# US 5,352,608 A · Bioreduction of metal oxides and oxyanions by photosynthetic bacteria

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- Number: US 5,352,608 A
- Document ID: US5352608A
- Status: Granted
- Kind: A
- Application number: 07/820,116
- Filed: 1992-01-13
- Granted: 1994-10-04
- Earliest claimed: 1992-01-13
- Assignees: Board of Regents, The University of Texas
- Inventors: Samuel Kaplan; Mark D. Moore
- Web page: https://patentgrep.com/patent/US5352608A

## CPC

- C12N 1/00: Microorganisms; Compositions thereof (medicinal preparations containing material from protozoa, bacteria or viruses A61K35/66, from algae A61K36/02, from fungi A61K36/06; preparing medicinal bacterial antigen or antibody compositions, e.g. bacterial vaccines, A61K39/00); Processes of propagating, maintaining or preserving microorganisms or compositions thereof; Processes of preparing or isolating a composition containing a microorganism; Culture media therefor
- C02F 1/70: by reduction {(C02F1/4676 takes precedence)}
- C02F 3/34: characterised by the microorganisms used
- C12N 1/20: Bacteria; Culture media therefor
- C12N 1/205: Bacterial isolates
- C12P 3/00: Preparation of elements or inorganic compounds except carbon dioxide {(recovery of carbon dioxides as by-products C12F3/02)}
- C12R 2001/00: Microorganisms {; Processes using microorganisms}
- C12R 2001/01: Bacteria or Actinomycetales {; using bacteria or Actinomycetales}
- Y02W 10/37: using solar energy
- Y10S 423/17: Microbiological reactions
- C12N: MICROORGANISMS OR ENZYMES; COMPOSITIONS THEREOF; PROPAGATING, PRESERVING, OR MAINTAINING MICROORGANISMS; MUTATION OR GENETIC ENGINEERING; CULTURE MEDIA (microbiological testing media C12Q1/00)
- C02F: TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE (separation in general B01D; special arrangements on waterborne vessels of installations for treating water, waste water or sewage, e.g. for producing fresh water, B63J; adding materials to water to prevent corrosion C23F; treating radioactively-contaminated liquids G21F9/04; regeneration of reactants for recirculation into processes, see the relevant places for the processes)
- C12P: FERMENTATION OR ENZYME-USING PROCESSES TO SYNTHESISE A DESIRED CHEMICAL COMPOUND OR COMPOSITION OR TO SEPARATE OPTICAL ISOMERS FROM A RACEMIC MIXTURE {(brewing of beer C12C; producing vinegar C12J; producing specific peptides or proteins C07K; producing enzymes C12N9/00; DNA or RNA concerning genetic engineering, vectors, e.g. plasmids, or their isolation, preparation or purification C12N15/00; measuring or testing processes involving enzymes or microorganisms C12Q; measuring or testing processes involving nucleic acid amplification reactions C12Q1/6844; fermentation processes to form a food composition, A21 or A23; compounds in general, see the relevant compound class, e.g. C01, C07)}
- C12R: INDEXING SCHEME ASSOCIATED WITH SUBCLASSES C12C - C12Q, RELATING TO MICROORGANISMS
- Y02W: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

The invention relates to Proteobacteria that show unusually high level resistance to a wide range of metal oxides and oxyanions and to methods using selected subgroups for efficient reduction of certain metal oxides and oxyanions to the free metal. High level resistance was shown to be affected by growth conditions, and was observed in facultative photoheterotrophs such as Rhodobacter sphaeroides grown either chemoheterotrophically or photoheterotrophically.

## Claims

### Claim 1

A method for the reduction of a metal oxide or oxyanion, comprising contacting the metal oxide or oxyanion with a culture of photosynthetic Proteobacterium selected from a group consisting of Rhodobacter and Rhodopseudomonas in an aqueous medium under conditions facilitating reduction of the metal oxide or oxyanion by said Proteobacterium.

### Claim 2 (depends on 1)

The method of claim 1 wherein the Rhodobacter is R. sphaeroides or R. capsulatus.

### Claim 3 (depends on 1)

The method of claim 1 wherein the Rhodobacter is Rhodobacter sphaeroides 2.4.1 (ATCC 55398), 2.4.1.DELTA.S (ATCC 49848) or 2.4.7 (ATCC 17028).

### Claim 4 (depends on 1)

The method of claim 1 wherein the Rhodobacter is R. capsulatus B10 (ATCC 33303).

