Microbial catalyst for desulfurization of fossil fuels

• US 6,124,130 A
• Filed: 08/10/1998
• Issued: 09/26/2000
• Est. Priority Date: 08/10/1998
• Status: Expired due to Fees

• Current Assignee: Clean Diesel Technologies, Inc.
• Original Assignee: Clean Diesel Technologies, Inc.
• Inventors: Olson, Gregory J.
• Primary Examiner(s): Beisner, William H.
• Application Number:
  US09/131,685
• Time in Patent Office: 778 Days
• Field of Search: 435/29, 435/34, 435/252.34, 435/252.4, 435/253.2, 435/253.3, 435/262, 435/262.5, 435/282, 435/872, 435/874
• US Class Current: 435/282
• CPC Class Codes: C12N 1/205 Bacterial isolates
• CPC Class Codes: C12P 1/04 by using bacteria
• CPC Class Codes: C12P 3/00 Preparation of elements or inorganic compounds except carbon dioxide recovery of carbon dioxides as by-products C12F3/02
• CPC Class Codes: C12P 5/00 Preparation of hydrocarbons or halogenated hydrocarbons
• CPC Class Codes: C12P 7/22 aromatic
• CPC Class Codes: C12R 2001/01 Bacteria or Actinomycetales ; using bacteria or Actinomycetales
• CPC Class Codes: C12R 2001/365 Nocardia

Abstract

Sulfur is removed from fossil fuels containing sulfur by incubation of the fuel with microbes isolated and purified from soil or water that selectively extract the sulfur without apparently utilizing the fuel as a carbon or energy source. Preferred biodesulfurization microbes remove at least about 20% of the sulfur. The microbes are obtained in a multi-step screen that first selects microorganisms that utilize dibenzothiophene (DBT) as a sole source of sulfur, and then tests these in incubations with fossil fuels; organisms that desulfurize DBT without metabolizing the DBT phenyl ring structures and desulfurize fuels only when a second carbon source devoid of sulfur is present are identified and employed in desulfurization processes. Two cultures, CDT-4 and CDT-4b, were particularly efficacious in the desulfurization of liquid fossil fuels.

Claims

1. A biologically purified microbial co-culture, CDT-4, of species of Pseuclonionas, and a species of Nocardia asteroides, CDT-4b.

2. A method for removing sulfur from a fossil fuel containing sulfur comprising incubating the fuel with a culture according to claim 1 in a media comprising mineral nutrients and an assimilable carbon source devoid of sulfur for such time under such conditions to remove at least a portion of the sulfur in said fuel.

3. A method according to claim 2 wherein at least about 20% of the sulfur is removed in an incubation at about 25°

to 30°

C. for about fourteen to 24 days.

4. A method according to claim 2 wherein the media is a basal salts media and the assimilable carbon source is selected from the group consisting of glycerol, glucose, ethanol, and mixtures thereof.

5. A method according to claim 2 wherein the fossil fuel is liquid and the culture media is a liquid.

6. A method according to claim 5 wherein the fossil fuel is a petroleum distillate.

7. A method for removing sulfur from a liquid fossil fuel containing sulfur comprising incubating the fuel with a microbial cultures CDT-4 or CDT-4b in a liquid media comprising basal salt nutrients and an assimilable carbon source devoid of sulfur for such time under such conditions effective to remove at least a portion of the sulfur in the fuel.

8. A method according to claim 7 wherein at least about 20% of the sulfur is removed.

9. A screening method for identifying and purifying soil or water microorganisms that selectively remove sulfur from fossil fuels, which comprises:

(a) first isolating and biologically purifying microorganisms that will grow on dibenzothiophene as a sole source of sulfur by

(i) incubating a soil or water sample in a bacterial culture media containing inorganic nutrients, an assimilable carbon source devoid of sulfur, and dibenzothiophene as a sole source of sulfur for such time under such conditions sufficient to observe bacterial cell growth;

(ii) diluting a culture that grows by a factor of 1;

500 to 1;

2000 with fresh culture media at weekly intervals for at least three weeks to obtain an enriched culture;

(iii) streaking the culture on a solid culture medium and incubating for such time under such conditions to obtain bacterial cell growth of isolated colonies; and

(iv) restreaking isolated colonies to obtain biologically purified cultures of microorganisms that will grow on dibenzothiophene as a sole source of sulfur;

(b) then screening the biologically purified cultures in a first screen comprising the steps of;

(i) adding a purified culture from step (a) to media containing inorganic nutrients, an assimilable carbon source devoid of sulfur, and dibenzothiophene as a sole source of sulfur, thereby providing a sample culture;

(ii) adding the purified culture to a corresponding second media containing the same inorganic nutrients and carbon source, but no dibenzothiophene, thereby providing a control culture;

(iii) incubating the sample and control cultures for such time and under such conditions sufficient to observe bacterial cell growth;

(iv) comparing the extent of growth in the sample culture containing the dibenzothiophene with the extent of growth in the culture containing no dibenzothiophene;

(v) identifying any culture that grows in the sample culture containing dibenzothiophene but does not grow in the control culture containing no dibenzothiophene;

(vi) identifying the metabolic products of dibenzothiophene in any cultures that grows on dibenzothiophene; and

(vii) identifying as a positive first screen culture any culture that grows on dibenzothiophene and yields metabolic products comprising biphenyls or hydroxybiphenyls and substantially no other products containing carbon; and

then

(c) rescreening the positive cultures identified in (b) in a second screen comprising the steps of;

(i) inoculating, with a positive culture identified in screen (b), a bacterial culture media containing inorganic nutrients and a fossil fuel as a sole carbon and sulfur source;

(ii) inoculating, with the same positive culture, a corresponding second culture containing the same bacterial culture media, the same fossil fuel, and a second carbon source devoid of sulfur;

(iii) incubating the cultures for such time under such conditions sufficient to observe bacterial cell growth;

(iv) comparing the extent of growth in the culture containing the fossil fuel as the sole carbon source with the extent of growth in the culture containing the fossil fuel and a second carbon source;

(v) identifying a microorganism that selectively removes sulfur from fossil fuels by observing microbial growth in a culture in the presence of a fossil fuel and a second carbon source, and no growth of the corresponding culture incubated in the presence of the fossil fuel but no second carbon source.

10. A method according to claim 9 wherein only first screen positive test samples that desulfurize at least about 20% of the dibenzothiophenc in the first screen culture are tested in the second screen.

11. A method according to claim 9 wherein the incubations in both screens are conducted at about 25°

to 30°

C. for three to fourteen days.

12. A method according to claim 9 wherein the carbon source is selected from the group consisting of glycerol, glucose, ethanol, and mixtures thereof, and the media for both screens is a basal salts media.

13. A method according to claim 12 wherein the carbon source is glycerol.

14. A biological purified microbial culture of Nocardia asteroides, CDT-4b.