| Siderophores, the low-molecular-weight iron(Ⅲ) chelators secreted by microorganisms, their main biological function is helping microorganisms to gain this limited key nutrient element through chelating iron specifically. It is an important strategy for microorganism against iron limited environment widespread in nature. Because the physiological role of siderophores in microorganism is to solubilize iron(Ⅲ) and shuttle it back to cytoplasm, so they have the potential to become iron nutrition enhancer, some reports in plant nutrition field also can support that. Siderophores from Synechococcus sp. PCC 7002 or named Synechobactins belong to the marine siderophores, they are a series of siderophores with varies length hydrophobic tails but the same hydrophilic head. This paper studies the siderophores production through fermentation from a cyanobacteria synechococcus sp.PCC 7002, on the basis of siderophore producted and prepared the iron absorption mechanism in Caco-2 cell intestinal model and anemia intervention in anemia rats model of iron chelate of siderophore crude product (SFE-Fe and SCE-Fe) were sdudied. The results of works are shown as follows:1. Optimization of siderophores fermentation conditions from synechococcus sp.PCC 7002 cultivated in photobioreactor.An enclosed bubble column photobioreactor was designed for Synechococcus sp.PCC 7002 cultivated in iron limited condition, and the influences of five factors including light intensity, temperature, CO2 concentration, aeration rate and inoculating ratio on siderophores fermentation in iron limited condition are studied and the optimized fermentation conditions were as follows:light intensity is 140 μmol/(m2·s) , temperature is 30"C, the concentration of CO2 is 0.5%, the aeration rate is 1.5 L/min and the inoculating population ratio is 125. The siderophores can be harvested after 3 days since inoculated and the siderophore unit can be 92.35±1.36%. The problem of growth limitation of synechococcussp.PCC 7002 and low siderophore production in iron limited condition has been solved basicaly.2. The intestinal absorption mechanism of SFE-Fe through Caco-2 cell intestinal model.Caco-2 cells were cultivated in 24-holes cell culture plated with collagen covered, in-vitro intestinal cells model was obtained after 12 days growth. The iron absorption condition can be reflected by the calcein fluoresce intensity changing of cell labile iron pool which is marked. The absorption pattern can be verified when Baphenanthrolinedisulfonic acid disodium salt is added to intervene the ferrous iron absorption through DMT1 pathway. The results indicate that when ferric iron chelated with SFE can be strongly absorbed in partial-acid intestinal environment.Both two pathways of whole-molecular and DMT1 path-way after reduction by Dcytb work when absorption, the main one is whole-molecular. The ferric iron chelated with SFE has higher reducibility in intestinal environment than other chelates because of the special ferric citrate complex work. In addition, the absorption of the ferric complex can be intervened less by sodium phytate, and the activity of absorption is under regulation of cell iron homeostasis.3.Anemia intervention verification of SCE through rats anemia model.Rats anemia model is set up through iron deficiency diet for rats, then SCE-Fe is added to diet for anemia intervention. The results indicate that after iron repletion period, every experimental indicators signally improved. Feed ration, body weight gain, hemoglobin concentration, hematocrit value and serum iron were not lower than ferrous suliate group, and much higher than ferric citrate group(P<0.01). The iron relative biological value of ferric citrate chelated with SCE(133.58%±15.42%) is obviously higher than ferrous sulfate(100%±14.84%) and ferric citrate(66.34%± 8.71%).In a word, siderophores from synechococcus sp. PCC 7002 can improve the ferric iron bioavailability availably, indicate that siderophores exracet can be used for iron fortification. |
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