嗜酸性氧化亚铁硫杆菌休止细胞保存时间及循环利用对施氏矿物生物合成的影响

Effects of storage time and recycling of resting Acidithiobacillus ferrooxidans cells on biogenic schwertmannite formation

利用嗜酸性氧化亚铁硫杆菌(Acidithiobacillus ferrooxidans,简称A.ferrooxidans)休止细胞促进FeSO4形成的施氏矿物具有纯度高比表面积大的特点,对去除水环境中有毒重(类)金属有重要作用.为提供施氏矿物规模化生产优化参数,本研究通过摇瓶试验探讨了休止细胞保存时间对其活力的影响,以及休止细胞再次循环利用对施氏矿物生物合成中Fe2+氧化率和矿物产量的影响.结果表明,新鲜制备的A.ferrooxidans菌休止细胞可在48h内将144mmol·-L1Fe2+(250mL体系)全部氧化成Fe3+,在高浓度SO42-存在下约有41.99%的Fe3+被转化成棕红色施氏矿物沉淀,矿物产量达到1.34g.当休止细胞在4℃保存达45d时,Fe2+氧化率与新鲜细胞相比下降5.61%,施氏矿物产量降低35.07%.二次利用的循环A.ferrooxidans菌氧化Fe2+的能力大幅下降,其氧化性能只占新鲜休止细胞的1/7,这主要是由菌体本身氧化活性下降和矿物吸附包裹部分A.ferrooxidans菌导致菌体数量下降两个原因所致.可见,新制备的A.ferrooxidans菌休止细胞应现制现用,在4℃、pH=2.5的酸水中保存时间不宜超过30d,A.ferrooxidans菌休止细胞可循环利用于施氏矿物的生物合成,但其效能仅为新鲜休止细胞的15%左右.

Schwertmannite biosynthesized by resting Acidithiobacillus ferrooxidans （A.ferrooxidans） with FeSO4 has high purity and specific surface area.It can play an important role in the removal of toxic heavy metals or metalloids in water environments.To provide the optimum parameters for industrial scale production of schwertmannite,the effects of storage time of resting A.ferrooxidans cells and reuse of the recycling cells on the strain growth and its ability to facilitate Fe2＋ oxidation andmineral formation were investigated in batch experiments.The results indicated that the fresh resting A.ferrooxidans cells harvested within 30 d could completely oxidize 144 mmol·L-1 Fe2＋ to Fe3＋ after 48 h in the system with initial pH=2.5.In the presence of excess SO2-4,about 41.99% of the ferrous iron was transformed into the brown-red schwertmannite,and themineral weight reached 1.34 g in a 250 mL system.Compared to fresh resting A.ferrooxidans cells,the Fe2＋ oxidation percentage by the relatively aged resting A.ferrooxidans cells stored for 45 d at 4℃ was decreased by 5.61%,and the schwertmannite weight was decreased by 35.07%.Furthermore,the reuse of resting A.ferrooxidans cells resulted in a significant reduction of Fe2＋ oxidation with only 1/7 of the Fe2＋ oxidation ability of fresh resting cells,which was attributed to the decline of oxidation ability of the reused cells and a decrease in cell density due to adsorption or encapsulation byminerals.Therefore,freshly-prepared resting A.ferrooxidans cells should be used or the storage time should not exceed 30 d in acidic solution at 4℃.The resting A.ferrooxidans cells could be recycled and used for the biosynthesis of schwertmannite,but the efficiency was only about 15% of newly-prepared resting cells.