Solvent tolerant microorganisms and methods of isolation

Abstract

Enterococcus bacteria having enhanced tolerance to butanols have been isolated. The bacteria are useful for the fermentive production of butanol. New methods for the isolation of butanol tolerant Enterococcus are also provided.

1 . A method for the isolation of a butanol tolerant microorganism comprising:
 a) providing a microbial sample comprising a microbial consortium;   b) contacting the microbial consortium with a growth medium comprising a fermentable carbon source until the members of the microbial consortium are growing;   c) contacting the growing microbial consortium of step (b) with butanol; and   d) isolating the viable members of step (c) wherein a butanol tolerant microorganism is isolated.   
     
     
         2 . A method according to  claim 1  wherein the growing consortium of step (b) are growing in log phase. 
     
     
         3 . A method according to  claim 1  wherein after step (c) the consortium is plated on solid medium. 
     
     
         4 . A method according to  claim 3  wherein the solid medium contains butanol. 
     
     
         5 . A method according to  claim 1  wherein the contacting of step (c) is repeated one or more times. 
     
     
         6 . A method according to  claim 1  wherein the butanol concentration of the contacting step (c) is from about 0.8% w/v to about 3.0% w/v. 
     
     
         7 . A method according to  claim 1  wherein the isolating of step (d) comprises the steps of:
 i) growing the viable members of step (d) in a liquid medium in the absence of butanol; whereby the viable members multiply;   ii) growing the cells of step (i) in the presence of butanol; and   iii) collecting the cells of step (ii) that grow in the presence of butanol wherein a butanol tolerant microorganism is isolated.   
     
     
         8 . A method according to  claim 1  wherein the fermentable carbon source is selected from the group consisting of sucrose, fructose, glucose, butyric acid, valeric acid and mixtures thereof. 
     
     
         9 . A method according to  claim 1  wherein the butanol is predominantly 1-butanol, predominantly 2-butanol, or predominantly isobutanol. 
     
     
         10 . A method according to  claim 1  wherein the consortium is grown under anaerobic conditions. 
     
     
         11 . A method according to  claim 1  wherein the consortium is grown under microaerophilic conditions. 
     
     
         12 . A method according to  claim 1  wherein the consortium is grown under aerobic conditions. 
     
     
         13 . A method according to  claim 1  wherein the viable members of step (d) are tolerant to at least 2.5% w/v 1-butanol when grown on a solid medium at 37° C. 
     
     
         14 . A method according to  claim 1  wherein the viable members of step (d) are tolerant to at least 3.9% w/v 2-butanol when grown on a solid medium at 37° C. 
     
     
         15 . A method according to  claim 1  wherein the viable members of step (d) are tolerant to at least 2.7% w/v isobutanol when grown on a solid medium at 37° C. 
     
     
         16 . A method according to  claim 1  wherein the viable members of step (d) are tolerant to at least 5.0% w/v 2-butanone when grown on a solid medium at 37° C. 
     
     
         17 . A method according to  claim 1  wherein the viable members of step (d) are tolerant to at least 9.0% w/v ethanol when grown on a solid medium at 37° C. 
     
     
         18 . A method according to  claim 1  wherein the microbial sample is an environmental sample. 
     
     
         19 . A method according to  claim 1  wherein the butanol tolerant microorganism is an  Enterococcus  sp.