ZEN, using the laccase/mediator systems [14]. Another ligninolytic enzyme dye-decolorizing peroxidase (DyP) from B. subtilis SCK6 was expressed in Escherichia coli, using the cold shock-inducible expression system coupled with co-expression of chaperones
Summary
Mycotoxins are a diverse group of toxic secondary metabolites produced by certain filamentous fungi, and they display carcinogenicity, teratogenicity, immune toxicity, neurotoxicity, hepatotoxicity, nephrotoxicity, reproductive and developmental toxicity towards humans and animals [1]. More than 400 mycotoxins have been identified and reported; only a few mycotoxins dominate in contaminated food and animal feed. These are aflatoxins B1 (AFB1 ), zearalenone (ZEN), deoxynivalenol (DON), ochratoxin A, fumonisin B1, citrinin and patulin [2,3]. The detoxification of mycotoxins through biotransformation by microorganisms or their enzymes has gradually become one of the most promising strategies because of its advantages in efficiency, specificity and environmental friendliness [7,9]. As for biotransformation of multiple mycotoxins, several microorganisms such as Bacillus subtilis, Rhodococcus percolatus and Pseudomonas putida have been reported to be capable of degrading AFB1 and ZEN [7,10,11,12]. Only a few enzymes have been identified, purified and characterized for multiple mycotoxin biotransformation
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