Fermentation broth degassing

Abstract

A method of removing ammonia from a fermentation liquor that includes ammonia and carbon dioxide, where the method includes passing the fermentation liquor through a system comprising at least one pair of gas permeable membranes, wherein the at least one pair of gas permeable membranes comprises a first gas permeable membrane and a second gas permeable membrane, wherein the first gas permeable membrane is in fluid contact with air, and wherein the first gas permeable membrane removes carbon dioxide from the fermentation liquor; wherein the second gas permeable membrane is in fluid contact with an acid, and wherein the second gas permeable membrane removes ammonia from the fermentation liquor.

Description

FERMENTATION BROTH DEGASSINGCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of and priority to U.S. Provisional Patent Application No. 63 / 574,984, filed on April 5, 2024, the contents of which are incorporated herein by reference in their entirety.BACKGROUND

[0002] Steam and air stripping are traditional methods used for removing gases such as ammonia from fermentation broths. Gas-permeable membranes have been used to remove ammonia from aqueous solutions but are not typically effective with fermentation broths due to the relatively low pH of the broth. There is therefore a need for alternative methods for ammonia removal in fermentation broths.SUMMARY

[0003] The present application is directed to methods of removing ammonia from a fermentation broth (i.e., a fermentation liquor). In one aspect, a method for removing ammonia from a fermentation liquor comprising ammonia and carbon dioxide is provided, the method including passing the fermentation liquor through a system including at least one pair of gas permeable membranes, wherein the at least one pair of gas permeable membranes includes a first gas permeable membrane and a second gas permeable membrane; wherein: the first gas permeable membrane is in fluid contact with air, the first gas permeable membrane removes carbon dioxide from the fermentation liquor, the second gas permeable membrane is in fluid contact with an acid, and the second gas permeable membrane removes ammonia from the fermentation liquor. A plurality of gas permeable membranes may be added in series alternating with carbon dioxide removal (i.e., a first gas permeable membrane) and ammonia removal (i.e., a second gas permeable membrane) until the target levels of ammonia or carbon dioxide are achieved.

[0004] In the above embodiment that includes the plurality of gas permeable membranes, the system includes a plurality of the first gas permeable membranes (e.g., an early first gas permeable membrane, one or more middle first gas permeable membranes, and a latter first gas permeable membrane), each of which are in fluid contact with air, and aplurality of the second gas permeable membranes (e.g., an early second gas permeable membrane, one or more middle second gas permeable membranes, and a latter second gas permeable membrane), each of which are in fluid contact with an acid. In this configuration, the air may come into fluid contact only with the latter first gas permeable membrane and the exiting air carrying some carbon dioxide from the latter first gas permeable membrane may come in fluid contact with the one or more middle first gas permeable membranes and the early first gas permeable membrane to achieve a countercurrent configuration. Similarly, the acid may come into fluid contact only with the latter second gas permeable membrane, and the exiting acid carrying some ammonia from the latter second gas permeable membrane may come in fluid contact with the one or more middle second gas permeable membranes and the early second gas permeable membrane to achieve a countercurrent configuration.

[0005] In one aspect, a method of removing ammonia from a fermentation liquor that includes ammonia and carbon dioxide is provided. The method includes passing the fermentation liquor through a first gas permeable membrane, wherein the first gas permeable membrane is in fluid contact with air, and wherein the first gas permeable membrane removes carbon dioxide from the fermentation liquor; passing the fermentation liquor through a second gas permeable membrane, wherein the second gas permeable membrane is in fluid contact with an acid, and wherein the second gas permeable membrane removes ammonia from the fermentation liquor.

[0006] In another aspect, a method for removing ammonia from a fermentation liquor that includes ammonium and bicarbonate is provided. The method includes converting bicarbonate in the fermentation liquor to carbon dioxide, wherein the conversion of bicarbonate to carbon dioxide converts ammonium to ammonia and forms a first solution including carbon dioxide and ammonia; passing the first solution through a first gas permeable membrane, wherein the first gas permeable membrane is in fluid contact with air, and wherein the first gas permeable membrane removes the carbon dioxide from the first solution to form a second solution including ammonia; passing the second solution including ammonia through a second gas permeable membrane, wherein the second gas permeable membrane is in fluid contact with an acid, and wherein the second gas permeable membrane removes ammonia from the second solution.

[0007] In any of the above embodiments, the first gas permeable membrane and the second gas permeable membrane are connected in series.

[0008] In a further aspect, a method for removing ammonia from a fermentation liquor including ammonia and carbon dioxide is provided. The method may include passing the fermentation liquor through a gas permeable membrane, wherein the gas permeable membrane includes at least one pair of sections, wherein each pair of sections includes a first gas permeable section, a second gas permeable section, and a divider, wherein the divider separates the first gas permeable section from the second gas permeable section, and wherein flow inside the gas permeable membrane is uninterrupted; wherein the first gas permeable section is in fluid contact with air, and wherein the first gas permeable section removes carbon dioxide from the fermentation liquor; and wherein the second gas permeable section is in fluid contact with an acid, and wherein the second gas permeable section removes ammonia from the fermentation liquor.

[0009] In embodiments having the first gas permeable sections and the second gas permeable sections, air may be in fluid contact only with the first gas permeable section, and the acid may be in fluid contact with the second gas permeable section.

[0010] In embodiments having a plurality of gas permeable membranes or a gas permeable membrane having a plurality of sections, the plurality of the first gas permeable membranes includes an early first gas permeable membrane, optionally includes one or more middle first gas permeable membranes, and includes a latter first gas permeable membrane, each of which are in fluid contact with air; and the plurality of the second gas permeable membranes includes an early second gas permeable membrane, optionally includes one or more middle second gas permeable membranes, and includes a latter second gas permeable membrane, each of which are in fluid contact with an acid. In this configuration, the air may come into fluid contact only with the latter first gas permeable membrane and the exiting air carrying some carbon dioxide from the latter first gas permeable membrane may come in fluid contact with the one or more middle first gas permeable membranes and the early first gas permeable membrane to achieve a countercurrent configuration. Similarly, the acid may come into fluid contact only with the latter second gas permeable membrane, and the exiting acid carrying some ammonia from the latter second gas permeable membrane may come in fluid contact with the one or moremiddle second gas permeable membranes and the early second gas permeable membrane to achieve a countercurrent configuration. In some embodiments, the first gas permeable section and second gas permeable section in the plurality of gas permeable sections are alternating.

