Patent Description:
A process is provided for bioconversion of carbon monoxide and carbon dioxide. More specifically, the process includes providing carbon monoxide and carbon dioxide containing gaseous streams to acetogenic bacteria. The process provides for high levels of carbon monoxide and carbon dioxide conversions and utilization of hydrogen.

Carbon dioxide and carbon monoxide generation occur from natural processes as well as industrial processes that include combustion of fossil fuels such as coal, oil and natural gas. Due in part to industrial processes, atmospheric carbon dioxide and carbon monoxide concentrations continue to increase. These increases in carbon dioxide and carbon monoxide concentrations may contribute to atmospheric changes which result in climate change and global warming. Carbon dioxide is difficult to utilize in biological processes because of its highly oxidized state.

In addition to carbon dioxide and carbon monoxide, many industrial processes also result in production of hydrogen. Hydrogen has a high level of reducing potential. However, hydrogen is difficult to store and utilize due to its very flammable nature.

In view of the large amount of carbon dioxide and carbon monoxide generated, there is a need for a bacterial fermentation system that can utilize both carbon monoxide and carbon dioxide.

A process includes providing a gaseous substrate Gx to a bioreactor Bx, the gaseous substrate Gx comprising CO<NUM> and contains about <NUM> to about <NUM> mole % CO<NUM>. Acetogenic bacteria Mx are provided to tire bioreactor Bx. The acetogenic bacteria Mx includes a sodium translocating ATPase that is active during fermentation in the bioreactor Bx. The process includes providing sodium ions to the bioreactor Bx through one or more sodium ion sources and fermenting the gaseous substrate Gx with the acetogenic bacteria Mx in a fermentation broth comprising the acetogenic bacteria Mx and the one or more sodium ion sources to produce one or more organic acids. The fermentation broth includes less than about <NUM> grams per liter yeast extract, less than about <NUM> grams per liter carbohydrate, and wherein the sodium ions are provided with a sodium feed rate of about <NUM> to about <NUM> ug/gram of cells/minute. The process includes maintaining the fermentation broth at a pH in a range of about <NUM> to about <NUM>. At least a portion of the one or more organic acids is provided to a bioreactor Bi. The process further includes providing gaseous substrate Gi to the bioreactor Bi, the gaseous substrate Gi comprising CO and contains about <NUM> to about <NUM> mole % CO. Acetogenic bacteria Mi is provided to bioreactor Bi. The acetogenic bacteria Mi includes a proton translocating ATPase that is active during fermentation in the bioreactor Bi. The process further includes fermenting the gaseous substrate Gi in the bioreactor Bi with the acetogenic bacteria Mi in a fermentation broth comprising the acetogenic bacteria Mi to produce a liquid stream comprising one or more alcohols and a gaseous stream Gp comprising CO<NUM>.

A process includes providing a gaseous substrate Gx to a bioreactor Bx, the gaseous substrate Gx comprising CO<NUM> and H<NUM> and contains about <NUM> to about <NUM> mole % CO<NUM>. Acetogenic bacteria Mx are provided to the bioreactor Bx. The acetogenic bacteria Mx includes a sodium translocating ATPase that is active during fermentation in the bioreactor Bx. The process includes providing sodium ions to the bioreactor Bx through one or more sodium ion sources and fermenting the gaseous substrate Gx with the acetogenic bacteria Mx in a fermentation broth comprising the acetogenic bacteria Mx and the one or more sodium ion sources to produce one or more organic acids. The fermentation broth includes less than about <NUM> grams per liter yeast extract, less than about <NUM> grams per liter carbohydrate and wherein the sodium ions are provided with a sodium feed rate of about <NUM> to about <NUM> ug/gram of cells/minute. The process includes maintaining the fermentation broth at a pH in a range of about <NUM> to about <NUM>. At least a portion of the one or more organic acids is provided to a bioreactor Bi. The process further includes providing gaseous substrate Gi to the bioreactor Bi, the gaseous substrate Gi comprising CO and contains about <NUM> to about <NUM> mole % CO. Acetogenic bacteria Mi is provided to bioreactor Bi. The acetogenic bacteria Mi includes a proton translocating ATPase that is active during fermentation in the bioreactor Bi. The process further includes fermenting the gaseous substrate Gi in the bioreactor Bi with the acetogenic bacteria Mi in a fermentation broth comprising the acetogenic bacteria Mi to produce a liquid stream comprising one or more alcohols and a gaseous stream Gp comprising CO<NUM>.

A process includes providing a gaseous substrate Gx to a bioreactor Bx, the gaseous substrate Gx comprising CO<NUM> and containing about <NUM> to about <NUM> mole % CO<NUM>. Acetogenic bacteria Mx are provided to the bioreactor Bx, wherein the acetogenic bacteria Mx includes a sodium translocating ATPase that is active during fermentation in the bioreactor Bx. The process includes providing sodium ions to the bioreactor Bx through one or more sodium ion sources and fermenting the gaseous substrate Gx with the acetogenic bacteria Mx in a fermentation broth comprising the acetogenic bacteria Mx and the one or more sodium ion sources to produce one or more organic acids. The fermentation broth includes less than about <NUM> grams per liter yeast extract, less than about <NUM> grams per liter carbohydrate, and wherein the sodium ions are provided with a sodium feed rate of about <NUM> to about <NUM>µg/gram of cells/minute. The process includes maintaining the fermentation broth at a pH in a range of about <NUM> to about <NUM>. At least a portion of the one or more organic acids to a bioreactor system Bi-s. The process further includes providing a gaseous substrate Gi to the bioreactor system Bi-s, the gaseous substrate Gi comprising CO and containing about <NUM> to about <NUM> mole % CO. Acetogenic bacteria Mi to bioreactor system Bi-s, wherein the acetogenic bacteria Mi includes a proton translocating ATPase that is active during fermentation in the bioreactor system Bi-s. The process further includes fermenting the gaseous substrate Gi in the bioreactor system Bi-s with the acetogenic bacteria Mi in a fermentation broth comprising the acetogenic bacteria Mi to produce a liquid stream comprising one or more alcohols and a gaseous stream Gp comprising CO<NUM>.

The following description is not to be taken in a limiting sense, but is made merely for the purpose of describing the general principles of exemplary embodiments. The scope of the disclosure should be determined with reference to the claims.

Unless otherwise defined, the following terms as used throughout this specification for the present disclosure are defined as follows and can include either the singular or plural forms of definitions below defined:.

The term "about" modifying any amount refers to the variation in that amount encountered in real world conditions, e.g., in the lab, pilot plant, or production facility. For example, an amount of an ingredient or measurement employed in a mixture or quantity when modified by "about" includes the variation and degree of care typically employed in measuring in an experimental condition in production plant or 1ab. For example, the amount of a component of a product when modified by "about" includes the variation between batches in multiple experiments in the plant or lab and the variation inherent in the analytical method. Whether or not modified by "about," the amounts include equivalents to those amounts. Any quantity stated herein and modified by "about" can also be employed in the present disclosure as the amount not modified by "about".

The term "fermentor" includes a fermentation device/bioreactor consisting of one or more vessels and/or towers or piping arrangements, which includes a batch reactor, semi-batch reactor, continuous reactor, continuous stirred tank reactor (CSTR), bubble column reactor, external circulation loop reactor, internal circulation loop reactor, immobilized cell reactor (ICR), trickle bed reactor (TBR), moving bed biofilm reactor (MBBR), gas lift reactor, membrane reactor such as hollow fibre membrane bioreactor (HFMBR), static mixer, gas lift fermentor, or other vessel or other device suitable for gas-liquid contact.

The terms "fermentation", fermentation process" or "fermentation reaction" and the like are intended to encompass both the growth phase and product biosynthesis phase of the process. In one aspect, fermentation refers to conversion of CO<NUM> to acetic acid. In another aspect, fermentation refers to conversion of CO to alcohol.

