Detoxification of Deoxynivalenol by 60Co γ-ray Irradiation and Toxicity Analyses of Radiolysis Products.

Background: Deoxynivalenol (DON) is a type B trichothecene that occurs predominantly in grains such as wheat, maize, and barley and has been implicated in incidents of mycotoxicoses in both humans and farm animals. Objective: In the present study, we chose 60Co γ-ray irradiation to degrade DON. Methods: First, the degradation effect of irradiation on DON was analyzed. Second, the toxicity analyses of radiolysis products were studied by oral gavage. Results: The results indicated that 60Co γ-ray irradiation had significant degradation effect on pure DON: when 20 kGy γ-ray irradiation was used for 2 µg/mL DON in acetonitrile-water, the degradation efficiency of DON was 83%, and 2 µg/mL DON in ultra-pure water was completely degraded after 5 kGy γ-ray irradiation. The concentration of 200 µg/mL DON in ultra-pure water had significant toxicity to mice: decreased body weight gain and feed consumption as well as pathological changes in liver and kidney were observed compared with the control group. Conclusions: No significant toxicity was observed in mice that were given these degraded solutions treated by γ-ray irradiation, which indicated that the toxicity of radiolysis products in ultra-pure water had significantly decreased after treatment by γ-ray irradiation. Highlights: This research offered some reference to detoxify DON in cereal grains.

Effects of light on secondary metabolism and fungal development of Fusarium graminearum.

AIMS: The objectives of this study were (i) to characterize white-collar (WC) orthologues of the filamentous fungus Fusarium graminearum, (ii) to investigate light-responsive phenotypes by the deletion of Fgwc-1 and Fgwc-2 genes and (iii) to examine the roles of those genes in constant light and darkness in relation to secondary metabolite synthesis and development. METHODS AND RESULTS: Production of secondary metabolites and asexual/sexual development of deletion mutants, ΔFgwc-1 and ΔFgwc-2, were assessed in constant light and darkness compared to the wild-type strain. The results showed that deletion of Fgwc-1 and Fgwc-2 impaired early onset of carotenogenesis, photoreactivation and the maturity of perithecia during sexual development. Conidiation of the ΔFgwc-1 and ΔFgwc-2 mutants was derepressed in constant light, but not in darkness. Moreover, the individual mutants produced more aurofusarin and trichothecenes than the wild-type strain in both constant light and darkness. CONCLUSIONS: Both Fgwc-1 and Fgwc-2 are required for light-dependent processes in F. graminearum, whereas light-independent processes such as aurofusarin and trichothecene biosynthesis are derepressed by deletion of these genes. Thus, Fgwc-1 and Fgwc-2 play roles as positive and negative regulators, depending on the requirement of light for biological activity. SIGNIFICANCE AND IMPACT OF THE STUDY: These results will extend the knowledge of the photobiology of Fusarium graminearum and will increase current understanding of light regulatory mechanisms mediated by white collar in secondary metabolism and fungal development.

Application of the pulsed light technology to mycotoxin degradation and inactivation.

The persistence of mycotoxins and their metabolites in agricultural products is a major safety concern because of their high resistance to all kinds of decontamination techniques. In this study, we evaluated the effectiveness of the pulsed light technology for the degradation of mycotoxins. We report that eight flashes of pulsed light destroyed of 84.5 ± 1.9, 72.5 ± 1.1, 92.7 ± 0.8 and 98.1 ± 0.2% of zearalenone, deoxynivalenol, aflatoxin B1 and ochratoxin in solution. The degradation of the molecules was monitored by HPLC and LC-MS/MS analysis. We estimated the potential toxicity of zearalenone and deoxynivelenol after exposure to a pulsed light treatment using the Caenorhabditis elegans survival tests. The genotoxicity of aflatoxin B1 was also investigated using a complete Ames test. The results show that the treatment of zearalenone and deoxynivelenol by single or multiple flashes of pulsed light is associated with a stagnation or marginal decrease of the toxicity of the mycotoxins and that treatment of aflatoxin B1 by pulsed light can completely eliminate the mutagenic potential of this mycotoxin. This work provides the first demonstration of a nonthermal technology allowing mycotoxin destruction and inactivation of their mutagenic activity.

Reduction of deoxynivalenol contaminating corn silage by short-term ultraviolet irradiation: a pilot study.

We evaluated the effects of short-term (up to 60 min) irradiation of corn silage with ultraviolet (UV) light (intensity: 1.5 mW/cm(2) at 254 nm UV-C wavelength), along with constant stirring of the silage, on the concentration of deoxynivalenol (DON), a major feed-contaminating mycotoxin, and those of α-tocopherol (vitamin E) and ß-carotene (pro-vitamin A). The initial DON concentration in artificially contaminated silage was set at approximately 60 µg/g dry silage weight. After irradiation, the level of DON was decreased significantly (P<0.05) by approximately 13 µg/g (22%) on average at 30 min, and by 12 µg/g (21%) at 60 min. However, the concentrations of the vitamins remained relatively unaffected. Although further improvement is needed, short-term UV irradiation seems a promising on-farm method for reducing the level of DON in feedstuffs.

Reduction of feed-contaminating mycotoxins by ultraviolet irradiation: an in vitro study.

Ultraviolet (UV) germicidal irradiation has been applied to the sterilization of agricultural products including stored grain for foodstuffs or animal feed. Although UV treatment is known to be effective for killing pathogenic moulds that contaminate the surface of grain, it remains unclear how and to what extent such irradiation is able to eliminate mycotoxins, the fungal metabolites that have adverse effects on human and animal health. We evaluated in vitro the effects of mild (intensity = 0.1 mW cm(-2) at 254 nm UV-C) and strong (24 mW cm(-2)) UV irradiation on two feed-contaminating mycotoxins, zearalenone (ZEN) and deoxynivalenol (DON). When exposed to mild irradiation, the levels of ZEN and DON (both 30 mg kg(-1) initially) were reduced as irradiation time increased, and became undetectable at 60 min. Strong UV irradiation also reduced the mycotoxin levels in the same time-dependent manner, but more rapidly. It was therefore confirmed in vitro that UV irradiation is effective at reducing the levels of ZEN and DON. The present study provides preliminary data for establishing a practical method of using UV irradiation to reduce mycotoxin contamination in grain intended for use in feed.

The stability of deoxynivalenol and 3-acetyl deoxynivalenol to gamma irradiation.

The stability of deoxynivalenol and 3-acetyl deoxynivalenol to irradiation by 60Co-gamma radiation under various conditions was investigated. Deoxynivalenol and 3-acetyl deoxynivalenol were irradiated on maize, in aqueous solution and in the dry state. Breakdown of the toxins was monitored by high performance liquid chromatography. Both deoxynivalenol and 3-acetyl deoxynivalenol were more sensitive to irradiation when irradiated in aqueous solution than when irradiated on maize. Breakdown of deoxynivalenol and 3-acetyl deoxynivalenol in aqueous solution began at 1 kGy and 5 kGy respectively and both toxins were completely destroyed by 50 kGy. When irradiated on maize, breakdown of the toxins only began after irradiation to 20 kGy and 80-90% of the toxins remained after irradiation to 50 kGy. Irradiation of the toxins did not cause the formation of new compounds of increased toxicity to baby hamster kidney cells. Both DON and 3-A DON were stable to irradiation to 50 kGy when irradiated in the dry condition. The use of low dose gamma irradiation to destroy preformed toxins present on grain does not appear to be a suitable method for the detoxification of grain contaminated with deoxynivalenol and 3-acetyl deoxynivalenol because of the high irradiation dose that would be required for their destruction (> 50 kGy).