Notice of Pre-AIA or AIA Status
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA .
DETAILED ACTION
The instant application is a U.S. National Phase of PCT/EP2019/079433 filed on 10/28/2019, with foreign priority application DE10 2018 126 953.6, filed October 29, 2018. Applicant’s amendment filed January 14, 2026 is acknowledged. Claims 11 and 15 are canceled, and claim 1 is amended. Currently claims 1-10 and 12-14 are pending, wherein claim 14 is withdrawn.
Claim Rejections - 35 USC § 103
The following is a quotation of 35 U.S.C. 103 which forms the basis for all obviousness rejections set forth in this Office action:
A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made.
The factual inquiries for establishing a background for determining obviousness under 35 U.S.C. 103 are summarized as follows:
1. Determining the scope and contents of the prior art.
2. Ascertaining the differences between the prior art and the claims at issue.
3. Resolving the level of ordinary skill in the pertinent art.
4. Considering objective evidence present in the application indicating obviousness or nonobviousness.
This application currently names joint inventors. In considering patentability of the claims the examiner presumes that the subject matter of the various claims was commonly owned as of the effective filing date of the claimed invention(s) absent any evidence to the contrary. Applicant is advised of the obligation under 37 CFR 1.56 to point out the inventor and effective filing dates of each claim that was not commonly owned as of the effective filing date of the later invention in order for the examiner to consider the applicability of 35 U.S.C. 102(b)(2)(C) for any potential 35 U.S.C. 102(a)(2) prior art against the later invention.
Claims 1-10 and 12-13 remain rejected under 35 U.S.C. 103 as being unpatentable over Krajete (WO 2012110256 A1, cited in PTO-892 mailed 3/5/2024, hereinafter “Krajete”) in view of Yan et al. (Bioresource Technology 259 (2018) 67–74, cited in PTO-892 mailed 10/29/2025, hereinafter “Yan”), as evidenced by Awe et al. (Waste Biomass Valor (2017) 8:267–283, cited in PTO-892 mailed 7/3/2024, hereinafter “Awe”) and DSMZ-German Collection of Microorganisms (Media 119, 2022, pgs. 1-2, cited in PTO-892 filed 3/5/2024).
Regarding claims 1, 5 and 12, Krajete teaches a method of converting carbon dioxide and hydrogen to methane by methanogenic microorganisms (abstract). The method consists of contacting the methanogenic microorganisms with in-gas comprising carbon dioxide and hydrogen sulfide in a reaction vessel (abstract, pg. 30, line 14). The method includes a continuous mode of cultivation, where the methanogenic bacteria are continuously supplied with fresh medium and other gases, such as hydrogen and carbon dioxide (pg. 45, lines 24-28). Further, the in-flow of gases for cell growth were set to a partial pressure ratio of carbon dioxide to hydrogen to be maintained from a range of 1:0.5 to 1:5 (parts carbon dioxide: parts hydrogen), well within the instant range 1:0.6-1:5 CO2:H2 which anticipates claim 1 (pg. 58, line 22). Krajete teaches both gases are generally fed into the reaction vessel of the invention according to the desired ratio of their partial pressures and may be pure or contaminated with other gases tolerated by the system (pg. 41, lines 6-10). Krajete teaches the carbon dioxide used in the method may be pure or high quality/purity “ideal gas” or “real gas” that it comprises beside CO2, also other gases which are denoted as contaminants, but preferably, the carbon dioxide comprising real gas is purified according to any of the techniques known in the art, to increase the carbon dioxide content to around 80%, which inherently meets the limitation of at least 20% CO2 in the CO2 containing gas (pg. 31, lines 26-30).
Krajete teaches the oxidation reduction potential is adjusted or maintained using a reducing agent by adjusting the hydrogen or oxygen in-gas feed into the reaction vessel (pg. 8, lines 1-3). Krajete further teaches the in-gas may have certain amounts of oxygen, and it is preferred to have a very low oxygen contamination inside reaction vessel, preferably below 2% which meets this limitation in claim 1 (pg. 44, lines 28-30). The methane produced inside the reactor is typically between 50-80% methane and may be collected and further used for energy applications which meets this limitation in claim 1 (pg. 30, lines 1-7).
The pH value inside the reactor is maintained from 5.0-8.0, by adding acid or base to control pH, well below the pH in instant claims 1 and 5 (pg. 8, line 6; pg. 49, lines 13-14). Inside the reaction vessel, the pressure may be adjusted to a value in the range from 1 bar to 500 bar absolute which significantly overlaps within the range recited in claim 12 (pg. 45, lines 1-2).