The term "cell density" means mass of microorganism cells per unit volume of fermentation broth, for example, grams/liter.

The term "specific CO<NUM> uptake" means an amount of CO<NUM> in mmoles consumed by unit mass of microorganism cells (g) per unit time in minutes, i.e. mmole/gram/minute. The term "specific CO uptake" means an amount of CO in mmoles consumed by unit mass of microorganism cells (g) per unit time in minutes, i.e. mmole/gram/minute.

As used herein, productivity is expressed as STY. In this aspect, alcohol productivity may be expressed as STY (space time yield expressed as g ethanol/(L·day) or (g acetic acid /(L·day).

As used herein, "oxygenated hydrocarbonaceous compounds" may include carbon, hydrogen and oxygen containing compounds, such as for example, ethanol and butanol.

Embodiments of the disclosure provide methods, systems, and compositions for producing and obtaining alcohol products and bacterial proteins derived from microbial cell biomass after an anaerobic bacterial fermentation process. In one embodiment, a system and a method of increasing carbon capture efficiency, reducing carbon dioxide footprint, and increasing alcohol product productivity are provided.

As shown in <FIG>, the system may include bioreactor Bi <NUM> being adapted to ferment a gaseous substrate Gi <NUM> with an acetogenic bacteria Mi. The gaseous substrate Gi <NUM> may include carbon monoxide (CO) and hydrogen gas (H<NUM>).

In one aspect, the fermentation of gaseous substrate Gi <NUM> in bioreactor Bi <NUM> results in a gaseous stream Gp <NUM>. Gaseous stream Gp <NUM> comprises carbon dioxide (CO<NUM>) and may include one or more gases selected from the group consisting of carbon monoxide (CO), hydrogen gas (H<NUM>), methane (CH<NUM>), nitrogen (N<NUM>) and combinations thereof. In this aspect, the gaseous stream Gp from bioreactor Bi <NUM> may include about <NUM> mole % to about <NUM> mole % CO, in another aspect, about <NUM> mole % to about <NUM> mole %, in another aspect, about <NUM> mole % to about <NUM> mole %, in another aspect, about <NUM> mole % to about <NUM> mole %, and in another aspect, about <NUM> mole % to about <NUM> mole % CO. Further, in another aspect, the gaseous stream Gp from bioreactor Bi <NUM> may include about <NUM> mole % to <NUM> mole% CO2, in still another aspect, about <NUM> mole % to <NUM> mole% CO<NUM>, in another aspect, <NUM> mole % to <NUM> mole % CO<NUM>, in another aspect, <NUM> mole % to <NUM> mole % CO<NUM>, in another aspect, <NUM> mole % to <NUM> mole % CO<NUM>, in another aspect, <NUM> mole % to <NUM> mole % CO<NUM>, in another aspect, <NUM> mole % to <NUM> mole % CO<NUM>, in another aspect, <NUM> mole % to <NUM> mole % CO<NUM>, in another aspect, <NUM> mole % to <NUM> mole % CO<NUM>, and in another aspect, <NUM> mole % to <NUM> mole % CO<NUM>.

As shown in <FIG>, the system may include a bioreactor Bx <NUM> adapted to ferment a gaseous substrate with an acetogenic bacteria Mx. Gaseous substrate Gx is provided to bioreactor Bx <NUM> at gas line <NUM>. In this aspect, gaseous stream Gp <NUM> from bioreactor Bi <NUM> may be provided directly to bioreactor Bx <NUM>. In another aspect, the system may include gas supplementation line <NUM> to provide additional gaseous substrate which is blended with gaseous stream Gp <NUM> to provide gaseous stream Gx <NUM> which is conveyed into bioreactor Bx <NUM>. Off-gas from bioreactor Bx <NUM> may be vented through vent line <NUM>. Both bioreactors are supplied with nutrient from nutrient supply tank <NUM>. Nutrient supply tank <NUM> may include multiple subunits to supply the same or different nutrients to each bioreactor.

In addition, the system may also include a fluid line <NUM> connecting bioreactor Bx <NUM> to bioreactor Bi <NUM> to deliver one or more acid compounds from bioreactor <NUM> Bx to bioreactor Bi <NUM>. The one or more acid compounds generated from bioreactor Bx <NUM> include C1 to C10 organic acids. Examples of C1 to C10 organic acids include acetic acid, formic acid, propionic acid, butyric acid, pentanoic (valeric acid) hexanoic acid, heptanoic acid, decanoic acid and combinations thereof. In one aspect, the acid compound from bioreactor Bx <NUM> that is delivered to bioreactor Bi <NUM> is effective for increasing alcohol production in bioreactor Bi <NUM>. In an aspect where the organic acid is acetic acid, gaseous substrate Gi <NUM> is provided to bioreactor Bi <NUM> to maintain an acetic acid concentration of about <NUM>/L or less in bioreactor Bi <NUM>. When gaseous substrate Gi is provided to lower the concentration of acetic acid, a concentration of butyric acid is also lowered. Therefore, acetic acid is used as a marker to maintain appropriate amounts of organic acids in bioreactor Bi. In another aspect, the organic acid feed rate is used to keep an acetic acid concentration of about <NUM>/L or less in bioreactor Bi <NUM>.

As further illustrated in <FIG>, cell permeate line <NUM> is configured to deliver permeate to a distillation tower <NUM> for separation of product <NUM> from permeate. Product may include an alcohol-containing product that comprises ethanol, butanol, and combinations thereof. Water (distillation bottoms) may be returned to bioreactor Bx <NUM> through water return line <NUM> and/or to bioreactor Bi <NUM> through water return line <NUM>.

<FIG> illustrates a more detailed aspect of a water recycle system. In this aspect, organic acid produced in bioreactor Bx <NUM> is conveyed through micro filtration <NUM> and further provided to bioreactor Bi <NUM> through fluid line <NUM>. At least a portion of cells may be returned from micro filtration <NUM> to bioreactor Bx <NUM> by cell recycle line <NUM>. Broth from bioreactor Bi <NUM> is conveyed through line <NUM> to microfiltration <NUM>. At least a portion of cells may be returned from microfiltration <NUM> to bioreactor Bi <NUM> by cell recycle line <NUM>. In some optional aspect, liquid from line <NUM> may go to ultrafiltration <NUM> and at least a portion of cells may be returned from ultrafiltration <NUM> to bioreactor Bi <NUM>. Liquid from ultrafiltration <NUM> is sent to distillation feed tank <NUM> and then to distillation tower <NUM>. Water (distillation bottoms) may be returned to bioreactor Bx <NUM> through water return line <NUM> and/or to bioreactor Bi <NUM> through water return line <NUM>.

In another aspect, as shown in <FIG>, a process may include bioreactor Bx <NUM> being adapted to ferment a gaseous substrate Gx <NUM> with an acetogenic bacteria Mx. The gaseous substrate Gx <NUM> may include carbon monoxide (CO) and hydrogen gas (H<NUM>) in addition to CO<NUM>. As shown in <FIG>, gaseous substrate Gx may be supplied to bioreactor Bx from bioreactor system Bi-s, which include two or more bioreactors Bi-n. As shown in <FIG>, Bi-n includes two bioreactors Bi <NUM>.

Gaseous substrate Gx <NUM> is provided to bioreactor Bx <NUM> at one or more gas lines. In this aspect, gaseous stream Gp <NUM> from the two or more bioreactors Bi <NUM> of bioreactor system Bi-s may be provided directly to bioreactor Bx <NUM>. In another aspect, the system may include gas supplementation lines <NUM> to provide additional gaseous substrate which is blended with gaseous stream Gp <NUM> to provide gaseous stream Gx <NUM> which is conveyed into bioreactor Bx <NUM>. Off-gas from bioreactor Bx <NUM> may be vented through vent line <NUM>. Each bioreactor may be supplied with nutrient from nutrients from one or more supply tank <NUM>. Nutrient supply tank <NUM> may include multiple subunits to supply the same or different nutrients to each bioreactor.