[0011] In any of the above embodiments, converting bicarbonate to carbon dioxide may be performed using batch evaporation.

[0012] In any of the above embodiments, the acid may be an organic acid or a mineral acid.

[0013] In any of the above embodiments, the acid may include acetic acid, propionic acid, butyric acid, citric acid, sulfuric acid, hydrochloric acid, nitric acid, or a combination of two or more thereof.

[0014] In any of the above embodiments, air that is in fluid contact with the first gas permeable membrane or section is heated before the fermentation liquor is passed through the first gas permeable membrane or section. In some embodiments, the air is heated to up to about 70 °C. In some embodiments, the relative humidity of the air is modified to be about 100%. In another embodiment, the relative humidity is modified prior to the air being heated. In yet another embodiment, the relative humidity of the air is modified using steam injection or water injection.

[0015] In any of the above embodiments, the fermentation liquor is heated before being passed through the first gas permeable membrane or section. In some embodiments, the fermentation liquor is heated to up to about 70 °C.BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG. 1 depicts an example of a system described herein, where hollow fiber membranes in series allow for removal of CO2 and ammonia. In this example, air and acid alternate as the counterfluid within the membranes.

[0017] FIG. 2 depicts another example of a system described herein, where hollow fiber membranes in series allow for removal of CO2 and ammonia by alternating air andacid as the counterfluid within the membranes, where the acid and air move countercurrently with the broth.

[0018] FIG. 3 depicts another example of a system described herein, where only one hollow fiber membrane is used and includes at least one pair of sections (such as a CCh-removal section and an ammonia-removal section) and dividers or separators dividing each section at the housing or shell side of the membrane, where the sections allow for removal of CO2 and ammonia by alternating air and acid as the counterfluid within each section of the membrane, where the acid and air move countercurrently with the broth.

[0019] FIG. 4 depicts the Liqui-Cel™ Extra-Flow membrane contactor having a central baffle on the housing or shell side as shown by Gabelman & Hwang, 1999.

[0020] FIG. 5 depicts a graph showing pH as a function of the number of times (i.e., passes or recirculation cycles) carbonated water is passed through a gas permeable membrane with an air sweep. The initial pH of the carbonated water was 5.92, and after 10 passes through the gas permeable membrane that is in fluid contact with air, the pH of the carbonated water increased to 8.10, showing successful removal of CO2.

[0021] FIG. 6 depicts pH as a function of the number of passes fermentation broth goes through a gas permeable membrane with an air sweep. The initial pH of the fermentation broth was 7.13, and after 10 passes through the gas permeable membrane that is in fluid contact with air, the pH increased to 8.34, showing successful removal of CO2.DETAILED DESCRIPTION

[0022] Various embodiments are described hereinafter. It should be noted that the specific embodiments are not intended as an exhaustive description or as a limitation to the broader aspects discussed herein. One aspect described in conjunction with a particular embodiment is not necessarily limited to that embodiment and can be practiced with any other embodiment s).

[0023] As utilized herein with respect to numerical ranges, the terms “approximately,” “about,” “substantially,” and similar terms will be understood by persons of ordinary skill in the art and will vary to some extent depending upon the context in which it is used. If there are uses of the terms that are not clear to persons of ordinary skill in theart, given the context in which it is used, the terms will be plus or minus 10% of the disclosed values. When “approximately,” “about,” “substantially,” and similar terms are applied to a structural feature (e.g., to describe its shape, size, orientation, direction, etc.), these terms are meant to cover minor variations in structure that may result from, for example, the manufacturing or assembly process and are intended to have a broad meaning in harmony with the common and accepted usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. Accordingly, these terms should be interpreted as indicating that insubstantial or inconsequential modifications or alterations of the subject matter described and claimed are considered to be within the scope of the disclosure as recited in the appended claims.

[0024] The use of the terms “a” and “an” and “the” and similar referents in the context of describing the elements (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the embodiments and does not pose a limitation on the scope of the claims unless otherwise stated. No language in the specification should be construed as indicating any non-claimed element as essential.

[0025] Fermentation broths contain ammonium and typically larger than equimolar amounts of bicarbonate leaving fermentation. When batch evaporation is performed on the fermentation broth, conversion of bicarbonate into CO2 and the subsequent removal of the CO2, releases enough basicity to convert ammonium into ammonia, which then vaporizes from the fermentation broth and leaves with the CO2 and water vapor. The relevant stoichiometry is as follows:A HCO3 aq+ H2O — > C02igas + H2O + OHaqANHiaq+ OH~qNH3 gas+ H2O

[0026] An alternative method to remove ammonia and ammonium from liquid streams is through the use of gas-permeable membranes with an ammonia-absorbing liquid on the other side of the membrane. When using gas-permeable membranes, the two liquid streams do not enter the membrane pores, but vapors released from the liquids can travel through the membrane pores. In gas-permeable membranes, such as those used in commercially available membrane contactors, the shell side and tube side refer to the two separate flow paths that facilitate gas transfer or removal. For example, in 3M Liqui-Cel™ membrane contactors, the “shell side” refers to the area where the liquid flows around the outside of the hollow fiber membrane, while “tube side” or “lumen side” refers to the area inside the hollow fibers where a vacuum, a sweep gas (e.g., air), a liquid, or an aqueous solution (e.g., an acid solution) is applied.

