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IN THE NAME OF GOD University of Esfahan Department of Biology Microbial Biotechnology Professor Nahvi Semester (II): 1386 – 87 Mineral Biotechnology Keivan Beheshti Maal May 2008 List of contents History of mineral biotechnology Bioremediation Bioremediation removable materials In situ bioremediation Transformation of Heavy Metals Source of heavy metals Heavy metal environmental and economical impact Microbe – heavy metal interactions Bioleaching Biosorption Enzymatic transformation Biomineralization Nuclear wastes History of mineral biotechnology 1954: Bryner, Oxidation of Iron pyrites and copper sulphide could by Thiobacillus spp. 1958: Zimmerley, the first patent for mineral biotechnology 1983: Groudev, remove of iron and silica from sands and bauxite ores by bacteria and fungi 1993: Ohmura, pyrite extraction by several bacteria 1997: Miller, use of mixed mesophilic bacteria for bioleaching plants 2001: Suzuki, Successful commercial metalleaching processes (extraction of gold, copper & uranium) Bioremediation Bioremediation is reclaiming or cleaning of contaminated sites using microbes or other organisms This entails the removal, degradation, or sequestering of pollutants & toxic wastes Bioremediation removable materials Oil spills Waste water Plastics Chemicals Toxic Metals Oil / Wastewater Cleanup In situ bioremediation Transformation of Heavy Metals Heavy Metals are toxic to life Disease Causing (i.e cancer) To alleviate man’s past mistakes Help Conserve habitable environment Ran out of Hole to dig for storage Contamination of water supply Sources of heavy metals in waste Mining Tailings Lead Plastics, fishing tools, batteries, cable sheeting Mercury Measurement and control devices Chromium Wood preservatives and pigments Nuclear Waste Heavy metals environmental impacts Lead Humans, slows nervous system Toxic to plant life Mercury Consumed in Fish Products, affects organs Cadmium Accumulates in kidneys Chromium Considered most toxic Heavy metals economical impacts Estimates of the current US market for metal bioremediation ~ 200 B$ / year The market for the clean-up of radioactive contamination ~ 140 B$ / year (2004) Current Techniques for Decontamination Ion exchange Electrodialysis Extraction Wells Metal-microbe interactions Bioleaching Biosorption Enzymatic Transformations Biomineralization Metal – microbe interactions Microbe assistance in mining for years Low-grade ore and mine tailings are exploited biologically Zinc, copper, nickel, cobalt, iron, tungsten, lead (sulfide: water insoluble) Conversion of sulfide to sulfate by M.O Leach out of the sulfates from ore / extraction Cu2S not soluble CuSO4 is soluble Metal – microbe interactions Bioleaching: conversion of insoluble metals to solubilize metal by microorganisms Adventages: - More cost effective - Low energy usage - Good function of M.O at low metal concentration - Harmless emissions - Reduced pollution in wastes Metal – microbe interactions Important mineral-decomposing M.Os: 1) Iron - oxidizing chemolithotrophs 2) Sulphur oxidizing chemolithotrophs E source: inorganic chemicals C source: CO2 (hydrogen, sulphur, iron-reducing bacteria / archaea) Metal-leaching microorganisms: use ferrous iron and reduced sulphur compounds as electron donors / CO2 fixation Produce sulphuric acid (acidophiles) Organism Metabolism obt pH 2.4 28-35 T. prosperus Anaerobe/ Fe/acid Halotolerant/ Fe/acid 2.5 30 Leptospirillum ferrooxidans Fe only 2.5-3.0 30 Sulfobacillus acidophilus Fe/acid ---- 50 S. thermosulfidooxidans Fe/acid ---- 50 L. thermoferrooxidans Fe 2.5-3.0 40-50 Acidianus brierleyi Acid 1.5-3.0 45-75 A. infernus Acid 1.5-3.0 45-75 A. ambivalens Acid 1.5-3.0 45-75 Sulfurococcus yellowstonii Fe/acid ---- 60-75 T. thiooxidans Acid ----- 25-40 T. acidophilus Acid 3.0 25-30 T. caldus Acid ----- 40-60 Fe/acid ----- 55-85 Thiobacillus ferrooxidans T range (°C) Sulfolobus solfataricus (Archaean) S. rivotincti (Archaean) Fe/acid 2.0 69 S. yellowstonii (Archaean) Fe/acid ----- 55-85 Thiobacillus - SRBs Highly specialized autotrophic bacterium Acidophile Iron oxidizer Fe2+ Fe3+ + e Electron acceptor: O2 Versatile: oxidizes sulfur, iron, copper….. oxidation of S0 generates sulfuric acid SRBs: Combined with Thiobacillus 2nd step: reverses metal mobilization Form insoluble metal sulfides Acid-mine drainage cleanup Commercial Bioleaching Tanks Biosorption Metabolism-independent sorption of heavy metals to biomass Negative charge at cell surface / metalbinding proteins Low cost Molecular biology tools: targeting engineered metal-binding proteins to cell surface Enzyme-Catalyzed Transformations Using enzymes from microorganisms to help treat metal contamination Examples: Metal precipitation Redox transformations Useing high valence metals as electron acceptors (Fe3+, Mn4+, U6+, Cr6+, Se6+, As5+) Metal immobilization (c-type cytochromes) Geobacter and Desulfovibrio Geobacter Anaerobic Subsurface iron reducer Reduces Fe3+ to Fe2+ Forms insoluble iron oxides Reduction of Uranium Electron donor: acetate c3 cytochrome: U(VI) reductase Uranium precipitated outside cell and in periplasm Desulfovibrio Sulfate reducer Reduction of uranium c3 cytochrome: U(VI) reductase Extracellular precipitation of uraninite (UO2) Reduction of chromate Again c3 cytochrome = Cr(VI) reductase Biomineralization Complete biodegradation of organic materials into inorganic constituents: CO2 or H20 SRBs Citrobacter Pseudomonas Biomineralization Iron-reducing bacteria Ex: Tc(VII) reduced abiotically by magnetite (Precipitation of TcO2 by SRBs) Combined with Thiobacillus (Precipitation of Hg, Cr, U) Citrobacter Phosphate Degradation of glycerol 2-phosphate phosphatase enzyme Concentration of metal phosphates at cell surface (Precipitation of uranium and cadmium) Biomineralization Pseudomonas fluorescens Chromate constitutive, membrane-associated metalloenzyme Tin (Sn) Secretion of soluble extracellular compound Pseudomonas syringae Copper periplasmic copper-binding proteins Nuclear Waste Current Treatment only by decay Storage Site away from civilization for Decay Leaking by Solublization into water Making heavy metals into insoluble form Bacteria precipitation of heavy metals Oxidized to a Reduced Form (less reactive) [Uranium (Vi), Cr (VI) To U (IV) , Cr (III)] Indirect Reduction SO42- to H2S Reduction of radioactive metal to insoluble state by H2S Toxic effects low rate of bioremdiation in M.O Radio active contamination effects Nuclear waste 120 sites in 36 states that contain nuclear waste 475 billion gallons of contaminated groundwater 75 million cubic meters of contaminated sediment 3 million cubic meters of leaking waste RA elements half-life Radioactive element Half life (years) Sr – 90 -------------------- 28 Cs – 137 -------------------- 30 Pu – 239 -------------------- 24100 Tc – 97 -------------------- 2.6 M U – 238 ------------------- 4.5 B U – 235 ------------------- 7.13 M Genetically Engineered Microbes Deinococcus radiodurans Radiation Resistant (up to 1.5 million rads) Bacillus infernos High temperature resistant Methanococcus jannaschii Pressure resistant (up to 230 atm) Treatable Heavy Metals Toxic Metals Uranium Chromium Selenium Lead (Pb) Technetium Mercury Other Metals Vanadium Molybdenum Copper Gold Silver Factors to be Considered Bioethics regarding Genetic Engineered Microbes Bioethics of Ecological Damage Control Cost / Tax Money Duration of Treatment to be effective Have a nice time Bioremediation of the Alaska shorelines