The bioreactor system Bi-s may include two or more bioreactors Bi <NUM> being adapted to ferment a gaseous substrate Gi <NUM> with an acetogenic bacteria Mi. The gaseous substrate Gi <NUM> may include carbon monoxide (CO) and hydrogen gas (H<NUM>), The fermentation of gaseous substrate Gi <NUM> in the bioreactors Bi <NUM> of bioreactor system Bi-s results in one or more gaseous streams Gp <NUM>. Gaseous stream Gp <NUM> comprises carbon dioxide (CO<NUM>) and may include one or more gases selected from the group consisting of carbon monoxide (CO), hydrogen gas (H<NUM>), methane (CH<NUM>), nitrogen (N<NUM>), and combinations thereof. In this aspect, the gaseous stream Gp from bioreactor Bi <NUM> may include about <NUM> mole % to about <NUM> mole % CO, in another aspect, about <NUM> mole % to about <NUM> mole %, in another aspect, about <NUM> mole % to about <NUM> mole %, in another aspect, about <NUM> mole % to about <NUM> mole %, and in another aspect, about <NUM> mole % to about <NUM> mole % CO. Further, in another aspect, the gaseous stream Gp from bioreactor Bi <NUM> may include about <NUM> mole % to <NUM> mole% CO<NUM>, in still another aspect, about <NUM> mole % to <NUM> mole% CO<NUM>, in another aspect, <NUM> mole % to <NUM> mole % CO<NUM>, in another aspect, <NUM> mole % to <NUM> mole % CO<NUM>, in another aspect, <NUM> mole % to <NUM> mole % CO<NUM>, in another aspect, <NUM> mole % to <NUM> mole % CO<NUM>, in another aspect, <NUM> mole % to <NUM> mole % CO<NUM>, in another aspect, <NUM> mole % to <NUM> mole % CO<NUM>, in another aspect, <NUM> mole % to <NUM> mole % CO<NUM>, and in another aspect, <NUM> mole % to <NUM> mole % CO<NUM>. In one aspect the gaseous substrate Gi <NUM> is provided to the two or more bioreactors Bi <NUM> (collectively referred to as Bi-n) to achieve a superficial gas velocity effective for producing about <NUM>% or less of a culture volume to foam per hour.

In addition, the system may also include two or more fluid lines <NUM> connecting bioreactor Bx <NUM> to bioreactor system Bi-s to deliver one or more acid compounds from bioreactor Bx <NUM> to bioreactor system Bi-s. In this aspect, bioreactor system Bi-s may include two or more bioreactors Bi <NUM> (two bioreactors Bi <NUM> are shown). The one or more acid compounds generated from bioreactor Bx <NUM> include C1 to C10 organic acids. Examples of C1 to C10 organic acids include acetic acid, formic acid, propionic acid, butyric acid, pentanoic (valeric acid) hexanoic acid, heptanoic acid, decanoic acid and combinations thereof. In one aspect, the acid compound from bioreactor Bx <NUM> that is delivered to bioreactor system Bi-s is effective for increasing alcohol production in bioreactor system Bi-s.

As further illustrated in <FIG>, cell permeate lines <NUM> are configured to deliver permeate to a distillation tower <NUM> for separation of product <NUM>. Product may include an alcohol-containing product that comprises ethanol, butanol, and combinations thereof. Water (distillation bottoms) may be returned to bioreactor Bx <NUM> through water return line <NUM> and/or to bioreactors Bi <NUM> through water return lines <NUM>.

CO-Containing Substrate: A CO-containing substrate (described as gaseous substrate Gi <NUM>) may include any gas that includes CO. In this aspect, a CO-containing gas may include syngas, industrial gases, and mixtures thereof. In a related aspect, a gaseous substrate provided to bioreactor Bi <NUM> may include in addition to CO, nitrogen gas (N<NUM>), carbon dioxide (CO<NUM>), methane gas (CH<NUM>), syngas, and combinations thereof.

Syngas may be provided from any known source. In one aspect, syngas may be sourced from gasification of carbonaceous materials. Gasification involves partial combustion of biomass in a restricted supply of oxygen. The resultant gas may include CO and H<NUM>. In this aspect, syngas will contain at least about <NUM> mole % CO, in one aspect, at least about <NUM> mole %, in one aspect, about <NUM> to about <NUM> mole %, in another aspect, about <NUM> to about <NUM> mole % CO, in another aspect, about <NUM> to about <NUM> mole % CO, in another aspect, about <NUM> to about <NUM> mole % CO, and in another aspect, about <NUM> to about <NUM> mole % CO. Some examples of suitable gasification methods and apparatus are provided in <CIT>, <CIT> and <CIT>, and in <CIT>, <CIT> and <CIT>, all of which were filed on March <NUM>.

In another aspect, the process has applicability to supporting the production of alcohol from gaseous substrates such as high volume CO-containing industrial gases. In some aspects, a gas that includes CO is derived from carbon containing waste, for example, industrial waste gases or from the gasification of other wastes. As such, the processes represent effective processes for capturing carbon that would otherwise be exhausted into the environment. Examples of industrial gases include gases produced during ferrous metal products manufacturing, non-ferrous products manufacturing, petroleum refining processes, gasification of coal, gasification of biomass, electric power production, carbon black production, ammonia production, methanol production, coke manufacturing and gas refonning.

In another aspect, H<NUM> may be supplied from industrial waste gases or from the gasification of other wastes. As such, the processes represent effective processes for capturing hydrogen that would otherwise be exhausted into the environment. Examples of industrial gases include gases produced during ferrous metal products manufacturing, non-ferrous products manufacturing, petroleum refining processes, gasification of coal, gasification of biomass, electric power production, carbon black production, ammonia production, methanol production and coke manufacturing. Other sources of hydrogen may include for example, H<NUM>O electrolysis and bio-generated H<NUM>.

Depending on the composition of the CO-containing substrate, the CO-containing substrate may be provided directly to a fermentation process or may be further modified to include an appropriate H<NUM> to CO molar ratio. In one aspect, CO-containing substrate provided to the fermentor has an H<NUM> to CO molar ratio of about <NUM> or more, in another aspect, about <NUM> or more, and in another aspect, about <NUM> or more. In another aspect, CO-containing substrate provided to the fermentor may include about <NUM> mole percent or more CO plus H<NUM> and about <NUM> mole percent or less CO, in another aspect, about <NUM> mole percent or more CO plus H<NUM> and about <NUM> mole percent or less CO, and in another aspect, about <NUM> mole percent or more CO plus H<NUM> and about <NUM> mole percent or less CO.

In one aspect, the CO-containing substrate includes CO and H<NUM>. In this aspect, the CO-containing substrate will contain at least about <NUM> mole % CO, in one aspect, at least about <NUM> mole %, in one aspect, about <NUM> to about <NUM> mole %, in another aspect, about <NUM> to about <NUM> mole % CO, in another aspect, about <NUM> to about <NUM> mole % CO, in another aspect, about <NUM> to about <NUM> mole % CO, and in another aspect, about <NUM> to about <NUM> mole % CO.

In one aspect, a gas separator is configured to substantially separate at least one portion of the gas stream, wherein the portion includes one or more components. For example, the gas separator may separate CO<NUM> from a gas stream comprising the following components: CO, CO<NUM>, H<NUM>, wherein the CO<NUM> may be passed to CO<NUM> storage and the remainder of the gas stream (comprising CO and H<NUM>) may be passed to a bioreactor. Any gas separator known in the art may be utilized. In this aspect, syngas provided to the fermentor will have about <NUM> mole % or less CO<NUM>, in another aspect, about <NUM> mole % or less CO<NUM>, and in another aspect, about <NUM> mole % or less CO<NUM>.

