Survey On The Contamination Of Deoxynivalenol And Zearalenone And Screeing Of Mycotoxin-degradation Microbes In Grains

Mycotoxins are the secondary metabolites of fungi, resulting in the loss of nutrition and economic value of crops and damaging human health. Deoxynivalenol (DON) and zearalenone(ZEN), which are known as representative of mycotoxins produced by Fusarium, spread widely in crops and by-products all over the world. Traditionally physical and chemical treatment was used to remove DON and ZEN, however, several shortcomings such as incomplete degradation of toxin and loss of nutrients limited their broad application. Currently, transformation of mycotoxins into non-toxic products by metabolism of microorganism is a hot spot of research. Therefore, understanding the situation of mycotoxin contamination of foodstuffs, screening and isolating microbes for mycotoxin degradation are effective approach to realize the control of mycotoxins. The detailed information of this study was described as follows.In order to acquire a deep insight on DON and ZEN contamination level of foodstuffs in Anhui and Henan province, we conducted a survey on DON and ZEN content in foodstuffs from several counties of Anhui and Henan province in 2008. Enzyme linked immunosorbent assay (ELISA) and high performance liquid chromatography (HPLC) were applied for the detection of the content of DON and ZEN in maize and wheat. All the data were statistically analyzed by SPSS software.To screen out strains for degradation of mycotoxins, two strategies were chosen as follows:1. use mycotoxins as exclusive carbon source and microbes from contaminated maize, wheat, soil samples as candidates; 2. set up a model of DON contamination by feeding chickens and BALB/C mice with DON, therewith the microbial flora in intestine was used as a resource for screening of DON degradation strains under selective pressure. The results showed that none of DON removing microbes were isolated but 6 strains with the capacity of ZEN removing were found, the highest removing efficiency of one strains was as high as 75.5%.To obtain the classification of 6 isolates above,16S rDNA sequence PCR amplification and homologous searching and alignment were applied. The results showed they belonged to Brachybacterium rhamnosum, Ralstonia metallidurans. Enterococcus faecali, Bacillus cereus, Micrococcus luteus, and Burkholderia cepacia, respectively. Moreover, morphological observation, and physiological and biochemical reaction were also conducted to characterize the 6 strains.To optimize the culturing conditions of strains of Bacillus cereus and Micrococcus luteus for maximally removing off mycotoxins, several factors including temperature, culture time, medium, initial pH, rotation speed, carbon sources were approached. The optimized conditions were found as follows. For Bacillus cereus:BA broth, initial pH 6.5,180 rpm,37℃for 120 h. For Micrococcus luteus:LB borth, initial pH 7.0,180 rpm,37℃for 120 h. The maximal removing of ZEN achieved as high as 100% and 65.79%, respectively.