[0027] In an ammonia-stripping application, the pH of the ammonia-rich feed solution has to be sufficiently near or above the pKa of ammonia for significant ammonia to vaporize and pass through the membrane. If the pH is too low, the ammonia will exist as predominantly ammonium, which is not volatile. However, if bicarbonate can be simultaneously converted into CO2, this will increase the amount of hydroxyl groups in the solution to absorb protons, which helps shift the equilibrium from ammonium into ammonia.

[0028] Simultaneous air stripping has been used in the recovery of ammonia from swine manure. It was shown that air stripping enhanced ammonia removal from the manure via gas-permeable membranes. The air stripping step consisted of bubbling air through the manure while circulating the manure through a gas permeable membrane with an acid as the counter-fluid in the gas permeable membrane. However, bubbling air is an inefficient means of contacting air with a liquid to effect stripping of a dissolved component.

[0029] In the present methods, instead of using a liquid that absorbs CO2 as the counterfluid in the gas permeable membrane, air is used as the counterfluid. Without wishing to limit the present disclosure to any theory or mechanism, the membrane enhances the air to liquid contact area and enhances CO2 removal. The addition of the air-contactinggas permeable membrane for removing CO2 from the fermentation broth improves the performance of the acid-contacting gas permeable membrane for ammonia removal.

[0030] Described herein are methods that use gas-permeable membranes for removing ammonia from a fermentation broth (i.e., a fermentation liquor) that includes ammonia and carbon dioxide. In an embodiment, the method includes passing the fermentation liquor through a system including a gas permeable membrane that is in fluid contact with air and a gas permeable membrane that is in fluid contact with an acid. The gas permeable membrane that is in fluid contact with air removes carbon dioxide from the fermentation liquor, and the gas permeable membrane that is in fluid contact with an acid removes ammonia from the fermentation liquor.

[0031] In another embodiment, the method includes: passing the fermentation liquor through a system including at least one pair of gas permeable membranes, wherein the at least one pair of gas permeable membranes includes a first gas permeable membrane and a second gas permeable membrane; wherein the first gas permeable membrane is in fluid contact with air, and wherein the first gas permeable membrane removes carbon dioxide from the fermentation liquor; and wherein the second gas permeable membrane is in fluid contact with an acid, and wherein the second gas permeable membrane removes ammonia from the fermentation liquor.

[0032] In another embodiment, the method includes: passing the fermentation liquor through a first gas permeable membrane, wherein the first gas permeable membrane is in fluid contact with air, and wherein the first gas permeable membrane removes carbon dioxide from the fermentation liquor; and passing the fermentation liquor through a second gas permeable membrane, wherein the second gas permeable membrane is in fluid contact with an acid, and wherein the second gas permeable membrane removes ammonia from the fermentation liquor.

[0033] In yet another embodiment, the method includes: converting bicarbonate in the fermentation liquor to carbon dioxide, wherein the conversion of bicarbonate to carbon dioxide converts ammonium to ammonia, and wherein the conversion forms a solution including carbon dioxide and ammonia; passing the solution including carbon dioxide and ammonia through a first gas permeable membrane, wherein the first gas permeable membrane is in fluid contact with air, and wherein the first gas permeable membraneremoves carbon dioxide to form a solution including ammonia; passing the solution including ammonia through a second gas permeable membrane, wherein the second gas permeable membrane is in fluid contact with an acid, and wherein the second gas permeable membrane removes ammonia from the solution.

[0034] In any of the embodiments described herein, the first gas permeable membrane and the second gas permeable membrane are connected in series. In the first gas permeable membrane, air is used to strip CO2 from the fermentation broth, which raises the pH of the fermentation broth. The fermentation broth then passes through a second membrane, in which an acid absorbs NH3 released from the fermentation broth. In some embodiments, the system includes at least two sets including the first gas permeable membrane and the second gas permeable membrane. In some embodiments, the system includes a plurality of sets, each set including a first gas permeable membrane (e.g., an early first gas permeable membrane, optionally one or more middle first gas permeable membranes, and a latter first gas permeable membrane), and a second gas permeable membrane (e.g., an early second gas permeable membrane, optionally one or more middle second gas permeable membranes, and a latter second gas permeable membrane). In any of the embodiments described herein, the first gas permeable membrane removes bicarbonate from the fermentation broth and is designated as the “air membrane”. In any of the embodiments described herein, the second gas permeable membrane removes ammonia from the fermentation broth and is designated as the “acid membrane”.

[0035] In any of the embodiments described herein, the gas permeable membranes may be fitted with baffles on the housing or shell-side to minimize bypassing and to provide a component of velocity normal to the fibers (Gabelman & Hwang, 1999).

[0036] As a non-limiting example of the at least two sets of gas permeable membranes or the plurality of sets, the gas permeable membranes are connected in series such that the fermentation passes through a first air membrane, then through a first acid membrane, then through a second air membrane, then through a second acid membrane, and is repeatedly passed through an air membrane and then through an acid membrane until a target level of ammonia of less than about 10 ppm in the fermentation broth is reached. In some embodiments, the target level of ammonia in the fermentation broth is less than about 10 ppm, less than about 9 ppm, less than about 8 ppm, less than about 7 ppm, less thanabout 6 ppm, less than about 5 ppm, less than about 4 ppm, less than about 3 ppm, less than about 2 ppm, or less than about 1 ppm. The levels of ammonia and / or carbon dioxide in the fermentation broth may be measured using any method known to those skilled in the art.

[0037] In yet another embodiment, the method includes passing the fermentation broth through a system including one partitioned, or divided, single gas permeable membrane. The divided single gas permeable membrane includes at least one pair of sections, wherein each pair of sections includes a first gas permeable section, a second gas permeable section, and a divider or separator, where the divider or separator separates the first gas permeable section from the second gas permeable section. In some embodiments, the dividers or separators are similar to the baffles as described in Gabelman & Hwang, 1999, but extends the full housing or shell side, and are used to separate and isolate, at the shell side, each section of the gas permeable membrane system where the air or the acid would flow. The interior of the gas permeable membrane remains one system for the fermentation broth to flow through. The sections are similar to individual membranes aligned in series. In this configuration, the first gas permeable section is in fluid contact with air and removes carbon dioxide from the fermentation broth; and the second gas permeable section is in fluid contact with an acid and removes ammonia from the fermentation liquor.

