Optimisation of biomineral precipitation in chemoorganotrophic systems for metal recovery

背景生物诱导的矿化在微生物中很常见(1)。真菌能够以不同的机制沉淀矿物质，包括氧化物、碳酸盐、磷酸盐和草酸盐，但都依赖于化学有机营养代谢以及不同的营养和环境条件(2-4)。在金属生物地球化学或生物回收方面，这类过程很少受到关注。通过控制生长条件，有可能促进金属生物沉淀，这提供了一种金属生物回收的手段。此外，生物矿物可以是纳米尺度的球形、纳米晶体、棒状和管状(1)。鉴于这种制剂的极高的表面积与体积比和反应性，这提供了进一步的应用兴趣。例如，草酸盐和碳酸盐在许多工业环境中都很重要，包括作为氧化物等其他有用化合物的前体。工业界寻求改进制造此类物质纳米级制剂的方法(5，6)。这一领域的信息十分匮乏，因此，这一博士项目提供了一个极好的机会来获取基础数据，增加对钴和其他金属的生物地球化学中的生物矿化作用的了解，以及在生物加工和生产有用的生物矿物产品中的应用意义。工作计划本项目将调查选定的地球活动真菌物种将钴生物矿化为不溶生物矿物质(主要是草酸盐、磷酸盐、碳酸盐)的能力，目的是表征和优化每个过程，以获得最大的产量。将对不同生物矿物系统的一系列营养和物理化学变量进行研究，如碳、氮源和pH，以及生物矿物沉淀涉及的机制。总体目标是优化所需生物矿物的最大产量，并了解能够在不同尺度(包括纳米和微米尺度)进行生物沉淀的条件。将确定从渗滤液中的金属混合物中选择性回收钴所需的条件，以及从溶液中获得其他沉淀物的可能性，如镍的沉淀物。学生将与PDRA一起工作，并将通过接收材料和渗滤液、矿石和渗滤液的化学分析以及与营养化学金属浸出和生物沉淀研究的结果比较，与其他研究小组直接互动。学生将接受有关地球微生物学和地球真菌学、环境地球化学和矿物学的跨学科培训，并将与其他正在进行的研究项目和培训网络互动，例如Geo-Rep-Net、地球微生物网络，涉及环境中金属的流动性。参考(1)GADD，G.M.金属，矿物和微生物：地球微生物学和生物修复。微生物学156,609-643(2010)。(2)GADD，G.M.地菌学：真菌对岩石、矿物、金属和放射性核素的生物地球化学转化、生物风化和生物修复。真菌学研究111，3-49(2007)。(3)Rhee，Y.J.，Hillier，S.&Gadd.，G.M.铅在真菌作用下转化为软锰矿。现代生物学22,237-241(2012)。(4)魏振中，梁晓星，彭德洛斯基，H.，希利尔，S.，Suntornvongsagul，K.，Sihanonth，P.&Gadd.，G.M.硅酸锌和硫化矿物的真菌生物转化.《环境微生物学》15,2173-2186(2013)。(5)Aimable，A.，Torres Puentes，A.&Bowen，P.通过草酸铜路线合成多孔和纳米结构的CuO粒子。粉末技术208,467-471(2011)。(6)基于混合模型的草酸钴合成过程中粒度分布的分批控制。《粉末技术》，224,253-259(2012)。

BackgroundBiologically-induced mineralization is common in microbes (1). Fungi are capable of precipitating minerals including oxides, carbonates, phosphates and oxalates by differing mechanisms but all dependent on chemoorganotrophic metabolism, and varying nutritional and environmental conditions (2-4). Such processes receive little attention in the contexts of metal biogeochemistry or biorecovery. Through manipulation of growth conditions, it is possible to promote metal bioprecipitation which provides a means of biorecovery of metals. Further, biominerals can be of nanoscale dimensions in spherical, nanocrystalline, rod and tube-like forms (1). This provides further applied interest in view of the very high surface area to volume ratio and reactivity of such preparations. Oxalates and carbonates, for example, are important in many industrial contexts including as precursors of other useful compounds, e.g. oxides. Industry seeks improved means of making nanoscale preparations of such substances (5,6). There is a dearth of information in this area and this PhD project therefore provides an excellent opportunity to obtain fundamental data and increase understanding of biomineralization in the biogeochemistry of Co and other metals, and applied significance in bioprocessing and production of useful biomineral products.WorkplanThis project will investigate the ability of selected geoactive fungal species to biomineralize Co as insoluble biominerals (primarily oxalates, phosphates, carbonates) with the aim being characterisation and optimisation of each process for maximum yield. A range of nutritional and physico-chemical variables, e.g. carbon and nitrogen source, and pH, will be investigated for the different biomineral systems, along with the mechanisms involved in biomineral precipitation. The overall objective is to optimise the maximal yield of desired biominerals, and to understand conditions that enable bioprecipitation at various scales including nano- and microscale. Conditions necessary for selective recovery of Co from metal mixtures in leachates will be determined, as well as the possibility of obtaining other precipitates from liquors, such as those of Ni. The student will work alongside the PDRA, and will directly interact with other research groups through receipt of materials and leachates, chemical analyses of ores and leachates, and comparison of results with chemolithotrophic metal leaching and bioprecipitation studies. The student will receive cross-disciplinary training in geomicrobiology and geomycology, environmental geochemistry and mineralogy, and will interact with other ongoing research projects and training networks, e.g. Geo-Rep-Net, Geomicrobiology Network, that are concerned with metal mobility in the environment.References(1) Gadd, G.M. Metals, minerals and microbes: geomicrobiology and bioremediation. Microbiology 156, 609 - 643 (2010).(2) Gadd, G.M. Geomycology: biogeochemical transformations of rocks, minerals, metals and radionuclides by fungi, bioweathering and bioremediation. Mycological Research 111, 3-49 (2007).(3) Rhee, Y.J., Hillier, S. & Gadd, G.M. Lead transformation to pyromorphite by fungi. Current Biology 22, 237-241 (2012).(4) Wei, Z., Liang, X., Pendlowski, H., Hillier, S., Suntornvongsagul, K., Sihanonth, P. & Gadd, G.M. Fungal biotransformation of zinc silicate and sulfide mineral ores. Environmental Microbiology 15, 2173-2186 (2013). (5) Aimable, A., Torres Puentes, A. & Bowen, P. Synthesis of porous and nanostructured particles of CuO via a copper oxalate route. Powder Technology 208, 467-471 (2011).(6) Zhang, S., Wang, F., He, D. & Jia, R. Batch-to-batch control of particle size distribution in cobalt oxalate synthesis process based on hybrid model. Powder Technology 224, 253-259 (2012).