Certain gas streams may include a high concentration of CO and low concentrations of H<NUM>, In one aspect, it may be desirable to optimize the composition of the substrate stream in order to achieve higher efficiency of alcohol production and/or overall carbon capture. In another aspect, the concentration of H<NUM> in the substrate stream may be increased before the stream is passed to the bioreactor.

According to particular aspects of the disclosure, streams from two or more sources can be combined and/or blended to produce a desirable and/or optimized substrate stream. For example, a stream comprising a high concentration of CO, such as the exhaust from a steel mill converter, can be combined with a stream comprising high concentrations of H<NUM>, such as the off-gas from a steel mill coke oven.

Depending on the composition of the gaseous CO-containing substrate, it may also be desirable to treat it to remove any undesired impurities, such as dust particles before introducing it to the fermentation. For example, the gaseous substrate may be filtered or scrubbed using known methods.

Bioreactor Design and Operation: Descriptions of fermentor designs are described in <CIT> and <CIT>, and <CIT>.

In accordance with one aspect, the fermentation process is started by addition of medium to the reactor vessel. Some examples of medium compositions are described in <CIT> and <CIT>, and in <CIT>. The medium may be sterilized to remove undesirable microorganisms and the reactor is inoculated with the desired microorganisms. Sterilization may not always be required.

Concentrations of various medium components for use in bioreactor Bi <NUM> with acetogenic bacteria Mi are as follows:.

The ability of certain acetogens to utilize CO is due in part to the presence of a proton or hydrogen pump, also referred to as a proton translocating ATPase. Both proton translocating ATPase and sodium translocating ATPase are described in <NPL>. The term proton translocating ATPase may be used interchangeably with the term proton dependent ATPase and the term sodium translocating ATPase may be used interchangeably with the term sodium dependent ATPase. Hence, in one aspect, the process includes conducting fermentations in the fermentation bioreactor with acetogenic bacteria Mi that include a proton translocating ATPase. Examples of useful acetogenic bacteria Mi include those of the genus Clostridium, such as strains of Clostridium ljungdahlii, including those described in <CIT>, <CIT>, <CIT>, <CIT>and <CIT>, <CIT> and <CIT>, strains of Clostridium autoethanogenum (DSM <NUM> and DSM <NUM> of DSMZ, Germany) including those described in <CIT> and <CIT> and Clostridium ragsdalei (Pl <NUM>, ATCC BAA-<NUM>) and Alkalibaculum bacchi (CP11, ATCC BAA-<NUM>) including those described respectively in <CIT> and "<NPL> and Clostridium carboxidivorans (ATCC PTA-<NUM>) described in <CIT>. Other suitable microorganisms includes those of the genus Moorella, including Moorella sp. HUC22-<NUM>, and those of the genus Carboxydothermus. Mixed cultures of two or more microorganisms may be used.

Additional examples of useful acetogenic bacteria Mi include Acetogenium kivui, Acetoanaerobium noterae, Acetobacterium woodii, Alkalibaculum bacchi CP11 (ATCC BAA-<NUM>), Blautia producta, Butyribacterium methylotrophicum, Caldanaerobacter subterraneous, Caldanaerobacter subterraneous pacificus, Carboxydothermus hydrogenoformans, Clostridium aceticum, Clostridium acetobutylieum, Clostridium acetobutylicum P262 (DSM <NUM> of DSMZ Germany), Clostridium autoethanogenum (DSM <NUM> of DSMZ Germany), Clostridium autoethanogenum (DSM <NUM> of DSMZ Germany), Clostridium autoethanogenum (DSM <NUM> of DSMZ Germany), Clostridium autoethanogenum (DSM <NUM> of DSMZ Germany), Clostridium carboxidivorans P7 (ATCC PTA-<NUM>), Clostridium coskatii (ATCC PTA-<NUM>), Clostridium drakei, Clostridium ljungdahlii PETC (ATCC <NUM>), Clostridium ljungdahlii ERI2 (ATCC <NUM>), Clostridium ljungdahlii C-<NUM> (ATCC <NUM>). Clostridium Utifigdahlii <NUM>-<NUM> (ATCC <NUM>), Clostridium magnum, Clostridium pasteurianum (DSM <NUM> of DSMZ Germany), Clostridium ragsdalei P11 (ATCC BAA-<NUM>), Clostridium scatologenes, Clostridium thermoaceticum, Clostridium ultunense, Desulfotomaculum kuznetsovii, Eubacterium limosuin, Geobacter sulfurreducens, Methanosarcina acetivorans, Methanosarcina barkeri, Moorella thermoacetica, Moorella thermoautotrophica, Oxobacter pfennigii, Peptostreptococcus productus, Ruminococcus productus, Thermoanaerobacter kivui, Clostridium Stick-landii, and mixtures thereof.

The fermentation should desirably be carried out under appropriate conditions for the desired fermentation to occur (e.g. CO-to-ethanol). Reaction conditions that should be considered include pressure, temperature, gas flow rate, liquid flow rate, medium pH, medium redox potential, agitation rate (if using a stirred tank reactor), inoculum level, maximum gas substrate concentrations to ensure that CO in the liquid phase does not become limiting, and maximum product concentrations to avoid product inhibition.

Startup: Upon inoculation, an initial feed gas supply rate is established effective for supplying the initial population of microorganisms. Effluent gas is analyzed to determine the content of the effluent gas. Results of gas analysis are used to control feed gas rates. In this aspect, the process provides a calculated CO quantities (mmoles) to initial cell density (grams/liter) ratio of about <NUM> to about <NUM>, in another aspect, about <NUM> to about <NUM>, in another aspect, about <NUM> to about <NUM>, in another aspect, about <NUM> to about <NUM>, in another aspect, about <NUM> to about <NUM>, and in another aspect, about <NUM> to about <NUM>.

In another aspect, a fermentation process includes providing syngas to a fermentation medium in an amount effective for providing an initial calculated CO concentration in the fermentation broth of about <NUM> to about <NUM>, in another aspect, about <NUM> to about <NUM>, in another aspect, about <NUM> to about <NUM>, in another aspect, about <NUM> to about <NUM>, and in another aspect, about <NUM> to about <NUM>. Dissloved CO was calculated using Henry's law and the kLa of the reactor. The process is effective for increasing cell density as compared to a starting cell density.

As used herein, target cell density means a cell density of about to about <NUM> grams/liter or more, in another aspect, about <NUM> to about <NUM> grams/liter, in another aspect, about <NUM> to about <NUM> grams/liter, in another aspect, about <NUM> to about <NUM> grams/liter, in another aspect, about <NUM> to about <NUM> grams/liter, in another aspect, about <NUM> to about <NUM> grams/liter, in another aspect, about <NUM> to about <NUM> grams/liter, in another aspect, about <NUM> to about <NUM> grams/liter, and in another aspect, about <NUM> to about <NUM> grams/liter.

Post-startup: Upon reaching desired levels, liquid phase and cellular material is withdrawn from the reactor and replenished with medium. In post-startup, cell density will remain at constant levels.

CC<NUM>-Containing Substrate: In one aspect, the process includes providing a CO<NUM>-containing gaseous substrate (described as gaseous substrate Gx <NUM>) to a bioreactor. A CO<NUM>-containing substrate may include any gas that includes CO<NUM>. In this aspect, a CO<NUM>-containing gas may include industrial gases, fermentor gas streams including for example, fermentor off-gases and mixtures thereof. In a related aspect, the CO<NUM>-containing substrate may include hydrogen or it may be blended with a hydrogen source to provide desired levels and ratios of H<NUM> to CO<NUM>.

Industrial gases: In one aspect, the process includes providing a CO<NUM>-containing substrate to a bioreactor where the CO<NUM>-containing substrate is generated from industrial gases. Some examples of industrial gases include steel mill gas, industrial gas and incinerator exhaust gas. Examples of industrial gases include gases produced during ferrous metal products manufacturing, non-ferrous products manufacturing, petroleum refining processes, gasification of coal, gasification of biomass, electric power production, carbon black production, ammonia production, methanol production and coke manufacturing. Sources of hydrogen may include fossil fuels, steam reforming, oxidation of methane, coal gasification, and water electrolysis.