[0038] FIG. 1 depicts an example of a system for removing ammonia from a fermentation broth (100). The system illustrates hollow-fiber membranes, but any suitable gas permeable membranes may be used in this system. The system includes a CCh-removal hollow-fiber membrane (101) and an ammonia-removal hollow-fiber membrane (105), and may further include additional CCh-removal hollow-fiber membranes (109) and ammonia- removal hollow-fiber membranes (113). The CCh-removal hollow-fiber membranes (101, 109) each include an inlet to provide air (102, 110) as a counterfluid to the CCh-removal hollow-fiber membrane (101, 109), where the air (102, 110) strips CCh from the fermentation broth, and both the air and CCh (103, 111) leave through an outlet. Similarly, the ammonia-removal hollow-fiber membranes (105, 113) each include an inlet to provide an acid (106, 114) as a counterfluid to the ammonia-removal hollow-fiber membrane (105, 113), where the acid strips ammonia from the fermentation broth, and both the acid and ammonia (107, 115) leave through an outlet. In FIG. 1, the CCh-removal hollow-fiber membranes (101, 109) and ammonia-removal hollow-fiber membranes (105, 113) areconnected in series, where the CCh-removal hollow-fiber membranes (101, 109) and ammonia-removal hollow-fiber membranes (105, 113) are alternated, thus the air and the acid counterfluids are alternating.

[0039] In the system of FIG. 1, a fermentation broth (100) enters a CCh-removal hollow-fiber membrane (101), where the air counterfluid (102) strips CO2 from the fermentation broth, resulting in a fermentation broth having a reduced amount of CO2 (104) leaving the CCh-removal hollow-fiber membrane (101). The fermentation broth having a reduced amount of CO2 (104) enters the ammonia-removal hollow-fiber membrane (105), where the acid counterfluid (106) strips ammonia from the fermentation broth, resulting in a fermentation broth having a reduced amount of ammonia (108) leaving the ammonia- removal hollow-fiber membrane (105). This process may be repeated if a sufficient amount of CO2 and ammonia is not removed from the fermentation broth. Briefly, the fermentation broth having a reduced amount of ammonia (108) enters a second CCh-removal hollowfiber membrane (109), where the air counterfluid (110) strips CO2 from the fermentation broth, resulting in a CCh-lean fermentation broth (112) leaving the CCh-removal hollowfiber membrane (109). The CCh-lean fermentation broth (112) enters the second ammonia- removal hollow-fiber membrane (113), where the acid counterfluid (114) strips ammonia from the fermentation broth, resulting in a CO2- and ammonia-lean fermentation broth (116) leaving the ammonia-removal hollow-fiber membrane (113).

[0040] FIG. 2 depicts another example of a system for removing ammonia from a fermentation broth entering the system (200). The system illustrates hollow-fiber membranes, but any suitable gas permeable membranes may be used in this system. The system includes a CCh-removal hollow-fiber membrane (201) and an ammonia-removal hollow-fiber membrane (203) and may further include additional CCh-removal hollow-fiber membranes (205) and ammonia-removal hollow-fiber membranes (207). The CCh-removal hollow-fiber membrane (205) includes an inlet to provide air (212) as a counterfluid to the CCh-removal hollow-fiber membrane (205), where the air (212) strips CO2 from the fermentation broth and then both the air and CO2 leave through an outlet (213). The CCh- removal hollow-fiber membrane (201) includes an inlet to provide the air and CO2 (213) exiting the CCh-removal hollow-fiber membrane (205) as a counterfluid to the CCh-removal hollow-fiber membrane (201), where the air in the mix (213) strips CO2 from the fermentation broth and then both the air and CO2 leave through an outlet (214). Similarly,the ammonia-removal hollow-fiber membrane 207 includes an inlet to provide an acid (209) as a counterfluid to the ammonia-removal hollow-fiber membrane (207), where the acid(209) strips ammonia from the fermentation broth, and then both the acid and ammonia(210) leave through an outlet. The ammonia-removal hollow-fiber membrane (203) includes an inlet to provide an acid and ammonia (210) exiting ammonia-removal hollowfiber membrane (207) as a counterfluid to the ammonia-removal hollow-fiber membrane (203), where the acid in the mix (210) strips ammonia from the fermentation broth, and then both the acid and ammonia (211) leave through an outlet. In FIG. 2, the CCh-removal hollow-fiber membranes (201, 205) and ammonia-removal hollow-fiber membranes (203, 207) are connected in series, where the CCh-removal hollow-fiber membranes (201, 205) and ammonia-removal hollow-fiber membranes (203, 207) are alternated, thus the air and the acid counterfluids are alternating. There is a single source providing the air (212) and acid (209), thus an efficient countercurrent configuration is achieved where fresh air (212) contacts a more CCh-lean broth (204) in CCh-removal hollow-fiber membrane (205), and the captured CO2 and air (213) contacts a less CCh-lean broth (200) in CCh-removal hollowfiber membrane (201). Similarly, fresh acid (209) contacts a more ammonia-lean broth (206) in ammonia-removal hollow-fiber membrane (207), and the captured ammonia and acid (210) contacts a less ammonia-lean broth (202) in ammonia-removal hollow-fiber membrane (203). The countercurrent effect saves on the amount of air or acid that is necessary to be fed in inlets (212 and 209), respectively to achieve the target level of CO2 and ammonia in the final CO2- and ammonia-lean broth (208) and results in a more CO2 concentrated air stream (214) and a more ammonia concentrated acid stream (211) exiting the system.

