Low pH lactic acid fermentation

Abstract

A process for producing lactic acid which includes incubating acid-tolerant homolactic bacteria in nutrient medium to produce a fermentation broth with high levels of free lactic acid is provided. An isolated acid-tolerant homolactic bacteria capable of producing high levels of free lactic acid is also provided.

1 . A process for producing lactic acid comprising: 
 incubating an acid-tolerant homolactic bacteria in nutrient medium to generate a solution including at least about 25 g/L free L-lactic acid or at least 25 g/L free D-lactic acid.    
   
   
       2 . The process of  claim 1  comprising incubating the bacteria in the nutrient medium to generate a solution including at least about 40 g/L L-lactate at a final incubation pH of no more than about 4.0.  
   
   
       3 . The process of  claim 1  comprising incubating the bacteria at a temperature of at least about 47° C.  
   
   
       4 . The process of  claim 1  wherein the nutrient medium comprises corn steep water.  
   
   
       5 . The process of  claim 1  wherein the nutrient medium comprises at least about 50 g/L carbohydrate which includes glucose, fructose, galactose, melibiose, sucrose, raffinose, stachyose, or a mixture thereof.  
   
   
       6 . The process of  claim 1  wherein the nutrient medium comprises base.  
   
   
       7 . The process of  claim 1  wherein the nutrient medium comprises a lactate salt.  
   
   
       8 . The process of  claim 1  comprising incubating the bacteria in the nutrient medium to produce L-lactate having an optical purity of at least about 50%.  
   
   
       9 . The process of  claim 1  comprising incubating the bacteria in the nutrient medium to produce free lactic acid at a overall rate of at least about 0.5 g/L/hr.  
   
   
       10 . The process of  claim 1  comprising incubating the bacteria at a temperature of at least about 47° C. to generate a solution including at least about 30 g/L free L-lactic acid; 
 wherein the nutrient medium includes (i) at least about 25 g/L corn steep water dry solids, (ii) at least about 50 g/L glucose, fructose, or a mixture thereof, and (iii) at least about 20 g/L CaCO 3 .    
   
   
       11 . The process of  claim 10  wherein the nutrient medium further comprises yeast extract.  
   
   
       12 . The process of  claim 10  wherein the nutrient medium further comprises nonionic surfactant.  
   
   
       13 . The process of  claim 1  comprising incubating the bacteria in the nutrient medium at an average incubation pH of no more than about 4.2.  
   
   
       14 . Acid-tolerant homolactic bacteria capable of generating a solution including at least about 25 g/L free L-lactic acid or at least about 25 g/L free D-lactic acid.  
   
   
       15 . The homolactic bacteria of  claim 14  wherein said bacteria are rodshaped, gram positive, air indifferent bacteria.  
   
   
       16 . The homolactic bacteria of  claim 14  wherein said bacteria is capable of producing L-lactate having an optical purity of at least about 80%.  
   
   
       17 . The homolactic bacteria of  claim 14  wherein said bacteria is capable of generating a solution including at least about 80 g/L L-lactate at an incubation temperature of at least about 47° C. and an average incubation pH of no more than about 4.2.