The Selection Of High-Yield Siderophpres Producing Strains And Separation And Purification Of The Siderophores

Iron is an essential element of the living organisms, it plays an important role in the metabolic processes of the organisms. In microbial metabolic processes, the iron is the cofactor or activator of many enzymes, such as cytochrome, cytochrome oxidase, catalase, ferredoxin protein, iron sulfur protease and so on. On the condition that organisms are lack of iron, the metabolic processes above will be impacted significantly.Siderophore is a low molecular weight (500-1000Da) organic compound that microorganism produces in low iron stress conditions, and can combine with Fe3+efficiently. Its biosynthesis is strictly controlled by the concentration of iron.In this study,326strains bacteria were isolated from the intestine and gills of marine fishes from the offshore area of Qingdao by using LB medium and2216E medium.52high-yield siderophore-producing strains were selected by employing CAS solid and liquid methods, their productivity are all above50%.30of the52high-yield siderophore-producing strains can produce hydroxamate siderophores,16of those can produce catechol siderophores and8of those can produce both of them by iron perchlorate tests, iron chloride tests, csaky tests and arown tests. The results show that the strain CB-EH-2is the predominant strain of producing siderophores. Siderophores production was83.116%and reached6.299mg/L.Strain CB-EH-2was identificed as Cobetia marina using16S rDNA-based method. Different concentrations of Fe2+and2,2’-bipyridine were respectively added into the medium for exploring their effect on siderophore production. The result shows that when the2,2’-bipyridine concentration reachs50μmol/L, the siderophore production is highest; when concentration of2,2’-bipyridine exceeds200μmol/L, the strain doesn’t grow. The results shows that trace amounts of2,2’-bipyridine can stimulate CB-EH-2to produce siderophores. When the Fe2+concentration is more than10μmol/L, the strain was in the iron-rich environment and the synthesis of siderophore was inhibited. In the iron-rich condition, the increase in the concentration of Fe3+has little effect on the cell yield.The siderophores from CB-EH-2were purified using macroporous resin XAD-2and Sephadex HL-20. The partial purified compounds could inhabit the growth of Staphylococcus aureus, Escherichia coli, Vibrio brilliant4501and Vibrio anguillarum VB1. While emplying high performance liquid chromatography and electrospray ionization electric ion mass spectrometry (LC-MS) to identify the partial purified product, two compounds were got, one is a kind of siderophore, and another is identified as lipopeptide.