[0041] Without being limiting, the countercurrent configuration is optional for either 1) the CCh-removal air stream (212), or 2) the ammonia-removal acid stream (209). In the case of 1), fresh air is fed in parallel as counterfluid to the CCh-removal hollow-fiber membranes (201, 205), while fresh acid is fed countercurrently in series as a counterfluid through the inlet (209) of the ammonia-removal hollow-fiber membrane (207), and where it exits through the outlet of the ammonia-removal hollow-fiber membrane (207) carrying some removed ammonia (210) and enters through the inlet of ammonia-removal hollowfiber membrane (203) to strip more ammonia before exiting through the outlet of ammonia- removal hollow-fiber membrane (203) carrying all the removed ammonia (211). In the caseof 2), fresh acid is fed in parallel as a counterfluid to the ammonia-removal hollow-fiber membranes (203, 207), while fresh air is fed countercurrently in series as a counterfluid through the inlet (212) of the CCh-removal hollow-fiber membrane (205) and exits through the outlet of the CCh-removal hollow-fiber membrane (205) carrying some removed CO2 (213), where it then enters through the inlet of CCh-removal hollow-fiber membrane (201) to strip more CO2 before exiting through the outlet of CCh-removal hollow-fiber membrane (201) carrying all the removed CO2 (214).

[0042] In the system of FIG. 2, a fermentation broth (200) enters a CCh-removal hollow-fiber membrane (201), where the air present in the air / CCh mix counterfluid (213) strips CO2 from the fermentation broth (200), resulting in a fermentation broth having a reduced amount of CO2 (202) leaving the CCh-removal hollow-fiber membrane (201). The fermentation broth having a reduced amount of CO2 (202) enters the ammonia-removal hollow-fiber membrane (203), where the acid in the acid / ammonia mix counterfluid (210) strips ammonia from the fermentation broth, resulting in a fermentation broth having a reduced amount of ammonia (204) leaving the ammonia-removal hollow-fiber membrane (203). The fermentation broth having a reduced amount of ammonia (204) enters a second CCh-removal hollow-fiber membrane (205), where the air counterfluid (212) strips CO2 from the fermentation broth. This results in a C Ch-lean fermentation broth (206) leaving the CCh-removal hollow-fiber membrane (205). The CCh-lean fermentation broth (206) enters the second ammonia-removal hollow-fiber membrane (207), where the acid counterfluid (209) strips ammonia from the fermentation broth. This results in a CO2- and ammonia-lean fermentation broth (208), leaving the ammonia-removal hollow-fiber membrane (207). This process may be repeated if the targeted removal of CO2 and / or ammonia from the fermentation broth is not achieved by adding more CCh-removal and ammonia-removal hollow-fiber membranes in the same alternating fashion and by feeding the air or the acid counterfluids in a countercurrent configuration to the CCh-removal hollow-fiber membranes and the ammonia-removal hollow-fiber membranes, respectively.

[0043] FIG. 3 depicts another example of a system for removing ammonia from a fermentation broth (300) entering the system. The system illustrates a hollow-fiber membrane, but any suitable gas permeable membrane may be used in the system. The system includes a hollow-fiber membrane (301), partitioned or separated by at least one or more dividers or separators (302a, 302b, and 302c), which expands the full housing or shellside to isolate each partition or section (301a, 301b, 301c, and 301d). The sections are similar to the individual membranes described above for FIG.1 and FIG. 2. The system of FIG. 3 includes a CCh-removal section (301a) and an ammonia-removal section (301b) and may further include additional CCh-removal sections (301c) and ammonia-removal sections (301d). The CCh-removal section (301c) includes an inlet to provide air (312) as a counterfluid to the CCh-removal section (301c), where the air (312) strips CCh from the fermentation broth and then both the air and CCh leave through an outlet (213). The CCh- removal section (301a) includes an inlet to provide air and CCh (313) exiting membrane section (301c) as a counterfluid to the CCh-removal section (301a), where the air in the mix (313) strips CCh from the fermentation broth and then both the air and CCh leave through an outlet (314). Similarly, the ammonia-removal section (301d) includes an inlet to provide an acid (309) as a counterfluid to the ammonia-removal section (3 Old), where the acid (309) strips ammonia from the fermentation broth, and then both the acid and ammonia (310) leave through an outlet. The ammonia-removal section (301b) includes an inlet to provide an acid and ammonia (310) exiting membrane section (3 Old) as a counterfluid to the ammonia-removal section (301b), where the acid in the mix (310) strips ammonia from the fermentation broth, and then both the acid and ammonia (311) leave through an outlet. In FIG. 3, the CCh-removal sections (301a, 301c) and ammonia-removal sections (301b, 301d) are part of the same membrane, separated by dividers (302a, 302b, 302c), where the CCh- removal sections (301a, 301c) and ammonia-removal sections (301b, 301d) are alternated, thus the air and the acid counterfluids are alternating. There is a single source providing the air (312) and acid (309), thus an efficient countercurrent configuration is achieved where fresh air (312) contacts a more CCh-lean broth in CCh-removal section (301c), and the captured CCh and air (313) contacts a less CCh-lean broth in CCh-removal section (301a). Similarly, fresh acid (309) contacts a more ammonia-lean broth in ammonia-removal section (301d), and the captured ammonia and acid (310) contacts a less ammonia-lean broth in ammonia-removal section (301b). The countercurrent effect saves on the amount of air or acid that is necessary to be fed in inlets (312) and (309), respectively to achieve the target level of CCh and ammonia in the final CCh- and ammonia-lean broth (308) and it results in a more CCh concentrated air stream (314) and a more ammonia concentrated acid stream (311) exiting the system.

