Isolation,Identification And Degradation Characteristic Of A Zearalenone-degrading Bacteria

Zearalenone(ZEN)is a class of 2,4-dihydroxybenzoide compounds produced by Fusarium such as F.graminearum and F.tricinctum.ZEN has the effect of estrogen,which can cause the reproductive system disorder of animals,liver and kidney damage,interfere with the immune system and be carcinogenic,harmful to animal and human seriously and can cause huge economic losses in animal husbandry every year.The purpose of this study is to quickly and effectively reduce ZEN in the feed by biodegradation.The following work is carried out:(1)A total of 70 samples of cow manure,sheep manure and soil were collected from different areas and 164 strains were isolated to screen the ZEN degradation strain.Using cyclopentanone as the sole carbon source of the primary screening medium,in order to isolate bacteria from 164 strains,and ZEN as the sole carbon source of the secondary screening medium was used for the secondary screening of the primary screening strains,and obtain 8strains of ZEN degradation strain.The ZEN degradation efficiency of 8 strains obtained after two screening was determined by high performance liquid chromatography(HPLC),and one strain with high ZEN degradation rate was detected,that is,NF-PJ-5 strain.The 16S rDNA sequence comparison,phylogenetic tree construction,colony morphology observation and physiological and biochemical identification experiments were conducted on the strain,and it was finally determined as a Sphingobacterium multivorum.(2)ZEN degradation property of this strain was evaluated from three factors:temperature,pH and concentration of bacterial solution.The results showed that when the concentration of bacterial solution was above 2×10~9 CFU/mL,28~32?and pH was 6.5~7.5,the bacterial strain maintained a relatively high degradation rate for ZEN whose initial concentration was 10?g/mL.Moreover,under the culture condition of 30?,pH of 7.0,and the shaking table rotating speed of 160 rpm/min,the degradation rate of the strain against the zearalenone with the initial concentration of 10?g/mL was around 83%after 48 h of culture.(3)The degradation mechanism of this strain to ZEN was preliminarily explored,and the results showed that the supernatant of this strain had a strong ability to degrade ZEN,and the degradation rate could reach more than 75%.At the same time,during the study on ZEN adsorption of the strain,it was found that the cell wall of the strain had a certain adsorption effect on ZEN and could adsorb about 20%of ZEN.It was speculated that this strain could completely degrade and remove ZEN in the environment by producing an extracellular enzyme capable of degrading ZEN and the adsorption of cell wall.In this study,the characteristics of Sphingobacterium multivorum in the degradation of ZEN were found for the first time,which further enriched the types of ZEN degradation strains and provided some technical and theoretical guidance for the application of biodegradation method.