Krajete does not explicitly disclose the CO2 containing gas comprises H2S at an amount of at least 200 ppm up to 40,000 ppm as recited in claim 1. However Krajete does teach ‘real gas’ may be used as the in-gas, which means that the gas is not absolutely pure, i.e. is gas mixture, which denotes beside carbon dioxide and hydrogen comprises other gases such as hydrogen sulfide (pg. 15, para 1). A typical example for a real gas is "biogas" or also the off-gas of the method of the invention, "biogas" typically refers to a gas produced by the biological breakdown of organic matter, and can be from sources such as sewage, municipal waste, inter alia (pg. 15, para 1). As evidenced by Awe, a typical biogas composition comprises 0-4000 ppm hydrogen sulfide, which overlaps with the range recited in claim 1 (pg. 268, Table 1). Awe also discloses biogas comprises 30-40% CO2 and 0% oxygen, which also inherently meets these limitations in claim 1 (pg. 268, Table 1).
Although Krajete is silent on the effects of pH regulation in relation to hydrogen sulfide, Yan teaches hydrogen sulfide control and microbial competition in batch anaerobic digestion and the effect of initial sludge pH (title). Yan teaches high sulfur content in excess sludge impacts the production of biomethane during anaerobic digestion, mean-while leads to hydrogen sulfide (H2S) formation in biogas (abstract). Yan teaches when the initial sludge pH increased from 6.5 to 8.0, the biogas production increased by 10.1%, the methane production increased by 64.1%, while the H2S content in biogas decreased by 44.7% (abstract). Yan teaches the higher initial sludge pH inhibited the competition of sulfate-reducing bacteria with methane-producing bacteria, and thus benefitted the growth of methanogens (abstract).
Therefore it would have been prima facie obvious to one of ordinary skill in the art before the effective filing date to utilize the method of producing methane from real gas that comprises at least 20% CO2, 0-4000ppm H2S, and less than 2% oxygen contamination, while culturing methanogens with additional H2 in a stoichiometric ratio of 1:0.6 to 1.5, controlling and regulating the pH by adding a suitable acid or base, and collecting said methane as taught by Krajete, and modify the Krajete’s method by increasing the initial pH up to 8.0 to remove and reduce H2S in the resulting methane gas as taught by Yan with a reasonable expectation of success. One of ordinary skill in the art would have been motivated to increase the pH of the continuous methanogenic culture to reduce competition between sulfate-reducing bacteria and methane-producing bacteria, benefitting methanogenic growth, while simultaneously reducing H2S production as taught by Yan.
Regarding claim 3, Krajete teaches that in response to oxygen contamination of the reaction vessel, the oxidation reduction potential has to be stabilized using sulfide, such as sodium sulfide, or else, adjusting the hydrogen in-gas feed and the pH value (pg. 41, lines 27-29; pg. 8, line 2).
Regarding claim 4, Krajete teaches methanogenic microorganisms as having a biomass concentration of at least 6 g biomass per liter, wherein no additional methanogenic microorganism is added after inoculation or cell retention is applied during fermentation, which is well within the instant range (abstract). Biomass was determined as dry weight using standard drying procedures and gravimetric determination of pre-weighted glass tubes and optical density was measured using a spectrophotometer (Hitachi U-1100, Japan) at an absorption of 578 nm (pg. 55, lines 12-15).
Regarding claims 6, 7, and 9, Krajete teaches the fermentation conditions are principally the same for all methanogenic microorganisms, but in particular the species: Methanosarcinia barkeri, Methanothermobacter marburgensis, Methanobacterium thermoautotrophicus, Methanocaldococcus jannaschii, Methanothermobacter thermoautotrophicus, Methanococcus maripaludis, or mixtures thereof (pg. 60-61, sec. 7.). The methanogenic strains were anaerobically transferred into the bioreactor and maintained under anaerobic conditions (pg. 54, sec. 3.). The strains used in Krajete’s invention were obtained from a variety of environmental sources, such as anaerobic soils and sands, inter alia (pg. 25, lines 13-20). One particular strain Krajete uses is Methanothermobacter marburgensis DSM 2133 (pg. 61, sec. 7). As evidenced by DSMZ, DSM 2133 is grown on DSMZ medium 119, which consists of NaCl and NH4Cl at concentrations of 0.4 g/L, respectively, which falls within the range of the instant’s definition of a moderately saline environment of instant claim 9 (DSMZ, spec: pg. 23, lines 7-9).
Regarding claim 10, Krajete teaches an objective of the invention is the fixation of carbon dioxide which is released through industrial and agricultural processes and from industrial plants, i.e., waste carbon dioxide (pg. 3, lines 11-13). Krajete teaches the carbon dioxide gas can be ‘real gas’, wherein real gas sources delivering real gas, such as natural sources, industrial processes (industrial "waste gas") (pg. 32, lines 12-15).