[0044] Without being limiting, the countercurrent configuration is optional for either 1) the CCh-removal air stream (312) or for 2) the ammonia-removal acid stream (309). In the case of 1), fresh air is fed in parallel as a counterfluid to the CCh-removal sections (301a, 301c), while fresh acid is fed countercurrently in series as a counterfluid through the inlet (309) of the ammonia-removal section (3 Old) and exits through the outlet of the ammonia-removal section (301d) carrying some removed ammonia (310) and enters through the inlet of ammonia-removal hollow-fiber membrane (301b) to strip more ammonia before exiting through the outlet of ammonia-removal hollow-fiber membrane (301b) carrying all the removed ammonia (311). In the case of 2), fresh acid is fed in parallel as counterfluid to the ammonia-removal sections (301b, 301d), while fresh air is fed countercurrently in series as a counterfluid through the inlet (312) of the CCh-removal section (301c) and exits through the outlet of the CCh-removal section (301c) carrying some removed CO2 (313) and enters through the inlet of CCh-removal section (301a) to strip more CO2 before exiting through the outlet of CCh-removal section (301a) carrying all the removed CO2 (314).

[0045] In the system of FIG. 3, a fermentation broth (300) enters a hollow-fiber membrane (301) divided or partition into isolated sections at the housing or shell side. The broth (300) first enters the CCh-removal section (301a), where the air present in the air / CCh mix counterfluid (313) strips CO2 from the fermentation broth (300), resulting in a fermentation broth having a reduced amount of CO2 leaving the CCh-removal section (301a). The fermentation broth having a reduced amount of CO2 flows into the ammonia- removal section (301b), where the acid in the acid / ammonia mix counterfluid (310) strips ammonia from the fermentation broth, resulting in a fermentation broth having a reduced amount of ammonia leaving the ammonia-removal section (301b). The fermentation broth having a reduced amount of ammonia enters a second CCh-removal section (301c), where the air counterfluid (312) strips CO2 from the fermentation broth, resulting in a CCh-lean fermentation broth leaving the CCh-removal section (301c). The CCh-lean fermentation broth then flows into the second ammonia-removal section (3 Old), where the acid counterfluid (309) strips ammonia from the fermentation broth, resulting in a CO2- and ammonia-lean fermentation broth (308), leaving the ammonia-removal section (301d). This process may be repeated if the targeted removal of CO2 and / or ammonia from the fermentation broth in not achieved by adding more CCh-removal and ammonia-removalsections in the same alternating fashion and by feeding the air or the acid counterfluids in a countercurrent configuration to the CCh-removal sections and the ammonia-removal sections, respectively.

[0046] In some embodiments, the conversion of bicarbonate to carbon dioxide is performed using batch evaporation.

[0047] In some embodiments, the acid is an organic acid. Non-limiting examples of the organic acid include acetic acid, propionic acid, butyric acid, citric acid, or a combination thereof. In yet other embodiments, the acid is a mineral acid. Non-limiting examples of the mineral acid include sulfuric acid, hydrochloric acid, nitric acid, or a combination thereof.

[0048] In some embodiments, air that is in fluid contact with the first gas permeable membrane is heated before the fermentation liquor is passed through the system. In some embodiments, the air is heated to up to about 70 °C. In some embodiments, the relative humidity of the air is modified to be from low ambient humidity of less than about 10% to about 100% prior to the air being heated. In some embodiments, the relative humidity of the air is modified through steam injection or water injection. In some embodiments, when the relative humidity of the air is modified using water injection, the amount of water added is adjusted such that when the stream is heated, the water vaporizes. In other embodiments, when the relative humidity of the air is modified using water injection, the addition of water occurs simultaneously as the air is being heated. In some embodiments, the fermentation liquor is heated before being passed through the system. In some embodiments, the fermentation liquor is heated to up to about 70 °C.

[0049] In another aspect, a method of removing ammonia from a fermentation liquor including ammonia is provided, the method including: passing the fermentation liquor through a gas permeable membrane, wherein the gas permeable membrane is in fluid contact with air on one side, and an acid on the other side, wherein the gas permeable membrane removes ammonia from the fermentation liquor.

[0050] FIG. 4 shows a drawing of a hollow-fiber membrane module by Liqui-Cel™ (Gabelman & Hwang, 1999). This module shows a central shell baffle, which improved efficiency by minimizing shell-side bypassing and by providing a component of velocitynormal to the membrane surface. A similar design to the baffle installed on the shell side only can also be used to provide isolated partitions or sections in the shell side as proposed in FIG. 3.

[0051] The present invention, thus generally described, will be understood more readily by reference to the following examples, which are provided by way of illustration and are not intended to be limiting of the present invention.EXAMPLES

[0052] Example 1. Ammonia removal using a single gas-permeable membrane. A fermentation broth in a 55-gallon drum was passed through a 2.5x8 Liqui-Cel™ unit for ammonia removal for a period of 5 hours in batch mode, and ammonia was removed using a diluted sulfuric acid solution. The fermentation broth had a yellowish color and a viscosity slightly higher than water. Results from the ammonia removal test are summarized in Table 1 below. Use of a single gas permeable membrane did not show complete ammonia removal.Table 1. Results of the ammonia removal test using a single gas permeable membrane.*Note: pH variation from 2-6

[0053] Before and after the ammonia removal test, the Liqui-Cel™ unit was subjected to a quality control (QC) water degasification test (Tables 2 and 3). This preliminary performance test used DI water and measured the oxygen removal efficiency at a specific water flow rate and temperature. The QC water degasification test allows for measurement of any membrane fouling produced by unknown chemicals in the wastewater sample during the ammonia removal test.Table 2. Results of the membrane QC test before the ammonia removal test.Table 3. Results of the membrane QC test after the ammonia removal test.

[0054] The QC water degasification test results show an average of 84% oxygen removal before and after the Ammonia Removal Test. The pressure drop difference measured across the membrane unit can be explained by the pressure gauges’ inherent inaccuracy, and thus it is concluded that particle fouling was not an issue.