Depending on the composition of the gaseous CO<NUM>-containing substrate, it may also be desirable to treat it to remove any undesired impurities, such as dust particles before introducing it to the fermentation. For example, the gaseous substrate may be filtered or scrubbed using known methods. Further, depending on the composition of the gaseous CO<NUM>-containing substrate, the process may include adjusting the CO<NUM>-containing substrate to increase or decrease concentrations of CO<NUM> and/or H<NUM> to fall within desired ranges.

Ferrnentor gas streams: In one aspect, the process includes providing a CO<NUM>-containing substrate to a bioreactor where the CO<NUM>-containing substrate is a fermentor gas stream. Some examples of fermentor gas streams include fermentor off-gas generated in the fermentation of syngas. Some examples of syngas fermentation are described in <CIT>, which is incorporated herein by reference.

In one aspect, the process has applicability to supporting the production of alcohol from gaseous substrates such as high volume CO-containing industrial gases. In some aspects, a gas that includes CO is derived from carbon containing waste, for example, industrial waste gases or from the gasification of other wastes. The fermentation of CO-containing gas may result in CO<NUM> in fermentor off-gas. As such, the processes represent effective processes for capturing carbon that would otherwise be exhausted into the environment. In this aspect, the off-gas from the fermentation of CO-containing gas may include about <NUM> mole % to about <NUM> mole % CO.

Blending of gas streams: According to particular aspects, streams from two or more sources can be combined and/or blended to produce a desirable and/or optimized substrate stream. For example, a stream comprising a high concentration of CO<NUM>, such as the exhaust from a steel mill, can be combined with a stream comprising high concentrations of H<NUM>, such as the off-gas from a steel mill coke oven.

Depending on the composition of the CO<NUM>-containing substrate, the CO<NUM>-containing substrate may be provided directly to a fermentation process or may be further modified to include an appropriate H<NUM> to CO<NUM> molar ratio. The CO<NUM>-containing substrate may include from about <NUM> to about <NUM> mole % CO<NUM> and from about <NUM> to about <NUM> mole % H<NUM>. In one aspect, the CO<NUM> containing gas stream includes about <NUM> to about <NUM>% CO<NUM>.

In another aspect, the CO<NUM>-containing substrate provided to bioreactor Bx <NUM> may include from about <NUM> mole % to about <NUM> mole % CO, in another aspect, about <NUM> mole % CO to about <NUM> mole % CO, in another aspect, about <NUM> mole % CO to about <NUM> mole % CO, and in another aspect, about <NUM> mole % CO to about <NUM> mole % CO.

In one aspect, the acetogenic bacteria will have a molar ratio of consumption of H<NUM> to CO<NUM> at a ratio of about <NUM>:<NUM> to about <NUM>:<NUM>. Hence, any substrate gas provided to the bioreactor that includes H<NUM> and CO<NUM> can be utilized. However, optimal levels of substrate gas provided to the bioreactor will have a ratio of H<NUM> to CO<NUM> of about <NUM>:<NUM> to about <NUM>:<NUM>, in another aspect, about <NUM>:<NUM>, and in another aspect, about <NUM>:<NUM> to about <NUM>:<NUM>.

The fermentation should desirably be carried out under appropriate conditions for the desired fermentation to occur (e.g. CO<NUM>-to-acetic acid). Reaction conditions to be considered include pressure, temperature, gas flow rate, liquid flow rate, medium pH, agitation rate (if using a stirred tank reactor), inoculum level, and maximum acetic acid concentration to avoid product inhibition. In this aspect, the process includes reaction conditions in the following ranges:.

Acetogenic Bacteria: In one aspect, the microorganisms utilized include anaerobic acetogenic bacteria Mx that include a sodium pump which may also be described as sodium-translocating ATPases (for membrane bioenergetics). Sodium translocating ATPase are described in <NPL>. Acetogens that include a sodium-translocating ATPase require about <NUM> ppm NaCl in their growth medium for growth. To determine if an acetogen includes a sodium-translocating ATPase, the acetogen is inoculated into serum bottles containing about <NUM> to about <NUM> of growth medium with about <NUM> to about <NUM> ppm NaCl. Normal growth at NaCl concentrations of about <NUM> ppm or more means that the acetogen includes a sodium-translocating ATPase.

In this aspect, suitable acetogenic bacteria Mx include Acetobacterium bacteria, Acetogenium kivui, Acetoanaerobium noterae, Acetobacterium ivoodii, Alkalibaculum bacchi CPl l (ATCC BAA-<NUM>), Moorella thermoacetica, Moorella thermoautotrophica, Ruminococcus productus. Acetogenium kivui, and combinations thereof. In another aspect, the microorganism is Acetobacterium woodii,.

Medium Compositions and Control of Medium Feed Rates: In accordance with one aspect, the fermentation process is started by addition of a suitable medium to the reactor vessel. The liquid contained in the reactor vessel may include any type of suitable nutrient medium or fermentation medium. The nutrient medium will include vitamins and minerals effective for permitting growth of the microorganism being used. Sterilization may not always be required.

Concentrations of various medium components for use in bioreactor Bx <NUM> with acetogenic bacteria Mx are as follows:.

Process operation maintains a pH in a range of about <NUM> to about <NUM>, in another aspect, about <NUM> to about <NUM>, in another aspect about <NUM> to about <NUM>, and in another aspect, about <NUM> to about <NUM>. The medium includes less than about <NUM>/L yeast extract and less than about <NUM>/L carbohydrates.

The composition also includes a sodium ion concentration of about <NUM> to about <NUM> mmol per liter, in another aspect, about <NUM> to about <NUM> mmol per liter and in another aspect, a sodium ion concentration of about <NUM> to about <NUM> mmol per liter. In one aspect, the sodium ion concentration is about <NUM> ppm to about <NUM> ppm, in another aspect, about <NUM> ppm to about <NUM> ppm, in another aspect, about <NUM> ppm to about <NUM> ppm, in another aspect, about <NUM> to about <NUM> ppm Na, and in another aspect, about <NUM> to about <NUM> ppm Na. The sodium ion source is provided by a compound selected from the group consisting of sodium chloride, sodium hydroxide, sodium phosphate, sodium sulfate, sodium nitrate, sodium bicarbonate, sodium bisulfate and mixtures thereof.

The composition includes a source of molybdenum. In this aspect the molybdenum concentration is about <NUM>µg/L to about <NUM>µg/L, and in another aspect, about <NUM>µg/L to about <NUM>µg/L. Sources of molybdenum include Na<NUM>MoO<NUM>, CaMoO<NUM>, FeMoO<NUM> and mixtures thereof.

The composition may also include a complexing agent. In this aspect, a complexing agent may be included in the composition when the composition has a pH of about <NUM> or greater. The complexing agent may include ethylenediaminetetraacetic acid (EDTA), ethylenediamine diacetic acid (EDDA), ethylenediamine disuccinic acid (EDDS) and mixtures thereof.

The composition may include one or more of a source of NH<NUM>+, P, K, Fe, Ni, Co, Se, Zn, or Mg. Sources of each of these elements may be as follows.

NH<NUM> : The nitrogen may be provided from a nitrogen source selected from the group consisting of ammonium hydroxide, ammonium chloride, ammonium phosphate, ammonium sulfate, ammonium nitrate, and mixtures thereof.

P: The phosphorous may be provided from a phosphorous source selected from the group consisting of phosphoric acid, ammonium phosphate, potassium phosphate, and mixtures thereof.

K: The potassium may be provided from a potassium source selected from the group consisting of potassium chloride, potassium phosphate, potassium nitrate, potassium sulfate, and mixtures thereof.

