OPTIMISED FERMENTATION MEDIA
The invention relates to improvements in the production of alcohols by microbial fermentation, particularly to production of alcohols by microbial fermentation of a substrate comprising CO. It more particularly relates to the provision of an inorganic organic sulfur source to a fermentation system such that one or more micro-organisms convert a substrate comprising CO to alcohols. In a particular embodiment, a microbial culture is provided with sodium polysulfide, wherein a substrate comprising CO is converted to products including ethanol and 2,3-butanediol.
1 . A method of improving efficiency of fermentation of a substrate including CO to produce one or more products, the method comprising:
providing inorganic sulfur to a fermentation broth that includes one or more carboxydotrophic micro-organisms.
2 . The method of claim 1 , wherein the products include one or more alcohols and/or acids.
3 . (canceled)
4 . (canceled)
5 . The method of claim 1 , wherein the products include ethanol and/or 2,3-butanediol.
6 . (canceled)
7 . The method of claim 5 , wherein ethanol and 2,3-butanediol are produced in a ratio of less than 10:1.
8 . (canceled)
9 . (canceled)
10 . The method of claim 1 , wherein inorganic sulfur is provided in the fermentation broth at a predetermined concentration.
11 . A method of producing one or more products by microbial fermentation, the method comprising of:
(a) providing a substrate comprising carbon monoxide;
(b) in a bioreactor containing a culture of one or more micro-organisms in a liquid nutrient medium that includes one or more inorganic sulfur compounds, anaerobically fermenting the substrate to produce one or more products that include acids and/or alcohols;
(c) capturing and recovering the one or more products produced;
wherein the concentration of one or more inorganic sulfur compounds in the culture is maintained at a predetermined concentration or within a predetermined concentration range during at least step (b).
12 . The method of claim 11 , wherein the one or more inorganic sulfur compounds is adapted to release one or more sulfur containing species into the liquid nutrient medium.
13 . (canceled)
14 . The method of claim 11 , wherein the alcohol is ethanol and the acid is acetate, and wherein the ethanol-to-acetate ratio is at least 10:1.
15 . The method of claim 11 , wherein the alcohol is ethanol and the acid is acetate, and wherein the ethanol is substantially produced without concomitant acetate.
16 . The method of claim 11 , wherein inorganic sulfur is provided within a predetermined concentration range of about 1 mM to about 20 mM.
17 . (canceled)
18 . The method of claim 11 , wherein inorganic sulfur is provided as a polysulfide solution.
19 . (canceled)
20 . The method of claim 11 , wherein the substrate comprising CO, comprises at least about 15% to about 100% CO by volume.
21 . The method of claim 11 , wherein the substrate comprising CO, comprises at least about 40% to about 70% CO by volume.
22 . The method of claim 11 , wherein the substrate comprises a gas obtained from a steel mill.
23 . The method of claim 11 , wherein the micro-organism are selected from the group consisting of Clostridium, Moorella, Pyrococcus, Eubacterium, Desulfobacterium, Carboxydothermus, Acetogenium, Acetobacterium, Acetoanaerobium, Butyribaceterium and Peptostreptococcus.
24 . The method of claim 23 , wherein the micro-organism is Clostridium autoethanogenum.
25 . A nutrient medium adapted to improve microbial growth and/or production of metabolites by one or more carboxydotrophic micro-organisms, the nutrient medium comprising one or more inorganic sulfur compounds.
26 . The nutrient medium of claim 25 , wherein the medium further comprises about 1 mM to 20 mM polysulfide.
27 . The nutrient medium of claim 26 , further including one or more of Mn, Zn, B, Mo, Se, V, W, Fe, Co and/or Ni.
28 . (canceled)
29 . The method of claim 11 , wherein the substrate further comprises carbon dioxide and/or hydrogen.