[0055] Example 2. CO2 removal from carbonated water using a permeable membrane with an air sweep. A 3M Liqui-Cel™ EXF 2.5x8 membrane (G453 2.5x8 CN, Cartridge AH009022) was used to test the removal of carbon dioxide from solutions (e.g., carbonated water) using air as the sweep gas. In this example, air was passed through the tube side while the liquid recirculated in the shell side. The liquid side (the shell-side) was fully enclosed, while on the tube side, the air was simply vented after passing through the system.

[0056] The first test flowed carbonated water on the shell side at 2 gallons per minute (GPM) flow, with a flow of air as a sweep gas on the tube side at 20 standard cubic foot per hour (SCFH). Up to 10 passes or recirculation cycles of the liquid were performed. Initial pH of the carbonated water was 5.92. The temperature of the system was 22°C. After 10 passes, the pH increased to 8.10, showing successful removal of CO2. FIG. 5 shows the as a function of the number of passes and shows that the pH increased as the number of passes increased.

[0057] Example s. CO2 removal from fermentation broth using a permeable membrane with an air sweep. The same 3M Liqui-Cel™ EXF 2.5x8 membrane (G453 2.5x8 CN, Cartridge AH009022) was used to repeat the experiment in Example 2 but used fermentation broth. The fermentation broth was acquired from the mixed-culture fermentation of dextrose and corn steep liquor for producing volatile fatty acids (e.g., acetic, propionic, butyric acids). pH was maintained in the fermentation near neutrality by adding sodium and potassium hydroxide as the acids are formed and the temperature of the fermentation was kept at 40°C. The fermentation produced CO2 and ammonia as well, which remains in the broth. The flow of the broth on the shell side was 2 GPM, and the air flow in the tube side was 20 SCFH to act as a sweep gas. The initial pH of the broth was 7.13. The temperature of the system was on average 24°C ± 1. After 10 passes or recirculation cycles, the pH increased to 8.34, showing successful removal of CO2. FIG. 6 shows the pH as a function of the number of passes and shows that pH increased as the number of passes increased. It should be noted that, as mentioned, the broth exits the fermentation at 40°C, however, that temperature was not maintained while this test was performed, which ran at 24°C ± 1. However, in an industrial process, the 40°C temperature may be maintained and with such higher temperature, CO2 removal should be more efficient.

[0058] While certain embodiments have been illustrated and described, it should be understood that changes and modifications can be made therein in accordance with ordinary skill in the art without departing from the technology in its broader aspects as defined in the following claims.

[0059] The embodiments, illustratively described herein may suitably be practiced in the absence of any element or elements, limitation or limitations, not specifically disclosed herein. Thus, for example, the terms “comprising,” “including,” “containing,” etc. shall be read expansively and without limitation. Additionally, the terms and expressions employed herein have been used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the claimed technology. Additionally, the phrase “consisting essentially of’ will be understood to include those elements specifically recited and those additional elements that do not materially affect thebasic and novel characteristics of the claimed technology. The phrase “consisting of’ excludes any element not specified.

[0060] The present disclosure is not to be limited in terms of the particular embodiments described in this application. Many modifications and variations can be made without departing from its spirit and scope, as will be apparent to those skilled in the art. Functionally equivalent methods and compositions within the scope of the disclosure, in addition to those enumerated herein, will be apparent to those skilled in the art from the foregoing descriptions. Such modifications and variations are intended to fall within the scope of the appended claims. The present disclosure is to be limited only by the terms of the appended claims, along with the full scope of equivalents to which such claims are entitled. It is to be understood that this disclosure is not limited to particular methods, reagents, compounds, compositions, or biological systems, which can of course vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting.

[0061] In addition, where features or aspects of the disclosure are described in terms of Markush groups, those skilled in the art will recognize that the disclosure is also thereby described in terms of any individual member or subgroup of members of the Markush group.

[0062] As will be understood by one skilled in the art, for any and all purposes, particularly in terms of providing a written description, all ranges disclosed herein also encompass any and all possible subranges and combinations of subranges thereof. Any listed range can be easily recognized as sufficiently describing and enabling the same range being broken down into at least equal halves, thirds, quarters, fifths, tenths, etc. As a nonlimiting example, each range discussed herein can be readily broken down into a lower third, middle third and upper third, etc. As will also be understood by one skilled in the art all language such as “up to,” “at least,” “greater than,” “less than,” and the like, include the number recited and refer to ranges which can be subsequently broken down into subranges as discussed above. Finally, as will be understood by one skilled in the art, a range includes each individual member.

[0063] All publications, patent applications, issued patents, and other documents referred to in this specification are herein incorporated by reference as if each individualpublication, patent application, issued patent, or other document was specifically and individually indicated to be incorporated by reference in its entirety. Definitions that are contained in text incorporated by reference are excluded to the extent that they contradict definitions in this disclosure.

[0064] Other embodiments are set forth in the following claims.

Claims

WHAT IS CLAIMED IS:

1. A method for removing ammonia from a fermentation liquor comprising ammonia and carbon dioxide, the method comprising: passing the fermentation liquor through a system comprising at least one pair of gas permeable membranes, wherein the at least one pair of gas permeable membranes comprises a first gas permeable membrane and a second gas permeable membrane, wherein: the first gas permeable membrane is in fluid contact with air; the first gas permeable membrane removes carbon dioxide from the fermentation liquor; the second gas permeable membrane is in fluid contact with an acid; and the second gas permeable membrane removes ammonia from the fermentation liquor.

2. The method of claim 1, wherein the first gas permeable membrane and the second gas permeable membrane are connected in series.

3. The method of claim 1 or 2, wherein the acid is an organic acid or a mineral acid.

4. The method of any one of claims 1-3, wherein the acid comprises acetic acid, propionic acid, butyric acid, citric acid, sulfuric acid, hydrochloric acid, nitric acid, or a combination thereof.

5. The method of any one of claims 1-4, wherein the system comprises a plurality of gas permeable membranes connected in series.

