Methods of sustaining culture viability

Abstract

The present invention relates to methods for sustaining a microbial culture during periods of limited substrate supply. In accordance with the methods of the invention a microbial culture comprising carboxydotrophic bacteria can be sustained during periods of limited substrate supply by maintaining the temperature of the microbial culture at a temperature below an optimum operating temperature.

1 - 24 . (canceled) 
     
     
         25 . A method of sustaining viability of a microbial culture of carboxydotrophic bacteria when a substrate that includes CO is limited or unavailable, said method comprising maintaining the culture substantially at a temperature or within a temperature range below an optimum operating temperature of the culture. 
     
     
         26 . The method of  claim 25 , wherein maintaining the culture comprises maintaining the temperature at least 5° C. below the optimum operating temperature. 
     
     
         27 . The method of  claim 25 , further comprising maintaining the temperature of the microbial culture substantially at the optimum operating temperature if the substrate comprising CO becomes non-limited. 
     
     
         28 . The method of  claim 25 , wherein the microbial culture is in liquid nutrient media in a bioreactor. 
     
     
         29 . The method of  claim 28 , further comprising cooling the bioreactor such that the temperature of the liquid nutrient media is maintained at a temperature below the optimum operating temperature. 
     
     
         30 . The method of  claim 25 , further comprising sustaining viability of the culture over a period of limited CO availability of at least 3 hours. 
     
     
         31 . The method of  claim 25 , wherein the carboxydotrophic bacteria is selected from the group consisting of  Clostridium, Moorella, Pyrococcus, Eubacterium, Desulfobacterium, Carboxydothermus, Acetogenium, Acetobacterium, Acetoanaerobium, Butyribaceterium  and  Peptostreptococcus.    
     
     
         32 . The method of  claim 25 , wherein the carboxydotrophic bacteria is  Clostridium autoethanogenum.    
     
     
         33 . The method of  claim 25 , 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. 
     
     
         34 . The method of  claim 25 , wherein the substrate that includes CO comprises at least about 15% to about 100% CO by volume. 
     
     
         35 . A method of sustaining viability of a microbial culture of carboxydotrophic bacteria during storage, said method comprising:
 cooling the microbial culture to a temperature or temperature range below an optimum operating temperature; and   storing the microbial culture under limited CO conditions for a selected period of time.   
     
     
         36 . The method of  claim 35 , further comprising returning the culture to the optimum operating temperature under non-limited CO conditions. 
     
     
         37 . The method of  claim 35 , wherein storing the microbial culture comprises storing the microbial culture for at least 5 hours. 
     
     
         38 . The method of  claim 37 , further comprising transporting the microbial culture to a remote location during storage. 
     
     
         39 . The method of  claim 37 , further comprising inoculating the bioreactor with the microbial culture following storage. 
     
     
         40 . The method of  claim 35 , wherein the carboxydotrophic bacteria are selected from the group consisting of  Clostridium, Moorella, Pyrococcus, Eubacterium, Desulfobacterium, Carboxydothermus, Acetogenium, Acetobacterium, Acetoanaerobium, Butyribaceterium  and  Peptostreptococcus.    
     
     
         41 . The method of  claim 35 , wherein the carboxydotrophic bacteria is  Clostridium autoethanogenum.    
     
     
         42 . A system for fermentation of a substrate comprising CO, said system comprising:
 at least one bioreactor;   determining means adapted to determine whether a supply of a CO-containing substrate that is provided to a microbial culture is limited or non-limited; and   temperature control means configured such that, in use, the temperature of the bioreactor can be adjusted in response to determination of whether the supply of the CO-containing substrate for the microbial culture is limited or non-limited.   
     
     
         43 . The system of  claim 42 , wherein the temperature control means is configured to reduce the temperature of the bioreactor if the determining means determines that the supply of the CO-containing substrate is limited. 
     
     
         44 . The system of  claim 43 , wherein the system further comprises processing means configured such that the temperature of the bioreactor can be automatically regulated in response to changes in whether the supply of the CO-containing substrate is limited or non-limited.