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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
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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
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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
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50
S. thermosulfidooxidans
Fe/acid
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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
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60-75
T. thiooxidans
Acid
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25-40
T. acidophilus
Acid
3.0
25-30
T. caldus
Acid
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40-60
Fe/acid
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55-85
Thiobacillus ferrooxidans
T range (°C)
Sulfolobus solfataricus
(Archaean)
S. rivotincti
(Archaean)
Fe/acid
2.0
69
S. yellowstonii
(Archaean)
Fe/acid
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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:
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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
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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