6. The method of claim 5, wherein each first gas permeable membrane and second gas permeable membrane in the plurality of gas permeable membranes are alternating, thereby removing carbon dioxide and ammonia until a target level of ammonia or carbon dioxide is achieved.

7. The method of claim 6, wherein the target level of ammonia is 10 ppm or less.

8. The method of any one of claims 5-7, wherein the air is in fluid contact only with the first gas permeable membrane, and the acid is in fluid contact only with the second gas permeable membrane.

9. The method of any one of claims 5-8, wherein exiting air carrying carbon dioxide from the latter first gas permeable membranes come in fluid contact with early first gas permeable membranes to achieve a countercurrent configuration.

10. The method of any one of claims 5-9, wherein exiting acid carrying ammonia from the latter second gas permeable membranes come in fluid contact with early second gas permeable membranes to achieve a countercurrent configuration.

11. A method for removing ammonia from a fermentation liquor comprising ammonia and carbon dioxide, the method comprising: passing the fermentation liquor through a first gas permeable membrane, wherein the first gas permeable membrane is in fluid contact with air, and wherein the first gas permeable membrane removes carbon dioxide from the fermentation liquor; passing the fermentation liquor through a second gas permeable membrane, wherein the second gas permeable membrane is in fluid contact with an acid, and wherein the second gas permeable membrane removes ammonia from the fermentation liquor.

12. The method of claim 11, wherein the first gas permeable membrane and the second gas permeable membrane are connected in series.

13. The method of claim 11 or 12, wherein the acid is an organic acid or a mineral acid.

14. The method of any of claims 11-13, wherein the acid comprises acetic acid, propionic acid, butyric acid, citric acid, sulfuric acid, hydrochloric acid, nitric acid, or a combination thereof.

15. A method for removing ammonia from a fermentation liquor comprising ammonium and bicarbonate, the method comprising: converting bicarbonate in the fermentation liquor to carbon dioxide, wherein the conversion of bicarbonate to carbon dioxide converts ammonium to ammonia and forms a first solution comprising carbon dioxide and ammonia; passing the first solution through a first gas permeable membrane, wherein the first gas permeable membrane is in fluid contact with air, and wherein the first gas permeable membrane removes the carbon dioxide to form a second solution comprising ammonia; passing the second solution through a second gas permeable membrane, wherein the second gas permeable membrane is in fluid contact with an acid, and wherein the second gas permeable membrane removes the ammonia from the second solution.

16. The method of claim 15, wherein converting bicarbonate to carbon dioxide is performed using batch evaporation.

17. The method of claim 15 or claim 16, wherein the first gas permeable membrane and the second gas permeable membrane are connected in series.

18. The method of any of claims 15-17, wherein the acid is an organic acid or a mineral acid.

19. The method of any of claims 15-18, wherein the acid comprises acetic acid, propionic acid, butyric acid, citric acid, sulfuric acid, hydrochloric acid, nitric acid, or a combination thereof.

20. The method of any one of the preceding claims, wherein air that is in fluid contact with the first gas permeable membrane is heated before the first solution is passed through the first gas permeable membrane.

21. The method of claim 20, wherein the air is heated to up to about 70 °C.

22. The method of claim 20 or 21, wherein the relative humidity of the air is modified to be about 100%.

23. The method of claim 22, wherein the relative humidity is modified prior to the air being heated.

24. The method of claim 22 or 23, wherein the relative humidity of the air is modified using steam injection or water injection.

25. The method of any one of the preceding claims, wherein the fermentation liquor is heated before being passed through the first gas permeable membrane.

26. The method of claim 25, wherein the fermentation liquor is heated to up to about 70 °C.

27. A method for removing ammonia from a fermentation liquor comprising ammonia and carbon dioxide, the method comprising: passing the fermentation liquor through a gas permeable membrane, wherein the gas permeable membrane comprises: at least one pair of sections, wherein each pair of sections comprises a first gas permeable section, a second gas permeable section, and a divider, wherein the divider separates the first gas permeable section from the second gas permeable section, and wherein flow inside the gas permeable membrane is uninterrupted; wherein the first gas permeable section is in fluid contact with air, and wherein the first gas permeable section removes carbon dioxide from the fermentation liquor; and wherein the second gas permeable section is in fluid contact with an acid, and wherein the second gas permeable section removes ammonia from the fermentation liquor.

28. The method of claim 27, wherein the first gas permeable section and the second gas permeable section are connected in series.

29. The method of claim 27 or 28, wherein the acid is an organic acid or a mineral acid.

30. The method of any of claims 27-29, wherein the acid comprises acetic acid, propionic acid, butyric acid, citric acid, sulfuric acid, hydrochloric acid, nitric acid, or a combination thereof.

31. The method of any one of claims 27-30, wherein the method comprises passing the fermentation liquor through a plurality of gas permeable sections connected in series.

32. The method of claim 31, wherein the first gas permeable section and second gas permeable section in the plurality of gas permeable sections are alternating, thereby removing carbon dioxide and ammonia until a target level of ammonia or carbon dioxide is achieved.

33. The method of claim 32, wherein the target level of ammonia is 10 ppm or less.

34. The method of any one of claims 31-33, wherein the air is in fluid contact only with the first gas permeable section, and the acid is in fluid contact only with the second gas permeable section.

35. The method of any one of claims 31-34, wherein the plurality of gas permeable sections comprises a plurality of first gas permeable sections comprising an early first gas permeable section, optionally one or more middle first gas permeable sections, and a latter first gas permeable section; and a plurality of second gas permeable sections comprising an early second gas permeable section, optionally one or more middle second gas permeable sections, and a latter second gas permeable section, wherein exiting air carrying carbon dioxide from the latter first gas permeable section comes in fluid contact with the one or more middle first gas permeable membranes and the early first gas permeable sections to achieve a countercurrent configuration, and exiting acid carrying ammonia from the latter second gas permeable section comes in fluid contact with the one or more middle second gas permeable membranes and the early second gas permeable section to achieve a countercurrent configuration.

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