Alcohol production process

Abstract

The invention relates to the production of products such as alcohols and acids by microbial fermentation, particularly microbial fermentation of substrates comprising CO. It more particularly relates to methods and systems for improving efficiency of production products by microbial fermentation. In particular embodiments, the invention provides a method of controlling substrate supply, such that production of desired metabolites is optimised.

1 - 27 . (canceled) 
     
     
         28 . A method of optimizing supply of a CO-containing substrate to a bioreactor for fermentation to produce products including one or more alcohol(s) and/or acid(s) by a culture of one or more carboxydotrophic micro-organisms, said method comprising:
 determining acid production at first and second time points,   detecting a change in acid production between said first and second time points, and   changing the rate of substrate supply in response to detection of a a change in acid production.   
     
     
         29 . The method of  claim 28 , wherein an increase in acid level between the first and second time points results in an increase in substrate supply. 
     
     
         30 . The method of  claim 28 , wherein a decrease in acid level between the first and second time points results in a decrease in substrate supply. 
     
     
         31 . The method of  claim 28 , wherein the micro-organism is selected from the group consisting of  Clostridium, Moorella, Pyrococcus, Eubacterium, Desulfobacterium, Carboxydothermus, Acetogenium, Acetobacterium, Acetoanaerobium, Butyribaceterium  and  Peptostreptococcus.    
     
     
         32 . The method of  claim 28 , wherein the micro-organism is selected from the group consisting of  Clostridium autoethanogenum, Clostridium ljungdahli, Clostridium ragsdalei  and  Clostridium carboxydivorans.    
     
     
         33 . A method of increasing efficiency of fermentation of a CO-containing substrate in a bioreactor by a culture of one or more carboxydotrophic microorganisms, to produce products including acid(s) and/or alcohol(s), the method comprising:
 providing the substrate such that acid levels are maintained between predetermined threshold concentrations in the bioreactor.   
     
     
         34 . The method of  claim 33 , wherein providing the substrate comprises providing a substrate supply at or towards an optimum level by maintaining a substantially constant alcohol-to-acid ratio. 
     
     
         35 . The method of  claim 33 , further comprising maintaining acid levels between predetermined threshold concentrations of 1-10 g/L fermentation broth. 
     
     
         36 . The method of  claim 35 , further comprising maintaining acid levels between predetermined threshold concentrations of 2-8 g/L fermentation broth. 
     
     
         37 . The method of  claim 33 , further comprising determining acid levels by measuring pH of the culture. 
     
     
         38 . The method of  claim 33 , wherein the fermentation is continuous. 
     
     
         39 . The method of  claim 33 , wherein products are produced in a ratio of at least 2:1 alcohol(s) to acid(s). 
     
     
         40 . The method of  claim 33 , wherein the acid is acetate. 
     
     
         41 . The method of  claim 33 , wherein the alcohol is ethanol. 
     
     
         42 . The method of  claim 33 , wherein the substrate comprises a gas obtained as a by-product of an industrial process selected from the group consisting of ferrous metal products manufacturing, non-ferrous products manufacturing, petroleum refining processes, gasification of biomass, gasification of coal, electric power production, carbon black production, ammonia production, methanol production and coke manufacturing. 
     
     
         43 . The method of  claim 33 , wherein the CO-containing substrate comprises at least about 15% to about 95% CO by volume. 
     
     
         44 . The method of  claim 33 , wherein the micro-organism is selected from the group consisting of  Clostridium, Moorella, Pyrococcus, Eubacterium, Desulfobacterium, Carboxydothermus, Acetogenium, Acetobacterium, Acetoanaerobium, Butyribaceterium  and  Peptostreptococcus.    
     
     
         45 . The method of  claim 33 , wherein the micro-organism is selected from the group consisting of  Clostridium autoethanogenum, Clostridium ljungdahli, Clostridium ragsdalei  and  Clostridium carboxydivorans.    
     
     
         46 . A system for using microbial fermentation to produce products, said system comprising:
 a bioreactor configured to conduct fermentation of a CO-containing substrate;   determining means for determining acid level in the bioreactor; and   controlling means for controlling a supply of a CO-containing substrate;   wherein, the controlling means is configured to control supply of a CO-containing substrate in response to a determination of the acid level in the bioreactor.   
     
     
         47 . A system according to  claim 46 , wherein the determining means is configured to determine an acid level by measuring an amount of one or more acids produced, or by measuring a pH of a fermentation broth.