Method for the production of lactic acid or a salt thereof by simultaneous saccharification and fermentation of starch

Abstract

The present invention pertains to a method for the production of lactic acid or a salt thereof wherein starch is subjected to a process of simultaneous saccharification and fermentation, the method comprising saccharifying starch in a medium comprising at least a glucoamylase and simultaneously fermenting the starch using a microorganism, and optionally isolating lactic acid from the medium, characterized in that a moderately thermophilic lactic acid-producing microorganism is used. The invention further relates to a method of performing said process in the presence of a moderately thermophilic lactic acid producing microorganism, which has been adapted to have its maximum performance at the working pH.

1 . A method of producing lactic acid or a salt thereof, wherein starch is subjected to a process of simultaneous saccharification and fermentation, the method comprising:
 saccharifying starch in a medium comprising at least a glucoamylase;   simultaneously fermenting the starch by using a moderately thermophilic lactic acid-producing microorganism; and   optionally isolating lactic acid from the medium;   
       wherein:
 the moderately thermophilic lactic acid-producing microorganism is derived from a strain of  Bacillus coagulans, Bacillus smithii , or from a mixture thereof. 
 
     
     
         2 . The method according to  claim 1 , wherein the starch is saccharified, fermented, and optionally liquefied, in a mixture of glucoamylase and at least one of pullulanase and α-amylase. 
     
     
         3 . The method according to  claim 1 , wherein the lactic acid or a salt thereof has an enantiomeric purity of at least 95%. 
     
     
         4 . The method according to  claim 1 , wherein the process is performed at pH 3-8.5. 
     
     
         5 . The method according to  claim 4 , wherein the process is performed at pH 5-6. 
     
     
         6 . The method according to  claim 5 , wherein the process is performed at pH 5.35-5.80. 
     
     
         7 . The method according to  claim 6 , wherein the process is performed at pH 5.50-5.60. 
     
     
         8 . The method according to  claim 1 , wherein the microorganism is adapted to a pH range at which the process is performed. 
     
     
         9 . The method according to  claim 1 , wherein the microorganism is adapted to a pH range of 5-5.80. 
     
     
         10 . The method according to  claim 1 , wherein the process is performed at 30-70° C. 
     
     
         11 . The method according to  claim 10 , wherein the process is performed at 40-60° C. 
     
     
         12 . The method according to  claim 11 , wherein the process is performed at 50-60° C. 
     
     
         13 . The method according to  claim 2 , wherein the glucoamylase or the mixture of glucoamylase and at least one of pullulanase and α-amylase is added in at least two portions.