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 products by microbial fermentation. In particular embodiments, the invention provides a method of optimising production of desired products including the step of ascertaining the proportion of CO converted to CO2.

1 .- 23 . (canceled) 
     
     
         24 . A method of improving efficiency of microbial fermentation of a substrate that includes CO, said method comprising:
 providing the substrate to a microbial culture such that
 a first proportion of CO is fixed as one or more desired products including acid(s) and/or alcohol(s), and 
 a second proportion of CO is converted to CO 2 , 
   wherein determination of the proportion of CO converted to CO 2  is used to determine a substrate supply rate for production of the one or more desired products.   
     
     
         25 . The method of  claim 24 , wherein providing the substrate comprises providing the substrate at a supply rate that is:
 i. increased if the proportion of CO converted to CO 2  is determined to be below an optimal value or range; or   ii. decreased if the proportion of CO converted to CO 2  is determined to be above an optimal value or optimal range; or   iii. maintained if the proportion of CO converted to CO 2  is determined to be substantially at an optimal value or within an optimal range.   
     
     
         26 . The method of  claim 25 , further comprising automatically adjusting the substrate supply rate such that the proportion of CO converted to CO 2  is maintained substantially at an optimal value or range. 
     
     
         27 . The method of  claim 24 , wherein the substrate comprising CO comprises less than 5% H 2  by volume. 
     
     
         28 . The method of  claim 24 , wherein a desired product is ethanol. 
     
     
         29 . A method of improving the efficiency of producing one or more acids and/or alcohols by microbial fermentation of a substrate comprising CO under predetermined operating parameters, said method comprising
 determining a proportion of carbon directed towards one or more products, and   depending on the determination, either:
 i. making an adjustment to one or more operating parameters, such that the proportion of carbon fixed as a desired product increases; or 
 ii. maintaining the operating parameters, such that the proportion of carbon fixed as a desired product remains substantially constant. 
   
     
     
         30 . The method of  claim 29 , wherein the operating parameter(s) are selected from a group consisting of:
 pH of the fermentation broth;   redox potential of the fermentation broth;   CO concentration of the fermentation broth;   rate of substrate supply;   composition of the substrate stream;   pressure of the substrate stream;   fermentation broth agitation rate;   product removal rate;   acid and/or alcohol concentration of the fermentation broth;   one or more nutrients in the liquid nutrient medium; and   rate of supply of one or more nutrients.   
     
     
         31 . The method of  claim 29 , wherein the proportion of carbon fixed as one or more products is established by determining the proportion of CO converted to CO 2 . 
     
     
         32 . The method of  claim 29 , wherein the alcohol is ethanol and the ethanol is produced continuously. 
     
     
         33 . The method of  claim 29 , wherein the substrate comprising CO, comprises at least about 15% to about 100% CO by volume. 
     
     
         34 . The method of  claim 29 , wherein the fermentation is carried out by a micro-organism selected from the group consisting of  Clostridium, Moorella, Pyrococcus, Eubacterium, Desulfobacterium, Carboxydothermus, Acetogenium, Acetobacterium, Acetoanaerobium, Butyribaceterium  and  Peptostreptococcus.    
     
     
         35 . The method of  claim 34 , wherein the micro-organism is  Clostridium autoethanogenum.    
     
     
         36 . The method of  claim 24 , wherein the fermentation is carried out by a micro-organism selected from the group consisting of  Clostridium, Moorella, Pyrococcus, Eubacterium, Desulfobacterium, Carboxydothermus, Acetogenium, Acetobacterium, Acetoanaerobium, Butyribaceterium  and  Peptostreptococcus.    
     
     
         37 . The method of  claim 36 , wherein the micro-organism is  Clostridium autoethanogenum.    
     
     
         38 . A system for the microbial fermentation of a substrate stream that includes CO to yield products that include acid(s) and/or alcohol(s), said system comprising:
 a bioreactor containing, in use, a microbial culture;   measuring means adapted to determine a proportion of carbon fixed as a particular product; and   at least one adjustment means adapted to make one or more adjustments to the microbial culture and/or the substrate stream.   
     
     
         39 . A system according to  claim 38 , wherein the measuring means comprises means for determining the composition of an exhaust stream exiting the bioreactor. 
     
     
         40 . A system according to  claim 39 , wherein the measuring means is further adapted to determine the composition of a substrate stream entering the bioreactor. 
     
     
         41 . A system according to  claim 38 , wherein the adjustment means are configured to make one or more adjustments if the determining means determines that the proportion of carbon fixed as a desired product has deviated from a predetermined value or range. 
     
     
         42 . A system according to  claim 41 , wherein the adjustment means are configured to make adjustments by one or more of the following:
 changing pH of the fermentation broth;   changing redox potential of the fermentation broth;   changing CO concentration of the fermentation broth;   changing H 2  concentration of the fermentation broth;   changing composition of the substrate stream;   changing pressure of the substrate stream;   changing fermentation broth agitation rate;   product removal;   changing acid and/or alcohol concentration of the fermentation broth;   changing one or more nutrients in the liquid nutrient medium; and   changing rate of supply of one or more nutrients.   
     
     
         43 . A system according  claim 38 , further comprising processing means adapted to control one or more adjustment means such that one or more adjustment(s) can be made to the microbial culture and/or substrate stream if it is determined that the proportion of carbon fixed as a desired product has deviated from a predetermined value or range.