Regarding claim 13, Krajete teaches the ‘off-gas’ or ‘output gas’ that is the gaseous outcome of the reaction vessel may comprise water vapor, the gases comprised in the in-gas, and methane (pg. 29, lines 21-23). During methane production
phase, the off-gas mixture mainly comprises methane, most preferably the methane content is at least 92%, 94% or 96% wherein the higher the content the more preferred (pg. 30, line 1).
Regarding claims 2 and 8, Krajete teaches the medium used to culture the bacteria provide nitrogen and salts and the bioreactor system is made anaerobic by flushing with 80%/20% (v/v) H2/CO2 for five minutes (pg. 54, lines 15-21). The reaction vessel also includes a stirrer that is adjusted for optimal high gas liquid mass transfer (pg. 44, lines 4-5). In general, the reaction volume, i.e., the culture volume, inside the reaction vessel is kept constant, so that also gaseous and/or liquid substances have to be removed from the reaction vessel depending on the total mass in-flow (pg. 45, lines 27-30). The bioreactor comprises a device for removing a liquid substance or a cell suspension from the reaction vessel (pg. 48, lines 19-20). The temperature inside the reaction vessel depends on the methanogenic microorganism which is used for the method of the invention, but in general should be in the range from 40°C to 100°C (pg. 43, lines 21-23). Krajete also teaches a standard medium for culture has the following composition: 2.1 g NH4Cl; 6.8 g KH2PO4; 3.4 g Na2CO3; 0.09 g Titriplex I; 0.04 g MgCl2 x 6H2O; 0.01 g FeCl x 4H2O; 0.2 mg CoCl2 x 6H2O; 1.2 mg NiCl2 x 6H2O; 0.2 mg NaMoO4 x 2H2O, which includes the chloride anion amounts in the range 12-300mmol/L of instant claim 8 (pg. 27, lines 23-25).
Krajete does not teach the specific range of temperature inside the bioreactor as being 32-90°C, nor the specific chloride anion range of the liquid culture medium as being 12-300mmol/L. Krajete teaches the bioreactor’s temperature to be between 40-100°C and the specific chloride anion concentration can be calculated based on the components of the medium culture composition. However, in the case where the claimed ranges overlap or lie inside ranges disclosed by the prior art is a prima facie case of obviousness (See In re Wertheim, 541 F.2d 257, 191 USPQ 90 (CCPA 1976); In re Woodruff, 919 F.2d 1575, 16 USPQ2d 1934 (Fed. Cir. 1990), MPEP 2144.05).
Response to Arguments
Applicant's arguments filed January 14, 2026 have been fully considered but they are not persuasive.
Regarding remarks directed to the rejection of claims 1-10 and 12-13 under 35 U.S.C. §103, Applicant argues there is no motivation to combine teaching of Krajete and Yan. A person of ordinary skill in the art would not have been motivated to combine the teachings of Krajete with those of Yan et al. to arrive at the claimed invention as these cited references relate to completely different technical fields. Applicant argues Krajete describes production of methane in a highly controlled gas fermentation bioreactor utilizing a pure culture of methanogenic archaea, such as Methanothermobacter marburgensis, to maximize methanogenic efficiency, and does not contain sulfate-reducing bacteria (SRB) and no biological H2S formation takes place inside the bioreactor. In contrast, Yan investigates anaerobic digestion of slaughterhouse wastewater sludge in a plant (see title and Fig. 1 on p. 2 showing the sludge digestion pathway), which is a fundamentally different environment that involves a mixed culture of microbial organisms, including sulfate-reducing bacteria (SRB), methanogens, and fermentative bacteria, growing on sulfur-rich organic substrates. The formation of H2S in Yan occurs inside the plant as a result of sulfur metabolism by the sulfate-reducing bacteria. The H2S is not introduced from external feed-gas impurities. Applicant argues the two systems do not share comparable system constraints, and are not from the same field of endeavor, thus one of ordinary skill would not be motivated to combine the two references. Applicant argues a person of ordinary skill in the art would not have been motivated to apply the pH teachings from Yan's sludge digestion because the rationale for adjusting pH in Yan addresses a completely different problem that does not occur (cannot occur) in Krajete. Yan teaches that raising the pH inhibits the sulfate-reducing bacteria (SRB), thereby preventing biological H2S formation (e.g., higher initial pH inhibited SRB and reduced H2S). This teaching is irrelevant to the system disclosed in Krajete where no SRB exists, no biological H2S is produced, and all H2S originates externally from the feed gas. Applicant argues Yan provides no guidance whatsoever for addressing the problem solved by the present invention- namely the handling of high H2S concentrations in the feed gas. In fact, Yan teaches away from the claimed invention. Yan seeks to avoid H2S formation, not operate effectively under high H2S concentrations. A person of ordinary skill in the art would understand that Yan aims to eliminate the challenge the present inventions solves. The Examiner's combination of Krajete and Yan is improper because a reference cannot be used for a purpose it does not address. Applicant argues Krajete does not address handling high H2S impurities in the feed gas, and Yan does not provide strategies for tolerating the high impurity concentrations. Applicant argues there is no hint in Krajete that pH regulation could or should be used to improve methanogenesis in the presence of H2S. Accordingly, the Examiner's assertion that pH control would represent "routine optimization" is therefore unsupported by the cited references. Applicant argues the present invention demonstrates that pH control surprisingly improves methanogenesis in the presence of high H2S concentrations. Both cited references teach or assume the opposite. Krajete treats H2S as an undesirable impurity. Yan teaches that H2S inhibits methanogenesis and its solution is preventing H2S formation by suppressing SRB activity. Neither Krajete nor Yan provide any hint that methanogenesis could be improved under high H2S concentrations - they suggest the opposite. The present invention demonstrates that pH control achieves an unexpected technical effect of increasing methanogenic performance under elevated H2S concentrations that neither cited reference suggests or predicts.