Fe: The iron may be provided from an iron source selected from the group consisting of ferrous chloride, ferrous sulfate, and mixtures thereof.

Ni: The nickel may be provided from a nickel source selected from the group consisting of nickel chloride, nickel sulfate, nickel nitrate, and mixtures thereof.

Co: The cobalt may be provided from a cobalt source selected from the group consisting of cobalt chloride, cobalt fluoride, cobalt bromide, cobalt iodide, and mixtures thereof.

Se: The selenium may be provided from Na<NUM>SeO<NUM>, C<NUM>H<NUM>NO<NUM>Se, and mixtures thereof.

Zn: The zinc may be provided from ZnSO<NUM>.

W: The tungsten may be provided from a tungsten source selected from the group consisting of sodium tungstate, calcium tungstate, potassium tungstate, and mixtures thereof.

Mg: The magnesium may be provided from a magnesium source selected from the group consisting of magnesium chloride, magnesium sulfate, magnesium phosphate, and mixtures thereof.

S: The composition may also include sulfur. The sulfur may be provided from a sulfur source selected from the group consisting of cysteine, sodium sulfide, NaHS, NaH<NUM>S and mixtures thereof.

Startup: Upon inoculation, an initial feed gas supply rate is established effective for supplying the initial population of microorganisms. Effluent gas is analyzed to determine the content of the effluent gas. Results of gas analysis are used to control feed gas rates. In this aspect, the process provides a minimal cell density of about <NUM> grams per liter. In another aspect, the process provides a calculated CO<NUM> quantities per unit time (mmol/min) to initial cell density (grams/liter) ratio of about <NUM> to about <NUM>, and in another aspect, about <NUM> to about <NUM>.

In one aspect, nutrients may be added to the culture to increase cell growth rates. Suitable nutrients may include non-carbohydrate fractions of yeast extract.

Post-startup: Upon reaching desired levels, liquid phase and cellular material is withdrawn from the reactor and replenished with medium. The fermentation process is effective for increasing cell density as compared to a starting cell density. In this aspect, the process provides an average cell density of about <NUM> to about <NUM> grams/liter, in another aspect, about <NUM> to about <NUM> grams/liter, in another aspect, about <NUM> to about <NUM> grams/liter, in another aspect, about <NUM> to about <NUM> grams/liter, in another aspect, about <NUM> to about <NUM> grams/liter, and in another aspect, about <NUM> to about <NUM> grams/liter.

Production of Organic Acid: In another aspect, the process provides a source of C1 to C10 organic acids. In this aspect, the process may include obtaining acid product or products from the fermentation liquid broth. In this aspect, provides a specific organic acid productivity of about <NUM> to about <NUM> grams organic acid/liter/day/g cells, in another aspect, about <NUM> to about <NUM> grams organic acid/liter/day/g cells, in another aspect, about <NUM> to about <NUM> grams organic acid/liter/day/g cells, in another aspect, about <NUM> to about <NUM> grams organic acid/liter/day/g cells, in another aspect, about <NUM> to about <NUM> grams organic acid/liter/day/g cells and in another aspect, about <NUM> to about <NUM> grams organic acid/liter/day/g cells. In one aspect, the organic acid is acetic acid or butyric acid, or a mixture of both.

Conversions of CO<NUM> and H<NUM>: The process is effective for providing a CO<NUM> uptake of about <NUM> to about <NUM> mmol CO<NUM>/minute/gram dry cells, an H<NUM> uptake of about <NUM> to about <NUM> mmol H<NUM>/minute/gram dry cells. The process is effective for providing about <NUM> to about <NUM>% conversion of CO<NUM>, in another aspect, about <NUM> to about <NUM>% conversion of CO<NUM>, and in another aspect, about <NUM> to about <NUM>% conversion of CO<NUM>. In another aspect, the process is effective for providing about <NUM> to about <NUM>% conversion of H<NUM>, in another aspect, about <NUM> to about <NUM>% conversion of H<NUM>, and in another aspect, about <NUM> to about <NUM>% conversion of H<NUM>.

<FIG> shows a graph of CO<NUM> conversion <NUM> and H<NUM> conversion <NUM> by Acetobacterium woodii. A graphical illustration of acetic acid production <NUM> and its moving average <NUM>, and cell density <NUM> versus time is shown in <FIG>.

An initial lyophilized pellet of Acetobacterium woodii was obtained from German culture collection DSMZ, strain ID DSM-<NUM>. Culture was initially revived from lyophilized pellet using rich medium (fructose and yeast extract). An adaptation method was used to remove fructose from serum bottle medium where concentration of fructose in growth medium was stepped down <NUM>%, <NUM>%, <NUM>%. Growth rate and gas usage was used as an indicator of adaptation. (approximately <NUM> weeks). Preliminary pH adaptation work in serum bottles reduced required pH from <NUM> to <NUM> (<NUM> weeks). At this point, culture was amplified and inoculated into a reactor. In a reactor culture was further adapted to grow in lower pH of <NUM> to <NUM>.

A synthesis gas containing CO<NUM> and H<NUM> was continuously introduced into a stirred tank bioreactor containing Acetobacterium woodii, along with a liquid medium containing vitamins, trace metals, cysteine (as sulfur source), and salts as described herein.

A New Brunswick Bioflow <NUM> reactor containing the fermentation medium was started with actively growing Acetobacterium woodii. The rate of agitation of the reactor was set to <NUM> rpm. This agitation rate was increased throughout the experiment from <NUM> to <NUM> rpm. Feed gas flow to the reactor was increased from an initial at <NUM>/min to <NUM>/min. Temperature in the bioreactor was maintained at <NUM> throughout the experiment. Samples of gas feed into the bioreactor and off-gas from the bioreactor and fermentation broth in the bioreactor were taken at intervals, for example feed gas, off-gas and fermentation broth were sampled about daily, once two hours and once four hours respectively. Above samples were analyzed for consumption or production of various gas components, broth acetic acid concentration, and the optical density (cell density) of the culture. The unaroused volume of the reactor was maintained between <NUM> to <NUM> throughout the experiment. Also, the gas flow to the reactor was maintained at required gas flow rates by using a mass flow controller. The feed syngas composition was <NUM>% H<NUM>, <NUM>% CO2 and <NUM>% N2. This experiment was concluded when stable operation was reached.

A cell recycle system (CRS) was attached to the reactor before the start of the experiment. During the experiment, the rate of flow of nutrients (growth medium) to the reactor was as indicated in the Table. Medium feed rate was maintained throughout the experiment. The base (<NUM> NaOH) feed rate for pH control was <NUM>-<NUM>/min, and through the CRS, <NUM> - <NUM>/min permeate was drawn out from the reactor.

H<NUM> and CO<NUM> in the feed gas was fixed into cell material and acetic acid. The removal of H<NUM> and CO<NUM> was calculated by comparing inlet gas composition with the effluent gas composition. Component gas uptake is expressed in % of gas molecules converted by bacteria. In this experiment the following conversions were achieved; H<NUM>: <NUM>% - <NUM>%, CO<NUM>: <NUM>% - <NUM>%. In this experiment the rate of acetic acid production was <NUM>-<NUM> gllicjay.

Results can be summarized as follows:
<IMG>.

A gas containing CO<NUM> and H<NUM> was continuously introduced into a stirred tank bioreactor containing Acetobacterium woodii, along with a conventional liquid medium containing vitamins, trace metals, and salts. Fermentations were started as described in Example <NUM> and then continued to stable operation. In this Example, the feed gas included <NUM> mole % CO.

<FIG> and <FIG> describe growth of Acetobacterium woodii in the presence of <NUM>% CO. <FIG> illustrates cell density <NUM> and specific acetic acid productivity <NUM> versus time. <FIG> illustrates H<NUM> conversion <NUM>, CO conversions <NUM>, CO<NUM> conversions <NUM>, and cell density <NUM>.