### Claim 5 (depends on 1)

The method of claim 1 wherein the metal oxide or oxyanion is reduced to free metal.

### Claim 6 (depends on 1)

The method of claim 1 wherein the metal oxide or oxyanion is a metal oxide or oxyanion of selenium, tellurium or rhodium.

### Claim 7 (depends on 6)

The method of claim 6 wherein the metal oxide or oxyanion of selenium, tellurium or rhodium is tellurate, tellurite, selenate, selenite or rhodium sesquioxide.

### Claim 8 (depends on 1)

The method of claim 1 wherein conditions facilitating reduction of the metal oxide or oxyanion comprise an aerobic environment.

### Claim 9 (depends on 1)

The method of claim 1 wherein conditions facilitating reduction of the metal oxide or oxyanion comprise an anaerobic environment.

### Claim 10 (depends on 1)

The method of claim 1 wherein conditions facilitating reduction of the metal oxide or oxyanion comprise minimal media having a carbon source in a low oxidation state.

### Claim 11 (depends on 10)

The method of claim 10 wherein the carbon source is butyrate, succinate or malate.

### Claim 12 (depends on 1)

The method of claim 1 wherein conditions facilitating reduction of the metal oxide or oxyanion comprise photoheterotrophic conditions.

### Claim 13 (depends on 12)

The method of claim 12 wherein photoheterotrophic conditions include an incident light intensity of between about 5 and 25 W/m.sup.2.

### Claim 14

A method of reducing a metal or nonmetal oxide or oxyanion in aqueous medium, comprising growing Rhodobacter under suitable aerobic or anaerobic conditions minimal media having a carbon source in a low oxidation state and contacting a sample containing the metal or nonmetal oxide or oxyanion with the Rhodobacter to allow reduction of said oxide or oxyanion by said Rhodobacter.

### Claim 15 (depends on 14)

The method of claim 14 wherein the carbon source is butyrate, succinate or malate.

### Claim 16 (depends on 14)

The method of claim 14 wherein the minimal media contains about 0.2 to about 0.8% by weight of the carbon source.

### Claim 17 (depends on 14)

The method of claim 14 wherein the metal or nonmetal is selected from a group consisting of silicon, molybdenum, arsenic, tungsten, tin, sulfur, antimony and vanadium.

### Claim 18

A method of reducing an oxide or oxyanion of a metal comprising the steps:
growing R. sphaeroides in an aerobic or anaerobic environment in minimal media:
contacting the R. sphaeroides with a sample containing a metal oxide or oxyanion under conditions suitable for reduction of the metal oxide or oxyanion by R. sphaeroides: and
isolating a R. sphaeroides cell or R. sphaeroides cell fraction which contains free metal resulting from reduction of said metal oxide or oxyanion.

### Claim 19 (depends on 18)

The method of claim 18 wherein the R. sphaeroides is 2.4.1 (ATCC 55398) or 2.4.1.DELTA.S (ATCC 49848).

### Claim 20 (depends on 18)

The method of claim 18 wherein the cell fraction containing the free metal is the cell cytoplasmic membrane fraction.

### Claim 21 (depends on 18)

The method of claim 18 wherein the metal is selected from a group consisting of gold, platinum, uranium, silver, palladium and titanium.

### Claim 22 (depends on 18)

The method of claim 18 wherein the metal is selected from a group consisting of tellurium, selenium, and rhodium.

### Claim 23 (depends on 18)

The method of claim 18 further comprising growing R. sphaeroides under photoheterotrophic conditions.

### Claim 24 (depends on 20)

The method of claim 20 wherein the isolating is by sucrose density gradient centrifugation of the cytoplasmic membrane fraction.

### Claim 25 (depends on 18)

The method of claim 18 wherein the sample is obtained from surficial sediments, groundwater, salina, estuarial salterns, farm drainage, streams, rivers, ponds, marine waters or littoral lakes.

### Claim 26

A method of isolating free metal from a solution containing an oxide or oxyanion of the metal, comprising:
reducing the metal oxide or oxyanion under conditions suitable for reduction of the metal oxide or oxyanion by the cytoplasmic membrane fraction of R. sphaeroides 2.4.1 (ATCC 55398) to produce free metal;
accumulating the free metal in said membrane fraction; and
separating the free metal from the membrane fraction in which the free metal has accumulated to obtain substantiality pure metal.