In response to applicant’s argument that there is no teaching, suggestion, or motivation to combine the references, the examiner recognizes that obviousness may be established by combining or modifying the teachings of the prior art to produce the claimed invention where there is some teaching, suggestion, or motivation to do so found either in the references themselves or in the knowledge generally available to one of ordinary skill in the art. See In re Fine, 837 F.2d 1071, 5 USPQ2d 1596 (Fed. Cir. 1988), In re Jones, 958 F.2d 347, 21 USPQ2d 1941 (Fed. Cir. 1992), and KSR International Co. v. Teleflex, Inc., 550 U.S. 398, 82 USPQ2d 1385 (2007). In this case, Krajete teaches the claimed method of providing CO2 biogas that comprises H2S and O2, specifically addressing the CO2:H2 stoichiometric ratio for efficient methane production. Although Krajete does not specifically address the limitations in relation to H2S contamination and regulating pH below 10, Krajete does teach pH probes measure the bioreactor, and acid or base is added by titration to control pH as desired. Further Krajete does teach the limitation of keeping the pH value below 10, and kept at a constant of 6.8 using 1M (NH4)2CO3 as base in order to compensate for acidification of the medium during growth of M. marburgensis (pg. 26, para 1). Yan teaches increased H2S may be produced in the biogas, causing many problems, such as inhibition of anaerobic digestion process, decrease of biogas production and methane content, and that by regulating and controlling the pH, methane production was increased and H2S contamination was decreased in the resulting biogas (pg. 68, col. 1, para 2; pg. 73, sec. 4.). Thus, Yan reference teaches a motivation to control and regulate the pH below 10, in relation to high levels of hydrogen sulfide contamination. Further, regarding Applicant’s argument that Krajete’s invention is based on a pure M. marburgensis culture, and not a mixture of SRB and methanogens as in Yan, and therefore would not be obvious, the test for obviousness is not whether the features of a secondary reference may be bodily incorporated into the structure of the primary reference; nor is it that the claimed invention must be expressly suggested in any one or all of the references. Rather, the test is what the combined teachings of the references would have suggested to those of ordinary skill in the art. See In re Keller, 642 F.2d 413, 208 USPQ 871 (CCPA 1981). Thus, Krajete provides a teaching of feeding biogas (with CO2 and H2S), adjusting the stoichiometric ratio, and regulating the pH value below 10, for efficient methane production, and Yan teaches high H2S concentrations in fermentative sludge can be reduced by specifically controlling to a pH of 8, thereby increasing methane production and decreasing H2S contamination in the biogas. Furthermore, Applicant’s contended unexpected results of regulating the pH below 10 in the presence of high H2S contamination in the claimed process would be expected based on the teachings of Yan. Thus, it would have been prima facie obvious to modify the method taught by Krajete, by increasing/regulating the initial pH to 8.0 to remove and reduce H2S contamination in the resulting methane gas as taught by Yan with a reasonable expectation of success.
Conclusion
THIS ACTION IS MADE FINAL. Applicant is reminded of the extension of time policy as set forth in 37 CFR 1.136(a).
A shortened statutory period for reply to this final action is set to expire THREE MONTHS from the mailing date of this action. In the event a first reply is filed within TWO MONTHS of the mailing date of this final action and the advisory action is not mailed until after the end of the THREE-MONTH shortened statutory period, then the shortened statutory period will expire on the date the advisory action is mailed, and any nonprovisional extension fee (37 CFR 1.17(a)) pursuant to 37 CFR 1.136(a) will be calculated from the mailing date of the advisory action. In no event, however, will the statutory period for reply expire later than SIX MONTHS from the mailing date of this final action.
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/LOUISE W HUMPHREY/Supervisory Patent Examiner, Art Unit 1657
/JESSICA EDWARDS/
Examiner, Art Unit 1657
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