A gas stream containing CO<NUM> and H<NUM> was continuously introduced into a stirred tank bioreactor containing Acetobacterium Woodii, along with a growth medium as described herein.

A New Brunswick Bioflow <NUM> reactor containing fermentation medium was started with actively growing Acetobacterium woodii (AW). The rate of agitation of the reactor was set to 600rpm. This agitation rate remained constant throughout the experiment. Feed gas flow to the reactor was maintained at <NUM>/min to <NUM>/min. Temperature in the bioreactor was maintained at <NUM> throughout the experiment. Na+ levels were kept at <NUM> to <NUM> ppm. Samples of gas feed into the bioreactor and off-gas from the bioreactor and fermentation broth in the bioreactor were taken at intervals, for example feed gas, off-gas and fermentation broth was sampled about daily, once two hours and once four hours respectively. Above samples were analyzed for consumption or production of various gas components, broth acetic acid concentration, and the optical density (cell density) of the culture. The unaroused volume of the reactor was maintained between <NUM> to <NUM> throughout the experiment. Also, the gas flow to the reactor was maintained at required gas flow rates using a mass flow controller. The feed syngas composition of this experiment was <NUM>% H<NUM>, <NUM>% CO<NUM> and <NUM>% N<NUM>.

A cell recycle system (CRS) was attached to the reactor before the start of the experiment. During the experiment, the rate of flow of nutrients (growth medium) to the reactor was maintained at <NUM>/min. Medium feed rate was maintained throughout the experiment. The average rate of base (NaOH) requirement to maintain pH at <NUM> was <NUM>/min, and through the CRS, <NUM>/min permeate was drawn out from the reactor.

H<NUM> and CO<NUM> in the feed gas was fixed into cell material and acetic acid. The removal of H<NUM> and CU<NUM> was calculated by comparing inlet gas composition with the effluent gas composition. Component gas uptake can be expressed in % of gas molecules converted by bacteria.

The following conversions were achieved:.

Fermentations were started as described in Example <NUM> and included the use of ethylenediamine diacetic acid (EDDA) as a chelating (complexing) agent. Chelating agents are employed to keep metals in solution as the solubility of some of the metals employed in AW indium decreases with the increasing pH. If the pH of the reactor broth is above pH <NUM>, chelating agents are employed to provide sufficient amounts of nutrients to AW. <FIG> shows a representative <NUM> hr period of the experiment that illustrates the ability to maintain cell density <NUM> while producing increasing concentrations of acetic acid <NUM>.

Fermentations were started as described in Example <NUM> and then continued to stable operation. Molybdenum was removed from culture media and then re-added to the growth medium after acetic acid productivity had dropped to <NUM>% of its starting concentration.

<FIG> illustrates acetic acid productivity <NUM> plotted against its media flow rate <NUM> with the red lines indicating the removal and re-addition of molybdenum to the growth medium. Starting at about <NUM> cumulative hours, a downward trend of HAc was observed with the molybdenum removal occurring at about <NUM> cumulative hours. This downward trend decreased, plateaued and then was reversed into an upward trend in correspondence with the re-addition of molybdenum to the media at about <NUM> hours.

<FIG> illustrates cell density <NUM> and gas flow rate (GFR) <NUM> plotted against time with the red lines indicating the removal and re-addition of molybdenum to the growth medium. Starting at about <NUM> cumulative hours, the required GFR was less compared to before the molybdenum removal occurring at about <NUM> cumulative hours. This downward trend was reversed into an upward trend in correspondence with the return of molybdenum to the media at about <NUM> hours. Required gas flow rate was determined by the CO<NUM> and H<NUM> conversions of the culture.

Synthesis or waste gas containing CO and/or CO<NUM>/H<NUM> was continuously introduced into a stirred tank bioreactor containing a strain of Clostridium ljungdahlii, along with a fermentation medium containing vitamins, trace metals and salts as described herein.

New Brunswick BioFlow <NUM> reactor containing a suitable medium was inoculated with <NUM>/l of actively growing Clostridium ljungdahlii. Before inoculation, the rate of agitation of the reactor was set to <NUM> rpm, gas flow to the reactor was adjusted to <NUM>/min and a cell recycle system was attached to the reactor. Gas and liquid samples taken from the reactor at every <NUM> to <NUM>-hour intervals were analyzed for consumption or production of various gas components, broth acetic acid concentration, broth ethanol concentration and the optical density of the culture. Also, the composition of the feed-gas was measured daily and the flow to the reactor was maintained at required gas flow rates by using a mass flow controller. Once H<NUM> conversion reached <NUM>% media flow to the reactor was started at <NUM>/min and drawn a permeate of <NUM>/min. Syngas flow to the reactor was increased based on H<NUM> conversion of the culture: gas flow was increased by <NUM>% if H<NUM> conversion is <NUM>% or above. Cell mass increased with time and reached <NUM> gil of cell mass within <NUM> hours after the inoculation of the reactor. At this point culture was producing more than <NUM>/l of ethanol. A liquid chromatograph was used to measure the broth ethanol and acetic acid concentrations. A gas chromatograph was used to measure the components of the syngas. Neutralizing agent such as NH4OH was used to maintain pH of the culture around <NUM>. Cell density of the reactor was maintained around <NUM>/L by adjusting the rate of permeate draw. Reactor was set up such that the rate of permeate draw inversely control the rate of cell purge from the reactor. Operating pressure was atmospheric.

As bacterial fermentation proceeds over a period of several hours post-inoculation, CO<NUM> is produced from the conversion of CO, and H<NUM> is consumed along with the CO. The production method and bacterial fermentation reactor system are then maintained at a steady state producing <NUM> to <NUM>/L ethanol and <NUM> to <NUM>/L acetate as products, with only occasional small adjustments to maintain acetic acid concentration in the above range and cell density at around <NUM>/L.

This method of continuous fermentation allows for the continuous production and maintenance of high ethanol concentrations with low by-product acetate concentrations under stable operating conditions to enhance use of subject bacterial on an industrial scale for ethanol production.

Fermentations with Clostridium ljungdahlii were conducted as describe in Example <NUM>.

Each trial was conducted for <NUM> hours in the presence of <NUM>/L NaCl and the following amounts of acetic acid in the reactor broth.

Addition of acetic acid to the medium had an effect on the specific productivity of ethanol. As concentrations of acetic acid increased, ethanol production also increased accordingly. There was no noticeable change in acetic acid productivity, regardless of concentration in the medium. All exogenously added acid appeared to be converted by the culture to ethanol. There was a significant increase in specific CO uptake in cultures that had exogenously added acid in the medium when compared to the control, with the highest concentration reaching the highest level of uptake at about <NUM> mmol/min/g of cells. The control averaged about <NUM> mmol/min/g of cells during this time. Acetic acid concentration also increased the hydrogen uptake. Specific productivity at steady state (g/L/day/g of cells) was as follows.

<FIG> illustrates specific gas uptake by Clostridium ljungdahlii with various concentrations of acetic acid.

A two-stage reactor was configured as shown in <FIG>. The two-stage reactor included a stirred tank bioreactor Bi <NUM> and stirred tank bioreactor Bx <NUM>. Each reactor contained a liquid medium containing vitamins, trace metals, cysteine (as sulfur source), and salts as described herein. Bioreactor Bi <NUM> was started with actively growing Clostridium ljungdahlii and Bioreactor Bx <NUM> was started with actively growing Acetobacterium woodii.

In bioreactor Bx <NUM>, <NUM> NaOH is being used as an agent to keep the pH around <NUM>. The approximate usage of NaOH per gram of cells per hour is <NUM>.

A gaseous substrate Gi <NUM> containing <NUM>% H<NUM>, <NUM>% N<NUM>, <NUM>% CO was introduced into bioreactor Bi <NUM>. A gaseous exit stream (Gp) from bioreactor Bi <NUM> was provided to bioreactor Bx <NUM> via gas stream connection <NUM>.

