Biomineralization Of U???-PO₄^3-Promoted By Aspergillus Tubingensis Mediated Phytate Hydrolysis

The remediation of uranium-contaminated water is the focus of research in the field of the environment.During the cycle of nuclear fuel,a small amount of uranium is released into the environment,causing some water to be contaminated.The majority form of uranium was U(VI)in the uranium contaminated water,which is easy to migrate and poses a potential threat to the natural environment and human health.Compared with traditional remediation methods,in-situ biomineralization of uranium has the advantages of simple design,high practicability and little interference to the environment,and so on.It has a wider range of application and more stable products compared with bioreduction.Therefore,it is considered as one of the most promising remediation technologies for uranium-contaminated water.Usually,the synthetic organophosphorus such as G2P or G3P and the microorganisms capable of dissolving phosphorus are added to the uranium-contaminated water.The microorganisms produce phosphatase under the stress of uranium,which catalyzes the hydrolysis of organophosphorus to release orthophosphates,and then the orthophosphates react with uranium to form insoluble precipitates.Phytate,an economical and efficient natural organic phosphorus,can be hydrolyzed by phosphatase to lower inositol derivatives(IPX,x=1-5)and orthophosphates,may potentially yields six moles of orthophosphate per mole of phytate.In this study,phytate was used as organophosphorus source and the mineralization of U-PO43-promoted by the selected microorganism mediated phytate hydrolysis was investigated.In this study,the fungus M5-1 capable of hydrolyzing phytate was isolated from the sediments of a uranium tailings repository in Guangdong Province.Its colony morphology,ITS sequences,suitable growth pH value,tolerance against uranium and effect on hydrolysis of phytate were systematically studied.The variations of pH value,orthophosphate concentration,uranium concentration and removal efficiency of uranium were mo]itored.After biomineralization of U(?)-PO43" promoted by Aspergillus tubingensis mediated phytate hydrolysis for 62 days,the main elements,phase composition and valence state of uranium in the mineralized products were analyzed by SEM-EDS,XRD and XPS.It was found that the strain M5-1 was A.tubingensis(MH978623)with optimal growth at pH 6?7,and with high tolerance against uranium(?0.84 mmol/L).After biomineralization of U(?)-PO43-promoted by A.tubingensis mediated phytate hydrolysis for 62 days,the removal efficiency of uranium reached 95.2%.The mineralization products may contain U,P,Na,O and other elements.The mineralization products may be insoluble chernikovite and metanatroautunite,and the uranium in the mineralization products are all U(?).Therefore,A.tubingensis can effectively hydrolyze phytate and release soluble orthophosphate,and then promote the mineralization of U(?)-PO43-.These results provided an experimental basis for the in-situ bioremediation of uranium contaminated surface water by biomineralization of U(?)-PO43-promoted by A.tubingensis mediated phytate hydrolysis.