| Iron is an essential microelement in human body, required for vital metabolicfunctions. When iron available in the body is badly insufficient, iron deficiencyanaemia (IDA) develops. Oral iron supplementation, such as use of ferrous sulphate(FS), is the standard treatment for patients with IDA. However, due to the frequentgastrointestinal side effects, FS is hard to be accepted by the patients. Iron-enrichedyeast is regarded as a novel iron supplementation with good absorbability and minorgastrointestinal irritation. At the same time, it is an excellent source of proteins,essential amino acids and vitamins. Therefore, iron-enriched yeast is expected to playan important role in the treatment of IDA.The strain R6, which has potential iron accumulation ability, was selected outfrom40ΔSRE1disruptants of Aureobasidium pullulans HN6.2. It produced as high as12.2mg/g dw of extracellular and intracellular siderophores in iron sufficient mediumand these siderophores could be used for iron enrichment. By exploring theoptimizing time of iron addition, preliminary cultivation method of iron-enrichedyeast cells was obtained. Firstly, the strain R6was cultured in50mL of theiron-deplete medium to generate enough siderophores. Then,1.5mM FeCl3wasadded into the flask at the time of24h of the cultivation. After120hours’cultivation,the iron-enriched yeast cells were harvested. In this case, the iron content in theiron-enriched yeast reached11.9mg/g dw at flask level.The transcript levels of the SIDA gene encoding L-ornithine-N5-monooxygenasewhich catalyzes the first reaction for siderophore biosynthesis were analyzed usingreal-time PCR. It was found that in the iron sufficient medium, the relative transcriptlevel of the SIDA gene in R6strain (74.1%) was much higher than that of the SIDAgene in A. pullulans HN6.2(27.3%). This is reasonable that R6strain produces higher level of siderophore and accumulates more iron in the iron sufficient medium than thewide type HN6.2.The iron-enriched yeast was cultivated for120h in the1.5-L and6-Lfermentation medium, respectively. It was that the iron content in R6strain was5.15mg/g dw in1.5-L fermentation medium. To improve the amount of iron content in R6strain, the optimization for iron concentration was explored in50ml flask level and itwas found that the optimal concentration of iron was15mM. Then, the optimizediron concentration was used in6-L fermentation, and the iron content in R6strain wasincreased to27.79mg/g dw. Under these conditions, the amount of iron contentreached to26.59mg/g dw when the cultivation time was48h. In this case, theamount of the total sugar in the medium was very low. Therefore, the fermentationwas terminated at48h.The iron-enriched yeast was used for the treatment of IDA. Firstly, the safety ofthe iron-enriched yeast was assessed by the acute toxicity test. After each healthymouse received10g/kg of the iron-enriched yeast by intragastric administration, thesymptom of poisoning or death did not appear in the following14days, showing thatthe iron-enriched yeast was safe and non-toxic. The IDA model mice whosehemoglobin level and red blood cell numbers were reduced to89g/L and5.9×1012cells/L, respectively were obtained by feeding low-iron diets for4weeks. During themodeling process, every two days100μL of blood was removed from each mouse inorder to enhance iron deficiency anaemia. Compared with that of the normal mice, theweight of the IDA model mice was gained slowly, indicating that iron deficiencyaffected the normal growth of mice. The hemoglobin level and red blood cell numbersof the IDA model mice were restored to128g/L and7.5×1012cells/L, respectivelyafter10-days’ treatment with the iron-enriched yeast cells. It was found that theiron-enriched yeast significantly improved the hemoglobin level and red blood cellnumbers（P<0.05）of the IDA mice, demonstrating the iron-enriched yeasts have goodtherapeutic effect on iron deficiency anemia. |
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