Water in the system was in a "closed" configuration and passed from bioreactor <NUM> to distillation <NUM> via permeate/ethanol conduit <NUM>. Water (distillation bottoms) was returned to bioreactor Bx <NUM> via water recycle line <NUM>. Acetic acid from bioreactor Bx <NUM> was sent to bioreactor Bi <NUM> via permeate acetic acid line <NUM>.

The fermentation was conducted for approximately <NUM> hours starting from water loop closure. The system was equilibrated over the first <NUM> hours and data collected over final <NUM> hrs. Influent gas streams, <NUM> (Gi) and <NUM> (Gx), and effluent gas streams <NUM> (Gp) and <NUM> (bioreactor Bx <NUM> off-gas stream) of both reactors were analyzed roughly every four hours. Analysis was performed using gas chromatography. Data was expressed as % composition. Product analysis of ethanol, acetic acid, and butanol was preformed using liquid chromatography (LC) roughly every four hours. Cell concentration of both reactors was monitored roughly every <NUM> hours.

Average % composition and gas flow rates were as follows:.

Gaseous influent feed rate into bioreactor Bi <NUM> and Bx <NUM> were maintained using mass flow controllers (MFC). Effluent gas flow rates of bioreactor Bx <NUM> and Bi <NUM> were measured using a burette. The gas flow rate to bioreactor Bx <NUM> was calculated using the ratio of N<NUM> composition of influent and effluent gas streams of bioreactor Bx <NUM>.

In this experiment only a fraction of gas leaving bioreactor Bi <NUM> was feed to bioreactor Bx <NUM>. In one instance <NUM>% of effluent gas from bioreactor Bi <NUM> was fed to bioreactor Bx <NUM>. In another instance <NUM> % of effluent gas from bioreactor Bi <NUM> was fed to bioreactor Bx <NUM>. Ethanol productivity was as follows.

Specific ethanol productivity values for two reactor system was calculated using productivity of bioreactor Bi <NUM>. Acetobacterium woodii produced zero to negligible amounts of ethanol in these experiments. Clostridium ljungdahlii specific ethanol productivity (when not combined with bioreactor <NUM>) used in this table was measured before the two reactors were connected. If <NUM>% of off gas from bioreactor Bi <NUM> is supplied to bioreactor Bx <NUM>, it is projected that specific ethanol productivity is <NUM>/L/g Clostridium cells/day.

Average carbon capture of the system was as follows.

COz is produced in bioreactor <NUM> through the water-gas shift reaction.

<FIG> shows CO <NUM> and CO<NUM> <NUM> usage in bioreactor <NUM> when coupled with bioreactor <NUM>. Conversions are calculated using molar % of effluent gas/influent gas.

A two-stage reactor was configured as shown in <FIG>. The two-stage reactor included a stirred tank bioreactor <NUM> (Bi) and stirred tank bioreactor <NUM><NUM> (Bx). Each reactor contained a liquid medium containing vitamins, trace metals, cysteine (as sulfur source), and salts as described herein. Bioreactor <NUM> (Bi) was started with actively growing of Clostridium ljungdahlii and Bioreactor <NUM> (Bx) was started with actively growing Acetobacterium woodii.

In bioreactor Bx <NUM>, <NUM> NaOH is being used as an agent to keep the pH around <NUM>. The approximate usage of NaOH per gram of cells per hour was <NUM>/min.

A gaseous substrate <NUM> (Gi) containing <NUM>% H<NUM>, <NUM>% CH<NUM>, <NUM>% CO was introduced into bioreactor Bi <NUM>. A gaseous exit stream (Gp) from bioreactor <NUM> was provided to bioreactor Bx <NUM> via gas stream connection <NUM>.

Water in the system was in a "closed" configuration and passed from bioreactor Bi <NUM> to distillation <NUM> via permeate/ethanol conduit <NUM>. Water (distillation bottoms) was returned to bioreactor Bx <NUM> via water recycle line <NUM>. Acetic acid from bioreactor Bx <NUM> was sent to bioreactor Bi <NUM> via permeate acetic acid line <NUM>.

The fermentation was conducted for approximately <NUM> hours starting from water loop closure. The system was equilibrated over the first <NUM> hours and data collected over the final <NUM> hrs. Influent gas streams, <NUM> (Gi) and <NUM> (Gx), and effluent gas streams <NUM> (Gp) and <NUM> (vent stream) of both reactors were analyzed roughly every four hours. Analysis was performed using gas chromatography. Data was expressed as % composition. Product analysis of ethanol, acetic acid, and butanol was preformed using GC roughly every four hours. Cell concentration of both reactors was monitored roughly every <NUM> hours.

Gaseous influent feed rate into bioreactor Bi <NUM> and Bx <NUM> were maintained using mass flow controllers (MFC). Effluent gas flow rates of bioreactor Bx <NUM> and Bi <NUM> were measured using a burette. The gas flow rate to the bioreactor Bx <NUM> was calculated using the ratio of CH<NUM> composition of influent and effluent gas streams of bioreactor Bx <NUM>.

In this experiment only a fraction of gas leaving bioreactor Bi <NUM> was fed to the bioreactor Bx <NUM>. Gas feed to the bioreactor Bx <NUM> was <NUM>% of total off gas from bioreactor Bi <NUM>.

Specific ethanol productivity values for two reactor system was calculated using productivity of bioreactor Bi <NUM>. Acetobacterium woodii produced zero to negligible amounts of ethanol in these experiments. Clostridium ljungdahlii specific productivity (when not combined with bioreactor Bx <NUM>) shown in this table was measured before the two reactors are connected. If <NUM>% of off gas from bioreactor Bi <NUM> is supplied to the bioreactor Bx <NUM>, it is projected that specific ethanol productivity of the system is <NUM>/L/g Clostridium cells/day.

Butyric acid is produced by Acetobacterium woodii. This experiment shows that Clostridium ljungdahlii has the ability to convert butyric acid to butanol. If <NUM>% of off gas from bioreactor Bi <NUM> is supplied to the bioreactor Bx <NUM>, it is projected that specific butanol productivity is <NUM>/L/g Clostridium cells/day.

CO<NUM> is produced in bioreactor Bi <NUM> through the water-gas shift reaction.

Claim 1:
A process comprising:
providing a gaseous substrate Gx to a bioreactor Bx, the gaseous substrate Gx comprising CO<NUM> and containing <NUM> to <NUM> mole % CO<NUM>;
providing acetogenic bacteria Mx to the bioreactor Bx, wherein the acetogenic bacteria Mx includes a sodium translocating ATPase that is active during fermentation in the bioreactor Bx;
providing sodium ions to the bioreactor Bx through one or more sodium ion sources;
fermenting the gaseous substrate Gx with the acetogenic bacteria Mx in a fermentation broth comprising the acetogenic bacteria Mx and the one or more sodium ion sources to produce one or more organic acids, wherein the fermentation broth includes less than <NUM> grams per liter yeast extract, less than <NUM> grams per liter carbohydrate, wherein the sodium ions are provided with a sodium feed rate of <NUM> to <NUM>µg/gram of cells/minute, and wherein the fermentation broth is maintained at a pH in a range of <NUM> to <NUM>;
providing at least a portion of the one or more organic acids to a bioreactor Bi;
providing a gaseous substrate Gi to the bioreactor Bi, the gaseous substrate Gi comprising CO and containing <NUM> to <NUM> mole % CO;
providing acetogenic bacteria Mi to the bioreactor Bi, wherein the acetogenic bacteria Mi includes a proton translocating ATPase that is active during fermentation in the bioreactor Bi; and
fermenting the gaseous substrate Gi in the bioreactor Bi with the acetogenic bacteria Mi in a fermentation broth comprising the acetogenic bacteria Mi to produce a liquid stream comprising one or more alcohols and a gaseous stream Gp comprising CO<NUM>.